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An Introduction to BTnut Applications

1. AT I ee FE foe Dee mi Tm te i 5 Ei L3 rt et X4 5 Fa eu cb cb O Or E n 4 P m eh C8 63 1 l ok a a m EBBB ij Rd i nl eb E 28 25 He BTnode 3 22 ETH Figure 2 3 B Tnode rev3 top assembly and connector pinout 2 4 BTnut System Software Resources First we will make you familiar with the development environment and the tool flow The exercises in this section are based on using Eclipse and CDT yet they can also be performed using other project management environments and editors Explanation Getting to know the BTnut system software release The BTnut software is released in both a binary snapshot and sourcecode format The most recent releases can be downloaded from sourceforge net e The btnode_snap_btnode3_binary contains an out of the box pre compiled library package for AVR binary and documentation ready for usage with the avr gcc toolchain and the demo applications included e The package btnut system contains all BTnut and Nut OS sources It requires to compile the B Tnut system software and install the documentation prior to the compilation of applications The releases are numbered even and are based on the following CVS tag and date BTnut snapshot and release REL VERSION 1 8 Nut OS NUT SNAPSHOT 2007 01 23 and compiles against the following avr libc AVR Libc avr libc 1 4 3 The BTnut pre compil
2. E OR 7S UT I TT WwW 562 7 2e 95 g h Et fut w w xu S int i for i 0 i lt 128 i if character alphabet i my 67 6 257 Q gt 009 gt n 00 Q 0 0Q 09 59 9 009 9 o CF ND 0 2 309 009 2 2 022 0 0 27 8 292 07 9 0 2 029 0 0 09 Rp 7 P K L NW N 70 P Q gt Y OZ 00 009 009 7009 0 a b jj k 015 7m 70 p r Q 009 09 Q9 9 no valid character sum int pow double 2 double length 1 i return i return 1 int bin2int char binary int i int sum 0 int length length strlen binary for i 0 i lt length i if binary i 1 sum 0x01 lt lt length 1 i return sum void process_message char message_str char message char buffer 8 0 int length int i 8 4 SENDING AN SMS MESSAGE USING AT COMMANDS 65 int character 1 char base 8 0 char carry 8 0 char rdbuffer 8 0 init message str 0 0 length strlen message if length lt 15 Strcat message str 00000 else if length gt 160 length 160 strcat message_str 0000 itoa length buffer 16 convert integer to hex string strcat message str
3. int ution 3 4 lude lt hardware btn hardware h gt OMPUTE ADC values corresponding to 1 and 2 Volts f battery voltage is 1V the BAT SENSE signal is 0 5V he reference voltage is 3 3V and corresponds to the ADC value 1024 herefore 0 5V corresponds to an ADC value of 1024 3 3 0 5 155 battery voltage is 2V ADC value is 310 ine BAT 1 VOLT 155 ine BAT 2 VOLT 310 Shortpause u short duration u short i for i 0 i lt duration i 1 d pause u short duration u short i for i 0 i lt duration i 1 shortpause Oxffff write_led u_char value volatile u_char pointer u_char dummy pointer u_char u_short value lt lt 8 dummy pointer sbi PORTB 5 asm volatile nop cbi PORTB 5 get battery voltage void int result ADMUX 1 lt lt MUXO ADMUX 1 lt lt MUX1 ADCSRA 1 lt lt ADPSO ADCSRA 1 lt lt ADPS1 ADCSRA 1 lt lt ADPS2 ADCSRA 1 lt lt ADEN ADCSRA 1 lt lt ADSC while ADCSRA amp 1 lt lt ADSC result ADCL 97 result ADCH lt lt 8 return result int main void t int battery voltage 0 DDRB 1 lt lt DDB5 while 1 battery voltage get battery voltageO if battery voltage lt BAT 1 VOLT write led 0x02 else if battery_voltage lt BAT_2_VOLT write_led 0x04 else write_led 0x08 T pause 12 write_led 0x01 pause 12 return 0 Solution 3 5
4. THE ADVANTAGE of the CTC over the solution for ex 23 is that the interval can be adjusted more precisely In the previous mode you loose the time that elapses between the moment the interrupt is triggered and the moment the timer registers are reset while 1 if toggle toggle 0 write led 0x01 else toggle 1 write_led 0x00 pause 10 return 0 Solution 3 7 In my case i measured an execution time of 0 25 ms without printf and 1 2 ms with printf Solution 3 9 include lt hardware btn hardware h gt include lt dev irqreg h gt include lt stdio h gt freopen include lt io h gt _ioctl include lt dev usartavr h gt NutRegisterDevice APP_UART UART_SETSPEED include lt sys timer h gt COMPUTE ADC values corresponding to 1 and 2 Volts If battery voltage is 1V the BAT_SENSE signal is 0 5V The reference voltage is 3 3V and corresponds to the ADC value 1024 Therefore 0 5V corresponds to an ADC value of 1024 3 3 0 5 155 A battery voltage is 2V ADC value is 310 define BAT_1_VOLT 155 define BAT_2_VOLT 310 int adc_done 0 int battery_voltage 0 void shortpause u_short duration 1 u_short i for i 0 i lt duration i i void pause u_short duration u_short i for i 0 i lt duration i shortpause Oxffff void write_led u_char value volatile u_char pointer u_char dummy pointer u_char
5. Bluetooth MAC address 00 04 3f 00 00 d2 HCI version 2 00C9 2 0012 003D LMP features 03 10 00 FF FF 05 F8 1B Local name ZeevoEmbeddedDevice hit tab twice for a list of commands bt cmd 00 d2 bt led bat nut log bt cmd 00 d2 There are NutOS BTnode and Bluetooth specific commands if called without arguments they will show hints on the correct syntax where applicable bt bluetooth radio commands led toggle LED patterns bat get the battery status nut show OS system information log BTnut logging features For reference on Bluetooth 6 see the support documents and links provided on the BTnode web page see section 11 4 Exercise 2 17 To simplify the building and uploading we will now create Make Targets in Eclipse that you can execute with a single click Open the Make Targets View Window Show View Other Make and navigate to the app bt cmd folder Right click onto this folder and select Add Make Target Alternatively you can create different targets by entering make arguments such as all btnode3 version or clean Then use these Make Targets to automatically build and upload selected applications from within Eclipse You can observe the progress and console output from the respective views Exercise 2 18 Right click onto the bt cmd c file in the C C Projects View and select Compare With Local History to see the changes you have made earlier Exercise 2 19 Cre
6. read from prev saved context printf d n val NutSleep 1000 Optional Exercise 10 6 Reimplement ez 10 5 using the adc2 h library referenced above How does the library support ADC context switches Locate the source code of adc2 c and look up 10 3 Reading Sensor Data Depending on the type of sensor that we want to read out different reading strategies might be appropriate 10 3 1 Polling Polling is the simplest yet least efficient way of reading sensor values The simplest way would be to wrap the reading in a loop potentially in a separate thread in order to allow the main program to continue executing other tasks However this approach ties up a lot of processing power and uses up precious energy when running under battery power In most cases one would want to at least include a NutSleep statement within the loop to ensure that sensor readings only happen seconds or minutes apart not milliseconds e g for recording light or temperature values across several hours Instead of looping and repeatedly calling NutSleep we can also let BTnut do the work for us by using the NutTimerStart function described in section above By utilizing B Tnut timers repeated requests for sensor data can be scheduled over the course of hours days or even weeks Given the 32 bit resolution of the NutTimerStart function both one shot and periodic timers of up to 49 days can be installed 10 3 2 Interrupts BTnut time
7. 79 BO 4C 4F BB CF 73 90 59 FE 6 83 E8 E8 32 48 48 75 BF C9 65 17 length of the SMS carrier address 00 selects the number stored on the phone s SIM card message flags use 25 message reference number 00 lets the phone set the reference number length of the destination address number of digits in hex format OB format of the destination address use 91 for international format i e 41 destination address each digit of the phone number represents half of a Byte Therefore if the length of the phone number is odd a trailing F has to be added to complete the last Byte The destination address is generated out of the phone number by flipping every Byte s lower and upper half So the destination address from the example represents the phone number 41774163126 The sign is omitted protocol identifier use 00 data coding scheme use 00 length of the original message this is the number of characters at most 160 of the message string including spaces in hex format encoded message the original message is coded using a 7bit ASCII character set The stream of 7bit characters is then encoded into a Byte stream to form the encoded message The coding scheme is depicted in the following formalism Definitions length of message string n element of message string O lt k lt n 1 character k X Xs Xo character k 1 Y Ys Yo Encoding if k 4 1 mod 8 Z0 Yk mod 8 Yo X6 Xk mod 8 I N k mod 8 1 bit 7 k m
8. Insert a wait e g NutSleep 5000 after sending the PDU if you would like to observe the feedback from the phone 4 Call this function in your code after you have created a connection to your cell phone HINT These string operators can be useful strlen strcat and strcpy Look up on the internet on how to use them HINT 2 The standard library function itoa can be used to convert integer to string HINT 3 Include the necessary libraries Explanation user_ input u_char user_input FILE stream u_char buffer u_char count This function reads user input from stream It stops after a newline or count 1 characters have been read The argument stream can for example be the terminal i e stdout The parameter buffer is a pointer to a buffer where the input is received It has to be allocated with enough space The input is always null terminated The function returns the length of the input string in the buffer Optional Exercise 8 6 Create a simple user interface to input the message and recipient s phone number and if desired the Bluetooth address of the sending phone through the terminal Use the user_input function 67 Chapter 9 The Chipcon Radio 9 1 Introduction The BTnode features a Chipcon CC1000 radio module the same radio that is used in the popular MICA mote platform allowing those two platforms to communicate over a common radio channel In contrast to the Bluetooth radio module which was cov
9. NOFORK never returns After the usual initializations for an explanation of init_stdout see page 29 the terminal thread is initialized with btn terminal init the first argument links it with the UART of the standard output stream the second argument defines the prompt of the command line you may use any string you like Finally the command btn terminal run BTN TERMINAL NOFORK 0 starts the terminal The function never returns unless you use BTN TERMINAL FORK as the first parameter in which case the terminal is started in a separate thread We will explain threads in chapter Using a terminal program such as minicom or Hyperterm we can now interact with our BTnode program However except for a small message and a prompt there isn t yet much we can do Fortunately BTnut already comes with a few commands that we can readily make available in our terminal Explanation Predefined Terminal Commands The BTnut OS offers sets of predefined terminal commands To use them they have to be registered Two of these sets with the corresponding header file and the register function are given below Similar command sets also exist for the bluetooth radio bt and the debug logger log include lt terminal btn cmds h gt btn_cmds_register_cmds include lt terminal nut cmds h gt nut_cmds_register_cmds The register commands have to be called after btn_terminal_init and before btn_terminal_run For examp
10. Nut OS and therefore also BTnut employ cooperative multithreading This means that in order to execute two or more threads at the same time each process needs to periodically give up control to the OS scheduler This will be described in more detail in section 3 below right after we explain how to create our own threads in section 5 2 Sections 5 4 and 5 5 finally introduce the concepts of mutexes and events respectively which are means of coordination and communication between threads 5 2 Creating Threads Using BTnut we can easily define and run our own threads First we look at how threads are defined 34 CHAPTER 5 PROGRAMMING WITH THREADS Explanation Creating Threads Threads are functions As mentioned earlier the main routine itself is also a thread which is started automatically after startup fortunately this is completely transparent to the programmer thanks to Nut OS Additional threads have to be declared using the THREAD macro An example defining the thread my thread is shown below include lt sys thread h gt THREAD my_thread arg for do something Functions that are used as threads are supposed to never return thus to loop endlessly if you want to end a thread you will need to manually call NutThreadExit The second argument of the THREAD macro called arg here is a void pointer and can be used to pass an argument of arbitrary type to the thread when it is created note t
11. include lt hardware btn hardware h gt include lt dev irqreg h gt COMPUTE ADC values corresponding to 1 and 2 Volts If battery voltage is 1V the BAT_SENSE signal is 0 5V The reference voltage is 3 3V and corresponds to the ADC value 1024 Therefore 0 5V corresponds to an ADC value of 1024 3 3 0 5 155 battery voltage is 2V ADC value is 310 define BAT 1 VOLT 155 define BAT 2 VOLT 310 void shortpause u short duration u_short i for i 0 i lt duration i void pause u_short duration u_short i for i 0 i lt duration i shortpause Oxffff void write_led u_char value volatile u_char pointer u_char dummy pointer u_char u_short value lt lt 8 dummy pointer sbi PORTB 5 asm volatile nop cbi PORTB 5 int get_battery_volt void int result ADMUX 1 lt lt MUXO ADMUX 1 lt lt MUX1 ADCSRA 1 lt lt ADPSO 98 APPENDIX B SOLUTIONS ADCSRA 1 lt lt ADPS1 ADCSRA 1 lt lt ADPS2 ADCSRA 1 lt lt ADEN ADCSRA 1 lt lt ADSC while ADCSRA amp 1 lt lt ADSC result ADCL result ADCH lt lt 8 return result static void timer3IRQ void arg int int battery_voltage get_battery_volt if battery_voltage lt BAT_1_VOLT write_led 0x02 else if battery_voltage lt BAT_2_VOLT write led 0x04 else write_led 0x08 T Reset
12. BInode Programming An Introduction to BTnut Applications Number 1 5 Jan Beutel Philipp Blum Matthias Dyer Clemens Moser Mustafa Y cel Philipp Stadelmann Computer Engineering and Networks Laboratory ETH Zurich 8092 Zurich Switzerland beutel blum dyer moser yuecel tik ee ethz ch with contributions by Marc Langheinrich Jonas Wolf Institute for Pervasive Computing ETH Zurich 8092 Zurich Switzerland langhein wolfj inf ethz ch The BTnode Project January 22 2007 CONTENTS iii Contents 1 1 The BTnodes and the BTnut System Software 2 2e 1 2 Intended Audience 20 29 aa a a Ha ad RR oe ed 1 3 Hard and Software Requirements les 1 4 Reference Documents 1 5 Overview a u Ee RO Ee Rok mom oso d d dox EU XD RR Rd O N N HM 2 First Steps in BTnode Programming 2 1 Introductions ee aoe en a A ue 2 2 Development Tools ess aa y 3 2 ke 2 sa wars Ka SCR aa v v m an 2 21 Compilation s s s sa dad e hs sos 2 2 2 Simulation and Debugging 2 2 3 Project Management a ea i u a a aa adi k a a DO ea en 2 2 4 Embedded Target 2 2 5 Documentation Tools 2 3 Notes on the B Tnode Hardware Architecture 2 4 B Inut Syste
13. count printf main enters endless loop n pause 12 for NutThreadYield return 0 Solution 6 6 printf Thread s has received event no d n runningThread gt td_name count include lt io h gt include lt stdio h gt include lt dev usartavr h gt include lt sys thread h gt include lt sys timer h gt include lt sys tracer h gt include lt hardware btn hardware h gt include lt led btn led h gt include lt terminal btn terminal h gt int init_stdout void 112 APPENDIX B SOLUTIONS u long baud 57600 sbi PORTD 2 NutRegisterDevice amp APP_UART 0 0 freopen APP_UART dev_name r stdout _ioctl _fileno stdout UART SETSPEED amp baud return 1 THREAD ledthread arg for btn led clear LED1 btn led set LEDO NutSleep 500 btn led clear LEDO btn led set LED1 NutSleep 500 int main void hardware init btn hardware init btn led init 0 init stdout NutThreadCreate LedThr ledthread 0 192 btn terminal init stdout bt cmd btnode btn terminal register cmd trace NutTraceTerminal btn terminal run BTN TERMINAL NOFORK 0 return 0 Solution 7 1 The Bluetooth device address can be found on a label attached to the B Inode and consists of 6 bytes e g 00 04 3F 00 00 4B Solution 7 2 Struct bt hci pkt cmd pkt pkt type 0x01 HCI command packet pkt payload 0 0x
14. e External data cache 3x60 kByte low power SRAM e Four LED s for easy debugging e In system programming through serial ISP programmer JTAG or resident bootloader Bluetooth Radio Zeevo ZV4002 Bluetooth radio running HCI firmware It is connected to the AT mega128l through a UART interface Low Power Radio Chipcon CC1000 radio operating at 868 MHz Other operating frequencies can be used according to the CC1000 documentation 433 915 MHz Both an integrated monopole antenna an external wire and an external coaxial connector MMCX type are possible though assembly options The default assembly variant is the internal monopole antenna and operation in the 868 MHz ISM band Power Supply The standard power supply are 2 cell AA batteries The common range for these is 2 3 V DC when either primary or rechargeable batteries are used The primary boost converter has a nominal input range of 0 5 3 3 V DC Alternatively 3 6 5 V can be supplied through the VDC IN pin available on the external connectors J1 and J2 e Primary supply Linear Technologies LTC3429 600mA max input 0 5 3 3 V to 3 3 V e Alternate supply Linear Technologies LT1962 300mA max input 3 6 5 0 V to 3 3 V e Switchable power groups for IO Bluetooth and LPR radio e Battery charge indicator e On Off switch for the primary power supply A detailed hardware reference is available though the BTnode website see section 1 4 8 CHAPTER 2 FIRST STEPS IN BTNO
15. u_short value lt lt 8 dummy pointer sbi PORTB 5 asm volatile nop cbi PORTB 5 int get_battery_volt void int result ADMUX 1 MUXO ADMUX 1 lt lt MUX1 ADCSRA 1 lt lt ADPSO 101 ADCSRA 1 lt lt ADPS1 ADCSRA 1 lt lt ADPS2 ADCSRA 1 lt lt ADEN ADCSRA 1 lt lt ADSC while ADCSRA amp 1 lt lt ADSC result ADCL result ADCH lt lt 8 return result static void timer3IRQ void 1 battery voltage get battery volt if battery voltage lt BAT 1 VOLT write led 0x02 else if battery voltage lt BAT 2 VOLT write led 0x04 1 write led 0x08 Reset the counter to non zero value see expl in main routine TCNT3H 0x21 TCNT3L 0x64 adc_done 1 int init stdout void u_long baud 57600 sbi PORTD 2 NutRegisterDevice amp APP_UART 0 0 freopen APP UART dev name r stdout _ioctl _fileno stdout UART SETSPEED amp baud return 1 int main void 1 init stdout printf Hello world Wn DDRB 1 DDB5 NutRegisterIrqHandler amp sig_OVERFLOW3 timer3IRQ 0 16 bit timer without prescaler clock frequency 7 3MHz gt overflows once every Oxffff 1 7 3E6 s 9ms For an overflow every 2s prescaler should be 2s 9ms 223 The closest value is 256 see table on page 135 This gives an overflow every 2 3s This could be adjusted by setting the cou
16. void write_led u_char value int volatile u char pointer u char dummy pointer u_char u_short value lt lt 8 dummy pointer Sbi PORTB 5 asm volatile nop cbi PORTB 5 Eget battery volt void int result ADMUX 1 MUXO ADMUX 1 lt lt MUX1 ADCSRA 1 lt lt ADPSO ADCSRA 1 lt lt ADPS1 ADCSRA 1 lt lt ADPS2 ADCSRA 1 lt lt ADEN ADCSRA 1 lt lt ADSC while ADCSRA amp 1 lt lt ADSC result ADCL result ADCH lt lt 8 return result static void timer3IRQ void arg int int battery_voltage get_battery_volt if battery voltage BAT_1_VOLT write led 0x02 else if battery_voltage lt BAT_2_VOLT write_led 0x04 else write_led 0x08 main void int toggle 0 DDRB 1 lt lt DDB5 NutRegisterIrqHandler amp sig_OUTPUT_COMPARE3A timer3IRQ 0 16 bit timer without prescaler clock frequency 7 3MHz gt overflows once every Oxffff 1 7 3E6 s 9ms For an overflow every 2s prescaler should be 2s 9ms 223 The closest value is 256 see table on page 135 This gives an overflow every 2 3s TCCR3B 1 lt lt CS32 To get an interrupt every 2s the interrupt should be triggered when the counter reaches 2 2 3 0xffff Oxde9a OCR3AH Oxde OCR3AL 0x9a Enable this interrupt ETIMSK 1 lt lt 0 100 APPENDIX B SOLUTIONS
17. 0 0 freopen APP_UART dev_name r stdout _ioctl _fileno stdout UART SETSPEED amp baud return 1 void EnterCritical void temp sreg SREG cliO void ExitCritical void i int SREG temp sreg an explicit sei is not necessary since the I flag is already set if it had been before the previous EnterCritical main void int battery voltage volt init_stdout printf Hello world n DDRB 1 lt lt DDB5 NutRegisterIrqHandler amp sig_OVERFLOW3 timer3IRQ 0 16 bit timer without prescaler clock frequency 7 3MHz gt overflows once every Oxffff 1 7 3E6 s 9ms For an overflow every 2s prescaler should be 2s 9ms 223 The closest value is 256 see table on page 135 This gives an overflow every 2 3s This could be adjusted by setting the counter value to 0 3 2 3 0xfffff 0x2164 after every overflow thus at the end of the timer interrupt routine TCCR3B 1 lt lt CS32 ETIMSK 1 lt lt TOIE3 EnterCritical while 1 while adc done 0 adc done is shared ExitCritical pause is not necessary EnterCritical battery_voltage_volt 3300 long battery_voltage 512 battery_voltage is shared printf Battery voltage is d millivolts n battery_voltage_volt battery voltage is shared adc_done 0 adc_done is shared I ExitCritical return 0 104 APPENDIX B SOLUTIONS Solution 3 12 In line 7 the valu
18. Specification of the Bluetooth System v 1 2 November 2003 J L Hennessy and D A Patterson Computer organization and design The hardware software interface Morgan Kaufmann Publishers San Francisco CA 2nd edition 1997 J L Hill and D Culler Mica A wireless platform for deeply embedded networks IEEE Micro 22 6 12 24 November 2002 Microchip Technology Inc T C74 Tiny Serial Digital Thermal Sensor 2002 Ltd Murata Manufacturing Co 7BB 12 9 Piezoelectric Diaphragm 2001 Nokia Support Guide for the Nokia Phones and AT Commands May 2002 J Polastre J Hill and D Culler Versatile low power media access for wireless sensor networks In Proc 2nd ACM Conf Embedded Networked Sensor Systems SenSys 2004 pages 95 107 ACM Press New York 2004 Texas Advanced Optoelectronic Solutions TSL205R Light to Voltage Optical Sensor 2001 Sony Ericsson Developers Guidelines AT Commands August 2005 Matsushita Electric Works AMN1 Napion Digital Passive IR Motion Sensor 2001
19. avrdude 66182 bytes of flash written avrdude safemode Fuses OK avrdude done Thank you Solution 2 15 avrdude AVR device initialized and ready to accept instructions Reading JHHHHHHEHBHBHHHBHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHE 100 0 02s avrdude Device signature 0x1e9702 avrdude NOTE FLASH memory has been specified an erase cycle will be performed To disable this feature specify the D option avrdude erasing chip avrdude reading input file uart echo btnode3 hex avrdude writing flash 13410 bytes Writing fHHHHHHHHHBEHHHHBHHHHHHHHHHHHHHHHHHHHHHHBHHHHHHHHHHHE 100 2 95s avrdude 13410 bytes of flash written avrdude verifying flash memory against uart echo btnode3 hex avrdude load data flash data from input file uart echo btnode3 hex avrdude input file uart echo btnode3 hex contains 13410 bytes avrdude reading on chip flash data Reading JHHHHHEBHBHHBHHHBHHHHHHBHHHHHHHHHHHHHHHHHHHHHHHHHHHHE 100 1 48s avrdude verifying avrdude 13410 bytes of flash verified avrdude safemode Fuses OK avrdude done Thank you Solution 2 16 make btnode3 echo define PROGRAM VERSION 20060405 1501 gt program version tmp mv f program version tmp program version h avr gcc c mmcu atmegai28 0s Wall Werror Wstrict prototypes Wa ahlms bt cmd btnode3 1st D HARVARD ARCH D__BTNODE3__ DUSE USARTO DUARTO_READMULTIBYTE DUARTO_NO_SW_FLOWCONTROL DUSE USART1 DUART1_READMULTIBYTE DUAR
20. return pkt If you now define the packet u_char acl_pkt 120 a register the receive function as a callback bt_hci_register_acl_cb stack receive struct bt_hci_pkt_acl acl_pkt NULL messages sent to your BTnode will be displayed automatically on the terminal Exercise 7 7 Test your transmit function by sending a short message to a SUPERVISOR node that uses a preloaded application Use channel 65 for sending this message If you have implemented everything corretly so far you will receive an acknowledgment from the SUPERVISOR node immediately Optional Exercise 7 8 Check if some of your neighbors have already finished exercise 7 7 Try to com municate with another group doing this tutorial Optionally try to combine commands from bt cmd such as name rname role roleset with transmit to get status information from other nodes 56 CHAPTER 7 COMMUNICATION USING BLUETOOTH 57 Chapter 8 Interfacing to Handheld Devices 8 1 Introduction In addition to the regular BTnode hardware a cellular phone with a Bluetooth interface is required for successful completion of this tutorial Figure shows an overview of the Bluetooth protocol stack On top of the Host Controller Interface HCI and the Logical Link Control and Adaptation Layer Protocol L2CAP the Bluetooth stack provides the RFCOMM protocol which emulates a serial port connection Over such a RFCOMM connection basic Attention Commands AT Commands can be s
21. v Furthermore we will test avrdude v optional also uisp version that we will later use to upload code to the ATmega128l 2 5 FIRST STEPS IN BTNODE PROGRAMMING USING THE AVR GCC TOOLCHAIN 13 AVRStudio 1 Project Yew Tools Debug Heb EDGHOgO smBe sccocmmeg 4 IAN HOOVER 3 race Disabled 15 x 6 ee Ne oto Workspace x Program Fuses LockBis Advanced Board Auto Device ATmegal28 v Erase Device Programming mode ISP IV Erase Device Before Progamming C Paralel Hich Voltage Sers 7 Verity Device After Programming Flash Current Simulator Emulator FLASH Memory Input HEX File C eclipse ESworkspace btnut_snap app bt Program Verity Read p EEPROM Use Current Simulator Emulator EEPROM Memory Input HEX File sd Program Verity Read Setting device parameters serial programming mode OK Entering programming mode Reading fuses OFF Ox008E OK Leaving programming mode OK Loaded plugin STKSO0 x I NBI Messages FITTE P CAP NUM SCRL Figure 2 5 AVR Studio offers a graphical frontend to programming simulation and project management functions Optional Exercise 2 11 To see specific hints and help om the toolchain execute the tools with the help parameter from the command line or the man
22. verbose debug of all hei information i GS uart echo 94 bt hci debug uart 1 8 25 uart suart 95 Makefile 36 Start the stack and let the initialization begin si readme txt 1 af iB doc 8 05 indude Problems Properties Synchronize cvs Resource History Search Progress a g 0 0 ma AM C Bulld btnut snap make k all n um avr gec c mmcu atmegal28 Os Wall Werror Wstrict prototypes Wa ahlms bt cmd btnode3 lst Makedefs D__HARVARD_ARCH D__BTNODE3 1 include bt cmd c o bt cmd btnode3 o 2 Makerules avr gcc bt cmd btnode3 0 lib btnode3 nutinit o L lib btnode3 mmcu atmegal28 Wl E REUS defsym main 0 Map bt cmd btnode3 map cref L lib btnode3 Inutos Inutdev lbt Ihardware m EASE leepromdb lsuart lled lcc lhardware lterminal Inutert Inutdev Inutos lbt lm Inutert gt lled lhardware lnutdev o bt cmd btnode3 elf avr size bt cmd btnode3 elf text bss dec hex filename 53626 876 182 54684 d59c bt cmd btnode3 elf avr objcopy O ihex bt cmd btnode3 elf bt cmd btnode3 hex rm bt cmd btnode3 elf zl i Figure 2 4 The C C perspective with the C C Projects view on the left a file editor in the top console view in the bottom middle and the Make Target view open on the right Exercise 2 4 Open the BT nut System Software Reference an online version of the BTnut API is available on http www btnode ethz ch or locally in doc html in a w
23. 1 also starts a separate LED thread The LED thread displays dynamic patterns on the LEDs typically to indicate that the program is still running heartbeat Its pattern can be set with a single command i e using btn led add pattern or btn led heartbeat See the BTnut system software reference for a detailed description of these commands By default the LED thread starts to blink with the blue LED after initialization Note that even when the heartbeat is active we still can switch on and off LEDs individually using the commands btn led set and btn led clear The LED thread will remember the pattern it was showing before LEDs are switched on manually and restart displaying the pattern after all these LEDs are cleared again manually Exercise 5 3 Write a program with a main routine and an additional thread Both threads repeatedly write a message to the terminal and then yield using NutThreadYield What do you observe HINT you can freeze terminal output in minicom using Ctrl A Do you have an explanation HINT Writing to the terminal is done with the speed of the UART e g 57600 bits per second which is slow in comparison to the speed of the CPU HINT No 2 printf does not directly write to the UART instead it writes to a buffer with a limited capacity default is 64 characters Explanation Thread Priorities and States Each thread in BTnut has a priority a value from 0 254 The idle thread has the lowest
24. 2x 2x 2x addr 5 addr 4 addr 3 addr 2 addr 1 addr 0 F print the number of found devices and their addresses void print_inq_result struct bt_hci_cmd_response wcmd int i printf Devices li n wcmd response if wcmd response lt 0 wcmd response 0 else printf Device bt addr in for i 0 i wcmd response i printf Ad 1 print bt addr struct bt_hci_inquiry_result wcmd ptr i bdaddr printf Nn void inquiry char arg J RRR ae ak ak ak ak ak ak ak packet struct bt hci pkt cmd pkt pkt type HCI COMMAND DATA PACKET pkt payload 0 HCI OCF LC INQUIRY pkt payload 1 HCI OGF LINK CONTROL 2 cmd length 5 bytes pkt payload 2 0x05 General Inquiry Access Code GIAC pkt payload 3 0x33 pkt payload 4 0x8b pkt payload 5 0x9e waiting time for the inquiry to complete gt 5 1 28 s 6 4 s pkt payload 6 0x05 maximum number of responding devices pkt payload 7 0x05 prepare and register cmd_response structure Struct bt hci cmd response wcmd array for the storage of the answers of max 10 devices struct bt hci inquiry result inquiry result 10 initialize the cmd response structure wemd ogfocf HCI_OCF_LC_INQUIRY lt lt 8 HCI OGF LINK CONTROL 2 wcmd cmd
25. ADVANCED TOPICS 73 printf Setting RF power to u n num cc1000 set RF power num Exercise 9 7 Write a program to measure the transmission distance for different power levels i e find out how far away a signal sent with tranmission power 1 2 or 3 can be still received or how much power is necessary to contact a node at say 5 meter distance or in another room Optional Exercise 9 8 Change your program from ez so that PING TYPE packets include as payload the sender s current power level initially set to its maximum of 255 Upon receiving such a packet the receiver should print this information to STDOUT and acknowledge it with PONG TYPE packet Receiving a PONG TYPE packet should lower sender s transmission power before sending out another PING TYPE packet Take two nodes and measure various distances that certaim power levels can achieve Optional Exercise 9 9 Extend your program from ez 9 7 so that it will build a neighborhood table of the closest n neighbors and their power level distances Optional Exercise 9 10 Implement a multi hop flooding protocol on the BTnodes You will need to set the power level to a reasonably small number e g 2 8 All packets will be sent to the broadcast address and contain a packet ID that allows nodes to detect packets they already sent in order to avoide reduplicating packets Test your protocol by flooding your network with a certain LED pattern i e u
26. BTnode platform so it should also be beneficial to the occassional computer scientist not versed in all things electrical Each chapter comes with a set of exercises that are supposed to get you accustomed to basic everyday tasks of an embedded engineer The order in which the exercises are performed is not of crucial importance and whole chapters can be left out to suit the individual needs e g computer scientists might want to skip those concerning hardware issues However we suggest that you perform the exercises in the order given to minimize unforeseen complications 1 3 Hard and Software Requirements Figure 1 2 The BTnode development kit The minimal set of tools consists of the three items on the very right a BTnode a USB programming board and a USB cable Additionally some exercises require the use of an ISP programmer a serial cable and a 15 Pin Molex breakout cable left half To be able to do all of the practical exercises in this tutorial you will need a complete BTnode developer kit see Figure 1 2 consisting of a BTnode rev3 a usbprog USB programming adapter an ISP programmer we suggest the Atmel ATAVRISP or alternatively the ATAVRISP MK2 programmer serial and USB cables a 15 Pin Molex breakout cable and the software documentation and tools contained on the BTnode CDROM 1 4 REFERENCE DOCUMENTS 3 see Figure L 3 However a number of exercises can also be performed with a minimal subset of these too
27. BTnut the above ADC functions are encapsulated in the dev adc h library All of the above mentioned functions disabling enabling and configuring the ADC as well as reading out converted values can be achieved with a set of dedicated functions and corresponding constants thus increasing code legibility and portability However the adc h library is unable to cope with concurrent use making it practically unusable This is because other threads might concurrently use the ADC for other purposes e g to measure the current battery level thus reconfiguring the ADC repeatedly In order to get reliable measurements it is imperative to assert that the current ADC configuration still matches the desired one or change it if otherwise The dev adc2 h library offers the adc2 init and adc2 read functions which are much more robust than their dev adc h counterparts and also support configuration validation 10 3 READING SENSOR DATA 81 Explanation Using ADC in BTnut The functions adc2_init and adc2_read are defined in the library dev adc2 h In contrast to the regular dev adc h library these functions also support ADC context switches i e the concurrent use of the ADC by other threads include lt dev adc2 h gt static u_short my_adc_handle saves ADC context int main void my adc handle adc2 init ADC2 MODE SINGLE CONVERSION ADC2 PRESCALE DIV2 ADC2 CHANNELO ADC2 REF AREF for f val adc2_read my_adc_handle
28. ICE50 with the ones of a JTAG debugger JTAGICE 2 What is on chip debugging OCD Which hardware is required for OCD on the BTnode 3 What happens with the peripheral components of the uC UART Timers A D Converter when you enter stop mode for source level debugging e g when a breakpoint is hit Optional Exercise 6 2 Consider following table Which tool s is are most appropriate in your opinion for the given problems Sometimes all tools can be applied in order find and fiz a bug Some with more others with less effort Justify your answer Problem Tool Simulator Reason JTAGICE printf An algorithm that operates from memory to memory does not behave as expected The uC communicates over one of its hardware UART with the Bluetooth module In general the uC sends a command sequence and parses the reply from the module The implementation of this protocol on the LLC is erroneous and needs debugging You are implementing a network stack A series of function is called for each network layer to process an incoming packet In your current implementation when a packet is received the freezes somewhere in the processing You want to find out where 6 4 AVR SIMULATION 43 6 4 AVR Simulation In this section you will learn how to use AVR simulation for prototyping and source level debugging We introduce two simulators simulavr and the AVR Studio Simulator Unfortunately
29. O components for better insight JTAG debuggers directly connect to the real chip instead of replacing it ICEs and JTAG debuggers can be used for source level debugging 1 ten secrets of embedded debugging http www embedded com showArticle jhtml articleID 47208538 42 CHAPTER 6 EMBEDDED DEBUGGING Explanation Simple printf statements This is perhaps the most flexible and primitive tool Printing out variable values and function entry exit points allows you to discover how your program is operating Unfortunately printf is both clumsy to use requiring code changes and recompiling and quite intrusive because it greatly slows execution Explanation Operating system monitors Operating system monitors display events such as task switches semaphore activity and interrupts Others Profilers memory testers execution tracers coverage testers 6 3 Debugging Techniques for the B Tnode Following tools can be used to debug an AVR microcontroller Some techniques require additional special hard and software Technique Hardware Software 1 Simulator AVRStudio AVaRICE GDB SimulAVR GDB 2 ICE ICE40 ICE50 AVRStudio 3 JTAG debugger JTAGICE mkII AVRStudio AVR insight 4 printf UART Terminal 5 OS monitor UART Nut OS Tracer Terminal Optional Exercise 6 1 Open the AVRStudio and consult the AVR Studio Tools and User Guide 1 Compare the features and limitations of an Emulator
30. a packet type We can use the new_ccc_packet function to obtain a pointer to an empty packet struct with memory allocated up to the given size PACKET_SIZE in our example code above However we still need to explicit specify the actual length of each packet that gets sent by setting the length attribute accordingly Exercise 9 2 Lookup the source code of the ccc_send in the BTnut sources How is sending data im plemented Why is ccc_send not doing the actual data transmission Lookup the corresponding _send function in bmac c and explain Explanation Addressing in B MAC For each packet sent using ccc_send a destination address must be given The B MAC implementation uses a two tiered 16 bit address structure composed of 21 i e 2048 clusters with 2 1 i e 31 individual addresses each A reserved broadcast address BROADCAST_ADDR OxFFFF can be used to address all nodes in all clusters Each cluster except for cluster 2047 also has a multicast address which is simply the highest address in the cluster Table 9 1 gives an overview In practice the cluster address of a particular node does not matter much As long as nodes are in range of each other nodes from any cluster can send and receive data from nodes from any other cluster Clusters are simply a means to form subgroups of nodes that can easily communicate among each other using a cluster specific broadcast called a cluster multicast Special care mu
31. avr io h 10 2 SENSOR TYPES TT ADC4 TCK ADC5 TMS ADC6 TDO ADC7 TDI 8588 seq 2552333 eee OOUoc uosooroQgordg gt SZE LLC LU UL UL 2 lt lt lt zo lt aaaaaanaa os a DLLELDLELELELELDLELELELDLEL EL z d 599859g25550295g00oo0S9 PENL 48 1 AD3 RXDO PDI PEO 2 47 PA4 AD4 TXDO PDO PE1 46 1 PAS ADS XCKO AINO PE2 C 4 45 1 PA6 AD6 OC3A AIN1 O 5 44 B AD7 OC3B INTA PE4 C 6 43 1 PG2 ALE 5 PES O7 42 A15 T3 INT6 PES C 8 41 1 PC6 A14 ICP3 INT7 PE7 C 9 40 D PC5 13 SS PBo 10 39 O PC4 A12 SCK PB1 11 38 1 A11 MOSI PB2 O 12 37 O PC2 A10 MISO PBS C 13 36 1 PC1 A9 PB4 14 35 O PCO A8 5 O 15 34 1 PG1 RD OCIB PBeC 18 5 5 5 ue ew or ooo 9 HPSXWR TETSRSSRSQSSSNSQS 5S anoolhog23285888885 ficos zzotccchbca oN Sle KXISTNRTErN BEEEQYLEE 227272006 0 Sge ager 8 3522 8 SBE Figure 10 2 Ports of the ATmegal28L I Exercise 10 1 Use the AT mega128L user manual 1 to find out which pins have the alternate function of serving as the data SDA and clock SCL line of the so called two wire interface TWI Find out what bit needs to be set in which hardware register in order to enable TWI support in the ATmega128L Exercise 10 2 Locate the schematic for the B Tsense sensor board at www btnode ethz ch search under Hardware Re
32. both of them are quite limited i e they only simulate a subset of the AVR peripherals timers etc As a consequence applications that use Nut OS can not be simulated The simulator usually breaks in one of the timer interrupt routines Exercise 6 3 Simulavr AVR Insight In this exercise you will learn how to start simulavr and how to connect the AVR Insight debugger to it T 6 Create a new C file simpleio c with the following code include lt io h gt void delay void int i for i 0 i lt 1000 i int main void DDRF _BV 0 for PORTF _BV 0 delay PORTF amp _BV 0 delay Compile the file manually with the debug symbols option g avr gcc mmcu atmega128 g I usr pack btnode 1 0 mo avr include avr simpleio c o simpleio elf Start AVR Insight avr insight amp Start simulavr as a gdb server simulavr g d atmega128 The simulator should print out something like Waiting on port 1212 for gdb client to connect In order to connect Insight with the simulator open the gdb console View Console and enter fol lowing commands file simpleio elf target remote localhost 1212 load break main continue Congratulations now you can step through your code set breakpoints and watches Optional Exercise 6 4 AVR Studio Simulator 1 2 AVR Studio needs a different debug format Compile the code from the last exercise with gdwarf 2 Open AVRStudio and op
33. btsense_init BTSENSE_REVISION_1_1 u_short light btsense_sample_light printf Light Level d n light u_char motion btsense sample motion printf Motion Level d n motion u_char temp int err if err btsense sample temp amp temp 1 TWI error printf TWI Error d n err else printf Temperature Level d n temp make a beep btsense_sound 440 NutSleep 1000 btsense_sound 0 for NutSleep 5000 TCNTn OCn COMn1 0 2 OCn l 1 0 3 Period 2 6667 Figure 10 4 Waveform generation in Fast PWM mode I Periods are constant signal width is according to TOP value horizontal bars In addition to the btsense library a number of helper functions are available via adc2 adc2 h see the source code for details Exercise 10 10 Write a program that comverts the light levels detected by the light sensor into a corre sponding LED meter i e the brighter it is the more LEDs light up 10 4 THE BTSENSE LIBRARY 87 TCNTn OCn 1 0 2 OCn COMn1 0 3 Period ELM Figure 10 5 Waveform generation in Phase Correct PWM mode I Notice how signals are centered within constant periods Optional Exercise 10 11 Extend the program from ex 10 10 to also sound the buzzer at different frequency levels according to the detected light level Exercise 10 12 Write a pro
34. bytes are set by the bt_hci_send_acl_pkt function hci acl pkt O type nei_acl_pkt 1 con handle hci_acl_pkt 2 con handle flags nci_acl_pkt 3 flags data length hci acl pkt 4 data length hci acl pkt 5 u char 20 amp OxFF 116 APPENDIX B SOLUTIONS hci acl pkt 6 u char 20 gt gt 8 amp OxFF hci_acl_pkt 7 u_char channel amp OxFF hci_acl_pkt 8 u_char channel gt gt 8 amp OxFF attach the string message for i 0 i lt 18 i hci_acl_pkt 9 i message i and send the packet bt hci send acl pkt stack handle 2 0 24 struct bt_hci_pkt_acl hci_acl_pkt printf Message s sent with handle channel Ad Wn message handle channel struct bt_hci_pkt_acl receive void arg struct bt_hci_pkt_acl pkt bt hci con handle t con handle u char pb flag u char bc flag u short len u long t arrive f u char 12cap_hdr pkt gt payload u_char 12cap_data u_short chan_id chan_id 12cap_hdr 2 12cap_hdr 3 lt lt 8 12cap_data amp 12cap_hdr 4 printf message received on channel Ad s n chan id 12cap_data return pkt t main function that initializes the hardware led terminal bluetooth and acl communication stack and registers some predefined commands Use tab tab to see the registered commands once the program is running int main void u_char acl_pkt 120 serial baud rate u_long baud 57600 u_long cpu_c
35. considerably reducing the idle power consumption of the device BTnodes run an embedded systems OS from the open source domain called Nut OS Nut OS is designed for the Atmel ATmegal28 microcontroller which is used on the BTnodes and intentionally kept very simple According to the Nut OS description it features e Non preemptive cooperative multi threading e Events e Periodic and one shot timers e Dynamic heap memory allocation e Interrupt driven streaming I O 2 CHAPTER 1 INTRODUCTION In order to use Nut OS on the BTnodes a set of BTnode specific drivers have been added and in particular a Bluetooth stack for its on board Bluetooth radio These three pieces form together the BTnut system software or short BTnut In this tutorial we will learn how to use the BTnut system software to deploy sensor node applications on the BTnode wireless sensor node platform 1 2 Intended Audience This tutorial originated in the Embedded Systems lecture a graduate course taught at the Department of Information Technology and Electrical Engineering ETH Zurich and a graduate course on Wireless Sensor Network taught at the Department of Computer Science ETH Zurich It requires basic knowledge of C programming and embedded systems and should give an overview of the capabilities of networked embedded systems and their key properties However apart from its usage in the lecture this tutorial provides a basic introduction to programming on the
36. example bt cmd bt cmd c date 2004 06 18 author Jan Beutel lt j beutel ieee org gt Example application to show the use of the bt stack and the simple but author Martin Hinz lt btnode hinz ch gt powerful terminal interface include lt stdio h gt include lt dev usartavr h gt include lt sys heap h gt include lt sys timer h gt include lt hardware btn hardware h gt include lt bt bt_hci_cmds h gt include lt terminal btn terminal h gt include lt terminal btn cmds h gt include lt terminal bt cmds h gt include lt terminal nut cmds h gt include lt terminal log cmds h gt include lt led btn led h gt include lt debug logging h gt include program_version h define CVS_VERSION Id ex7 6 listing c v 1 2 2007 01 17 19 21 30 yuecelm Exp struct btstack stack extern u_char _bt_hci_debug_uart sending a text message on a certain channel with a certain connection handle void transmit char arg int handle channel i u_char message 20 set empty message for i 0 i lt 19 i message i dont separate single words in message with spaces BUT leave space after end of message otherwise bluetooth module may be re booted sscanf arg u u s amp handle amp channel message define a packet 5 bytes for hci packet header 4 bytes for L2CAP packet header and 20 bytes payload u_char hci_acl_pkt 29 the following
37. handle BT HCI HANDLE INVALID wcmd response 0 wcmd ptr amp inquiry result wcmd block 0 register the wcmd in the WaitQueue of the running stack bt hci setWaitQueue stack amp wcmd send packet wait and readout the results bt hci send pkt stack u_char amp pkt printf Starting inquiry n NutEventWait amp wcmd block NUT_WAIT_INFINITE printf Inquiry done n print_ing_result int main void btn hardware init btn led init 0 init stdout O bluetooth module on takes a while btn hardware bt on O Start the stack and let the initialization begin 114 APPENDIX B SOLUTIONS Stack bt hci init amp BT UART btn terminal init stdout es200X btn terminal register cmd inquiry inquiry btn terminal register cmd trace NutTraceTerminal btn terminal run BTN TERMINAL NOFORK 0 return 0 J Solution 7 4 You can clearly identify a CommandStatusEvent several InquiryResultEvents as well as a final InquiryCompleteEvent Solution 7 6 sending a string message within an acl packet Copyright C 2000 2006 by ETH Zurich Redistribution and use in source and binary forms with or without modification are permitted provided that the following conditions are met 1 Redistributions of source code must retain the above copyright notice this list of conditions and the following disclaim
38. known communication protocols to send and receive text from a remote computer See the online documentation at http www btnode ethz ch for information on how to setup a terminal program under Linux e g minicom or Windows e g Hyperterm Explanation Setting up the terminal The printf function writes a formatted string to the standard output stream But before using printf we have to setup the standard output stream explicitly i e we have to define that we want to link the standard output to the UART1 This can be done using a routine like to following include lt stdio h gt freopen includes lt io h gt for _ioctl include lt dev usartavr h gt NutRegisterDevice APP_UART UART_SETSPEED void init_stdout void 1 u long baud 57600 NutRegisterDevice amp APP_UART O 0 freopen APP_UART dev_name r stdout r read write ioctl fileno stdout UART_SETSPEED amp baud Once we have established a terminal connection we can write text to it using the well known printf function which is provided for the ATmegal28 platform in avr libc Most standard conversion strings e g for signed integers and special characters e g Nn can be used but not all For example the float conversion is not implemented as the ATmegal28 does not support floating point operations HINT Exit the terminal program again before trying to upload a new program to the BTnode otherwise the bootloader s up
39. make sure that a lost packet will not put the two nodes permanently out of synch 9 3 3 Measuring Signal Strength The CC1000 additionally offers access to RSSI Receive Signal Strength Indication information However as this data is available only in analog form we will need to use on of the available ADCs digital analog converter on the Atmegal28 in order to obtain a digital readout Access and usage of the ADCs is covered in the sensor chapter of this tutorial see chapter 10 The many layers between our main program and the BTnut CC1000 modules further complicate matters by the time one of our packet handlers gets called packet reception has already finished so reading out RSSI data at this point will most likely only measure the channel s background noise Even if noise levels are all you want measuring RSSI in your own program will most certainly interfere with B MAC s CCA routines requiring careful coordination of ADC registers in order not to mix up different RSSI readings Optional Exercise 9 13 Where would we need to measure RSSI in order to obtain the signal strength with which a particular packet was received Look trough the three modules ccc c bmac c and cc1000 c and speculate on the best place to add RSSI measurements to a data packets struct 8B MAC s clear channel assignment CCA feature actually requires measuring the current noise level on the channel which is implemented by averaging a number of RSSI measurem
40. net e A nice avr gcc tutorial in german http www mikrocontroller net wiki AVR GCC Tutorial e Bluetooth Special Interest Group all about the standardization applications and reference documents http www bluetooth org 4 CHAPTER 1 INTRODUCTION e Technical BTnode BTnut support For technical questions concerning BTnut and the BTnode platform please inquire to the mailing list mailto btnode development list ee ethz ch 1 5 Tutorial Overview Chapter B First Steps in BTnode Programming gives a basic introduction of development tools software structure and documentation sources necessary for development on the BTnode platform Here we learn how to program an Atmel AVR microcontroller using In System Programming compile our first program use a build system to automate compilation steps and manage software projects using eclipse and CVS The chapter 3 Device Level Programming introduces simple microcontroller programming and register based input output as well as interrupts In chapter H T he BTnut Operating System we introduce higher level concepts of the BTnut operating system Application structure as well as the terminal library timers and memory management are discussed Threads are discussed in a separate chapter Programming with Threads chapter 5 The chapter 6 Embedded Debugging is devoted to different techniques for the debugging and profiling of larger applications where bugs are i
41. possible priority 254 while main as well as all manually created threads have a default priority of 64 Priorities become important if several threads are competing for control Each thread can be in three different states RUNNING READY or SLEEPING While only one thread can be RUNNING at any moment in time this is managed by the BTnut OS several can either be READY or SLEEPING A sleeping process has ceded control either by calling NutSleep time and is woken up by the OS after at least time milliseconds have passed or is waiting for an event e g an incoming radio signal or a message from another thread more about this in section below Once the running thread cedes control using NutThreadYield its state becomes READY and BTnut transfers control to another ready to run thread the one with the highest priority If all other ready to run threads have a lower or at most equal priority control is returned to the yielding thread immediately otherwise some unknown time later Multiple threads with the same priority are executed in FIFO order Explanation Setting Thread Priorities Remember that in the BTnut OS threads have a priority in the range of 0 254 where a lower value means a higher priority The default priority is 64 You may assign the current thread a higher priority e g 20 using THREAD my thread arg NutThreadSetPriority 20 for do something Note that changing the priority of
42. received data should be put followed by the maximum number of bytes to receieve final argument indicates a timeout value which is currently not supported will be ignored It returns the number of bytes received or 1 in case of error include lt dev twif h gt void main void set TWI pins Port D Pins 0 and 1 as Input w Pull Up cbi DDRD DDDO cbi DDRD DDD1 sbi PORTD PDO sbi PORTD PD1 TwInit 0 parameter currently ignored u_char tw cmd 0x00 read temperature command u char t holds return value temperature if TwMasterTransact BTSENSE I2C TC74 amp tw cmd 1 amp t 1 0 1 printf Error while reading sensor i n TwMasterError The TwInit function simply initializes the software stack it does not configure the corresponding AT megal28L ports for us We therefor need to make sure that both of our TWI ports i e pins 0 and 1 of Port D are both configured for input using the DDRD register and have pull ups enabled using the PORTD P 3The address space can optionally be extended to 10 bit and 1008 devices 1024 16 though this is not supported on the BTnode During a high SCL level SDA levels must be stable Level changes on SDA during a high SCL indicate special START and STOP commands that a master uses to initiate or end a command 5See page 65 of the ATmegal28L user manual for an overview of I O Port configuration 10 2 SENSOR TYPES T9 Exp
43. routine ISR timer3IRQ is defined At the very begin of main timer3IRQ is registered as the service routine for the sig_OVERFLOW3 interrupt that is for the event that timer 3 overflows After registering the ISR the timer is configured The CS30 and CS32 bits of the TCCR3B register are set to configure the speed of the timer In this case the timer is incremented every 1024 clock cycles see page 135 of the manual The timer does not have to be started it is always active However the generation of interrupts when the timer overflows has to be enabled This is done by setting the TOIE3 bit of the ETIMSK register Exercise 3 5 We now will modify the previous program such that the battery power is sampled in a timer ISR Use timer 3 in such a way that the battery power is sampled approximately once every two seconds The ISR displays the sampled result on the LEDs but in contrast to the previous program it does not wait and switch on the blue LED HINT To adjust the interval of the ISR you can change the prescaler CS3x bits and or set the timer manually to a non zero value after every overflow Optional Exercise 3 6 Modify the program from the previous exercise using the clear timer on compare match CTC mode of the hardware timer which is described on page 121 and 131ff Also use the ISR to display the result of the battery power sampling using the LEDs as in the previous example In a real world program often a large number of diff
44. terminal btn terminal h gt int init_stdout void 1 u long baud 57600 sbi PORTD 2 NutRegisterDevice amp APP_UART 0 0 freopen APP UART dev name r stdout _ioctl _fileno stdout UART SETSPEED amp baud return 1 J THREAD my_thread arg IF THE variable dummy str is initialized AND USED more stack is used char dummy_str 20 int sleeptime int arg sprintf dummy_str hello world n for f printf s is alive will sleep for d seconds n runningThread gt td_name sleeptime NutSleep 1000 sleeptime void create u_char arg f static int sleeptime 1 int stacksize char name 20 int val val sscanf arg 5 4 name amp stacksize if val 2 printf Create a thread with name s and sleeptime d n name sleeptime if 0 NutThreadCreate name my_thread amp sleeptime stacksize printf FAILED n else printf SUCCESFUL n sleeptime int main void hardware init btn_hardware_init 108 APPENDIX B SOLUTIONS init_stdout btn terminal init stdout bt cmd btnode btn terminal register cmd create create nut cmds register cmdsO btn terminal run BTN TERMINAL NOFORK 0 return 0 Solution 5 12 include lt stdio h gt include lt dev usartavr h gt include lt sys thread h gt include lt sys timer h gt include lt sys tracer h gt include lt sys event h gt include lt hard
45. that is used in your program from Ex Do this by implementing the functions EnterCritical and ExitCritical Make sure that ExitCritical does not enable interrupts if they were disabled before EnterCritical Optional Exercise 3 12 Not all data access conflicts are so easily visible as the shared variable from Ex For example our implementation of the write_led function has a problem of this kind too Explain why and fix it 26 CHAPTER 3 DEVICE LEVEL PROGRAMMING 27 Chapter 4 The BTnut Operating System 4 1 Introduction In this chapter we introduce the BTnut operating system OS In comparison to the exercises of the previous chapter this has two main consequences e You do not have to read hardware schematics and spec sheets when you want to use resources since we are now able to use library functions In this chapter you will use such functions for accessing the LEDs and the terminal Also the analog to digital converter that we have used in the last chapter would be accessible through such library functions see the dev adc h header for a description There is even a function btn bat measure that does exactly what we have done manually see hardware btn bat h e Complicated programs can be divided into a set of threads Programming a single thread is often much easier than programming the whole functionality in a single program At the same time however pro gramming with multiple threads becomes more complicated
46. the battery voltage and the main routine which prints it to the terminal It is explained why this shared data has to be protected from uncoordinated concurrent access by multiple flows of control and how this can be done 24 CHAPTER 3 DEVICE LEVEL PROGRAMMING Explanation Using the terminal The ATmegal28 has also two serial interfaces so called Universal Asynchronous Receiver Transmitter UART units The UARTI is used to connect the ATmegal28 to the Bluetooth module The UARTO can be used to write ASCII text to the terminal which is a program running on the host computer Writing text to the terminal can be done using the well known printf function from the avr libc Most standard conversion strings e g d for signed integers and special characters e g Nn can be used but not all For example the float conversion is not implemented int variable 13 printf Hello world printf my lucky number is d n variable The printf function writes a formatted string to the standard output stream But before using printf we have to setup the standard output stream explicitly that is we have to define that we want to link the standard output to the UARTO This can be done using a routine like to following include lt hardware btn hardware h gt include lt stdio h gt freopen include lt io h gt _ioctl include lt dev usartavr h gt NutRegisterDevice APP_UART UART_SETSPEED void init_stdout void 1
47. them The problem is that embedded code cannot be easily executed under a debugger nor can it be easily traced because of the following circumstances e Embedded systems are resource constrained Some debugging techniques might cause too much overhead processing communication and memory Applying debugging may obscure the real problem Heisenberg effect e The embedded processor is connected to peripheral hardware components such as A D converters timers communication interfaces interrupt controllers and general purpose I O pins The embedded programm closely interacts with those components which makes it hard to trace e Embedded system often provide very limited access to the resources If all you have is four LEDs debugging will be very hard 6 2 Tools Good mechanics have many tools you can t fix a car with just a hammer Like good mechanics good programmers need to be proficient with a variety of tools Each has a place each has a Heisenberg effect each has power Explanation Simulator with source level debugger A simulator allows for early debugging and execution of algorithmic code It does not require any target hardware A source level debugger lets you step through your code stop it and then examine memory contents and program variables Explanation In circuit emulator ICE and JTAG debugger An Emulator emulates the behavior of the real chip ICEs allow you to replace the real chip that interacts with I
48. through events The coordinator records the score and outputs messages to the terminal After the game finishes the program ends but make sure the main method never returns otherwise the BTnode reboots and starts a new game HINT The ball will be responsible for deciding whether or not it hits the table i e whether the player hits the ball well or not In order to decide whether a ball hits the table we will use a random number generator At the beginning of the program you will need to include stdlib h and initialise the random number generator by calling srand u int seed From then on every call to rand will give a number between 0 and RAND MAX so in order to get a random number r number between and b a lt lt b use a rand A b a Experiment with different player qualities i e using a higher probability of playing a good ball and see how it influences the result Make ample use of NutSleep in order to make the game watchable on the terminal window 41 Chapter 6 Embedded Debugging 6 1 Introduction The goal of this tutorial is to get to know the different tools and techniques for embedded debugging considering the BTnode platform as example One of the most compelling problems for anyone programming an embedded system is to understand what your system is doing what resources it s using and how it interacts with the external world Bugs occur Fixing them is usually easier than finding
49. u long baud 57600 btn hardware init NutRegisterDevice amp APP_UART O 0 freopen APP_UART dev_name r stdout ioctl fileno stdout UART_SETSPEED amp baud To read data from the terminal you can use the function fscanf Optional Exercise 3 8 Write a program that samples the battery voltage once every two seconds using a timer ISR Instead of displaying the result on the LEDs print it to the terminal from within the ISR Measure the execution time of the ISR using the oscilloscope The measurement of the execution time of the ISR shows that printf takes a lot of time We have discussed before that ISRs should be as short as possible Therefore we want to do the printing of the sampled battery voltage from the main routine Of course we want to print every measurement result exactly once Exercise 3 9 Rewrite the program from Ex 3 8 such that the battery voltage is sampled in the ISR but that the printing of the result is done in the main routine To do this you have to think about some communication mechanism between the two flows of control Optional Exercise 3 10 Instead of printing the result from reading the ADCL and ADCH registers directly print it in millivolts HINT Remember that an unsigned short variable overflows at 65536 thus be careful about the data types you use The program you have written probably works just fine But if you would have a lot of time to observe its behavior or
50. with B Tnut A thread is simply a function or a small program that can run concurrently to another thread Using threads we can actually write B Tnode programs that listen to incoming commands over their radio periodically measure sensor values compute intermediate results and send data to other nodes All virtually at the same time This multithreading is handled by Nut OS as obviously our ATmegal28 microcontroller can only handle one instruction at a time In order to support multithreading or multitasking on a single core processors the operating system needs to repeatedly start and stop individual threads i e schedule in a completely transparent fashion Two general approaches to multithreading exist e Preemptive The OS has complete control over processes and can stop pause and restart them al most at will Most modern PC operating systems e g Linux Windows 2000 XP use preemptive multitasking This is because it allows for a more reliable distribution of resources e Cooperative Processes need to manually give up control of the CPU to a central scheduler which then evaluates which thread or task should come next based on process priorities and queues While cooperative multithreading simplifies resource sharing and usually results in faster and smaller code making it thus more suited to embedded systems programming it runs the risk that a poorly designed or hung process can bring the entire system to a halt
51. 0 the Mode changes to OFF again as it was before we typed trace oneshot but now contains O elements is replaced by is full es ex3 trace TRACE STATUS Mode is OFF Size is 500 is full SYNTAX trace print lt size gt oneshot circular size lt size gt stoplmask lt tag gt 3 In the previous step we have filled the trace buffer with events We now can have a look at them by typing trace print 10 which gives you an output like this es ex3 trace print 10 TRACE contains 500 items printing 10 items TAG PC Info Time s ms us 46 CHAPTER 6 EMBEDDED DEBUGGING Thread Yield idle 13 524 336 Thread Sleep LED 13 524 604 Thread Yield idle 13 581 857 Thread Sleep LED 13 582 125 Thread Yield idle 13 639 392 Thread Sleep LED 13 639 659 Thread Yield idle 13 696 909 Thread Sleep LED 13 697 205 Thread Yield idle 13 754 442 Thread Sleep LED 13 754 710 In the TAG column you see the type of the recorded events In the case shown above all events are of type Thread Yield or Thread Sleep the column Info shows you the name of the thread which has done a sleep or a yield and the Time column indicates at what time this was done The time is 0 when the BTnode is booted The list of events does not allow you to quickly understand what is really going on Therefore we now use the terminal program on the host computer to capture the terminal output in a file Then we postprocess the trace file we have created in the previous ste
52. 01 first byte of OpCode pkt payload 1 0x04 second byte of OpCode pkt payload 2 0x05 total length of parameters pkt payload 3 0x33 GIAC pkt payload 4 0x8b GIAC pkt payload 5 0x9e GIAC pkt payload 6 0x05 inquiry length 5 1 28s 6 4 seconds pkt payload 7 0x05 maximum number of devices Solution 7 3 send an inquiry command and use the Btstack thread to receice the answers include lt sys tracer h gt include lt hardware btn hardware h gt include lt terminal btn terminal h gt include lt stdio h gt freopen include lt dev usartavr h gt NutRegisterDevice APP_UART UART_SETSPEED include lt led btn led h gt needed together with btn_led_init 0 maybe a bug 7 include lt bt bt_hci_dispatch h gt for the setWaitQueue command include lt sys event h gt for NutEventWait and NUT WAIT INFINITE include lt bt bt_hci_cmds h gt for sending hci commands define HCI COMMAND DATA PACKET 0x01 define HCI_OGF_LINK_CONTROL 0x01 define HCI_OCF_LC_INQUIRY 0x01 define BT_HCI_HANDLE_INVALID OxFFFF struct btstack stack void init_stdout void u_long baud 57600 btn_hardware_init NutRegisterDevice amp APP_UART O 0 freopen APP UART dev name r stdout 113 _ioctl _fileno stdout UART SETSPEED amp baud print a single bluetooth device address to the terminal void print_bt_addr bt_addr_t addr printf 2x 2x 2x
53. 2 t cci000 tune manual uint32 t DesiredFreq interface TISM stands for Industrial Scientific Medial and denotes frequency spectrums that can be used without acquiring a license first 74 CHAPTER 9 THE CHIPCON RADIO static void init radio uint32_t desiredFrq uint32 t actualFrq bmac init NODE ADDRESS inits radio to 868 5 MHz actualFrq cc1000 tune manual desiredFrq reset radio frequency printf init radio set cc1000 to lu Hz n actualFrq ccc init amp bmac interface As this is still considered experimental no header file is yet available Simply include the interface as shown above Also the version contained in the 1 8 system release does not compile due to redefinitions be sure to use an updated version either from CVS or from the tutorial homepage Exercise 9 11 Manually set the frequency of one of your nodes to 868 5 Mhz the B MAC default frequency Observe the actual frequency that the CC1000 gets tuned to as returned by cc1000 tune manual and compare Can you still receive packets sent from this node on a node that is not manually tuned Explain why this works or does not work Optional Exercise 9 12 Extend your program from 9 6 so that each packet also contains the frequency on which the next packet should be sent use cc1000_set together with a number between 0 and 64 to choose from one of the 65 predefined frequencies Take packet loss into account i e
54. 2CAP_HCI_PACKET_TYPE 12cap_cmds_init l2cap_stack 1 BT L2CAP MIN MTU BT_L2CAP_MTU_DEFAULT rfcomm stack bt rfcomm init 12cap stack BT RFCOMM DEF MFS 4 5 rfcomm cmds init O bt cmds register cmds 122 APPENDIX B SOLUTIONS btn_cmds_register_cmds nut_cmds_register_cmds 12cap_cmds_register_cmds rfcomm cmds register cmds btn terminal register cmd sendsms send sms terminal mode btn terminal run BTN TERMINAL NOFORK 0 return 0 BIBLIOGRAPHY 123 Bibliography 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 Atmel Atmel ATmega128L 8 Bit AVR Microcontroller with 128k in System programmable Flash November 2004 J Beutel M Dyer M Hinz L Meier and M Ringwald Next generation prototyping of sensor networks In Proc 2nd ACM Conf Embedded Networked Sensor Systems SenSys 2004 pages 291 292 ACM Press New York November 2004 J Beutel O Kasten F Mattern K R mer F Siegemund and L Thiele Prototyping wireless sensor network applications with BTnodes In Proc 1st European Workshop on Sensor Networks EWSN 2004 volume 2920 of Lecture Notes in Computer Science pages 323 338 Springer Berlin January 2004 Chipcon CC1000 Single Chip Very Low Power RF Transceiver April 2002 ETSI Technical Specification 100 916 AT command set for GSM Mobile Equipment Version 7 7 0 1998 Bluetooth Special Interest Group
55. 3 hex avrdude load data flash data from input file bt cmd btnode3 hex avrdude input file bt cmd btnode3 hex contains 64478 bytes avrdude reading on chip flash data Reading iH HB HBEHHBEHBHHHBHHBEHHHHHBHHHHHHHHHHHHHHHHHE 100 4 17s avrdude verifying avrdude 64478 bytes of flash verified avrdude safemode Fuses OK 95 avrdude done Thank you make 1 Leaving directory home beutel eclipse btnut app bt cmd Solution 3 1 The blue LED is connected to pin 0 of port C Since port C is the upper byte of the address bus the value 0x0100 on the address bus switches on the blue LED Since the function write led shifts the argument value by 8 bits you have to use write led 0x01 to switch on the blue LED Solution 3 2 include lt hardware btn hardware h gt btn hardware init void shortpause u short duration 1 u short i for i 0 i lt duration i 1 ir void pause u_short duration u_short i for i 0 i lt duration i shortpause Oxffff void write_led u_char value volatile u_char pointer u_char dummy pointer u_char u_short value lt lt 8 dummy pointer sbi PORTB 5 asm volatile nop cbi PORTB 5 int main void 1 int toggle 0 Sbi DDRB 5 while 1 if toggle toggle 0 write led 0x01 else toggle 1 write_led 0x00 pause 12 return 0 d Solution 3 3 I have implemented the pause with the help of a s
56. 5 avr using BFD version 2 15 coff avr patch 20030831 C Documents and SettingsVes2005 avr gcc v Reading specs from C WinAVR bin lib gcc avr 3 4 3 specs Configured with gcc 3 4 3 configure prefix m WinAVR build mingw32 host mingw32 target avr enable langu Thread model single gcc version 3 4 3 C Documents and SettingsVes2005 avr ld v GNU ld version 2 15 coff avr patch 20030831 C Documents and Settings es2005 gt uisp version uisp version 20050207 C 1997 1999 Uros Platise 2000 2003 Marek Michalkiewicz uisp is free software covered by the GNU General Public License You are welcome to change it and or distribute copies of it under the conditions of the GNU General Public License C Documents and Settings es2005 gt avrdude v avrdude Version 4 4 0cvs Copyright c 2000 2004 Brian Dean http www bdmicro com System wide configuration file is C WinAVR bin avrdude conf avrdude no programmer has been specified on the command line or the config file Specify a programmer using the c option and try again Solution 2 11 avrdude help Usage avrdude options Options p lt partno gt Required Specify AVR device b lt baudrate gt Override RS 232 baud rate B lt bitclock gt Specify JTAG STK500v2 bit clock period us C lt config file gt Specify location of configuration file c lt programmer gt Specify programmer type D Disable auto erase for flash memory P lt port gt S
57. A has received event no 6 Thread A has received event no 7 main enters endless loop Thus we see that thread priorities DO play a role Note that the calls to the pause function are a quick hack that leads to a readable terminal output remember that printf implicitely does a NutThreadYield see exercise 5 1 Sample Code include lt stdio h gt include lt dev usartavr h gt include lt sys thread h gt include lt sys timer h gt 111 include lt sys tracer h gt include lt sys event h gt include lt hardware btn hardware h gt include lt led btn led h gt include lt string h gt HANDLE event void shortpause u_short duration X u short i for i 0 i lt duration i 1 y void pause u short duration 1 u short i for i 0 i lt duration i 1 shortpause Oxffff int init_stdout void u_long baud 57600 sbi PORTD 2 NutRegisterDevice amp APP_UART 0 0 freopen APP_UART dev_name r stdout _ioctl _fileno stdout UART SETSPEED amp baud return 1 I THREAD my thread arg 1 int count 0 if strncmp A runningThread td name 1 0 NutThreadSetPriority 10 for f NutEventWait amp event NUT WAIT INFINITE count pause 12 int main void int count 7 init_stdout NutThreadCreate A my thread 0 192 NutThreadCreate B my thread 0 192 while count gt 0 NutEventPost amp event printf main posts an event n
58. DE PROGRAMMING PFO PF7 PA7 PCO PC7 z z x x PORTF DRIVERS PORTA DRIVERS PORTC DRIVERS DATA REGISTER DATA DIR DATA REGISTER PORTF REG PORTF PORTA AVCC INTERNAL OSCILLATOR WATCHDOG TIMER OSCILLATOR MCU CONTROL gt TIMING AND REGISTER 1 0 CONTROL TIMER J COUNTERS 4 BH INTERRUPT 4 UNIT lt AGND AREF PROGRAM COUNTER E PROGRAM FLASH INSTRUCTION REGISTER INSTRUCTION DECODER CONTROL LINES BOUNDARY SCAN PROGRAMMING LOGIC GENERAL PURPOSE REGISTERS T m z e USARTO p ANALOG COMPARATOR PORTE DRIVERS PORTD DRIVERS PORTG DRIVERS PEO PE7 PBO PB7 PDO PD7 PGO PG4 Figure 2 2 Atmel ATmegal281 microcontroller core and peripheral block diagram Exercise 2 1 Find the BTnode rev3 20 Schematic and the ATmega128l Processor Manual pdf files T Browse the schematic and find the latch Texas Instruments SN74LVC573A used to multiplex the extended SRAMs AMIC LP62S2048 data and address bus Which ports of the processor are used to connect to the latch Which ports are used to connect to the memory Browse for the second latch used to multiplex the LEDs and switchable power supplies Which port pin on the 1281 maps to which function LED power switches here Which are the control lines used for the latch Draw a sample ou
59. DRB 1 lt lt DDB5 while 1 battery power get battery voltage if battery power below 1000mV switch on red LED if battery power between 1000mV and 2000mV switch on yellow LED if battery power above 2000mV switch on green LED wait a second switch on blue LED wait a second return 0 We now have a more detailed look at the function get_battery_voltage Its skeleton looks as follows int get_battery_voltage void configure ADMUX ADMUX 1 lt lt MUXO ADMUX 1 lt lt MUX1 configure ADCSRA register such that the conversion is as slow as possible and the ADC is enabled start conversion and wait for result read and convert result In a first step the ADMUX register is configured As you can see in the manual page 244 all bits are cleared at startup and we only have to write the bits which we want to be one Looking at BTnode schematics we 22 CHAPTER 3 DEVICE LEVEL PROGRAMMING see that the BAT SENSE signal is connected to pin of port From the manual page 239 we know that this pin is the third channel of the ADC and table 98 on page 244 tells us that we have to set the bits MUX1 and MUXO from the ADMUX register to sample the voltage from channel three We leave the ADLAR bit cleared The REFS1 and REFSO bits are left cleared because we use the external voltage reference connected to the AREF pin of the ATmegal28 WARNING DO NOT USE OTHER SETTINGS FOR THE REFSx B
60. Even though the execution coordination of these threads is done by the operating system we still need to properly code concurrent threads especially when it comes to two or more threads using a common resource e g the radio or the ter minal Threads will be described in the following chapter where we introduce the API of the B Tnut OS for creating executing and terminating threads as well as for the communication and coordination of such threads The following sections will explain the anatomy of a simple BTnut program using the example of LED control section 4 2 Section 4 3 will then explain how we can use BTnut to provide output over a terminal connection i e through the USB cable 4 2 Anatomy of a BTnut Program Recall from chapter 1 that BTnodes run an embedded systems OS from the open source domain called Nut OS Nut OS is designed among others for the Atmel ATmega128 microcontroller which is used on the BTnodes and is thus an excellent base on which the B Tnut extensions provide additional device drivers to access BTnode specific hardware The actual compilation of your programs i e the translation of C code into machine code is done using gcc avr part of WinAVR on Windows which is a freeware C compiler and assembler for the Atmel processor platform We thus have three parts to our B Tnode OS experience the rudimentary C libaries as implemented by gcc avr s avr libc the higher level OS routines built on top o
61. INITE 92 APPENDIX B SOLUTIONS prea Paces T is ions EET POJEM gt Hie Lat evige search Project Window Hep m ae Sg Sr e Or o v ore sam Sync Cvs Repost a cts 8 ela Binary Farser EE Pars FF Enable build output Load buld output from fie Figure B 1 Use the Eclipse menues to navigate the the new projects wizard Solution 2 6 The Atmel AVR is a family of simple yet very versatile microcontrollers based on an 8 bit RISC core running single cycle instructions AVR instructions are tuned to decrease the size of the program whether the code is written in C or Assembly The AVR Libc implements simple fixed point arithmetic functions using commands from the AVR instruction set such as 1ds xor or fmul Due to it s simple core architecture mathematical operations requiring complicated processor hardware such as multiply and divide are omitted However there are specialized libraries available that implement sets of mathematical functions fixed point anf floating point or even cryptography on the AVR architecture Some examples with online resources are e mikroPascal for AVR e mikroBasic for AVR e Procyon AVRlib Solution 2 10 93 C Documents and Settings es2005 gt avr as version GNU assembler version 2 1
62. ITS IT COULD DE STROY THE MICROCONTROLLER Exercise 3 4 Now its your turn to configure the ADCSRA register For maximal precision we want the slowest conversion speed We do not use interrupts and we want to do a single conversion After having configured the ADC the conversion can be started This is done setting the ADSC bit of the ADCSRA register This bit is automatically cleared when the conversion is completed Wait for this condition and then read the result from the ADCL and the ADCH register Determine the values you expect from the ADC for a battery voltage of 1 volt and 2 volts knowing that the reference voltage is 3300 millivolts the ADC delivers 10 bit values and the BAT SENSE signal is half the battery voltage see schematics HINT If your conversion result is always zero make sure that i you either have batteries in your BTnode or you have connected the battery contacts to an external power supply and that ii the power switch is on if connected to the USB cable the BTnode is also powered if this switch is off but then the BAT SENSE signal is 0 3 4 Writing interrupt routines Hardware Timers In this section the program from the previous section is modified such that it periodically samples the battery voltage in a timer interrupt routine The advantage is that now the microcontroller can do other work in parallel The processor load created by the timer interrupt is measured using an IO pin and the oscilloscop
63. It is nothing unusual HINT During the pairing process the BTnode sends the default hard coded PIN code 1234 Upon successfully creating the connection the following line is printed to the terminal RFCOMM Connect on dlci 2 At this point no more functionality is provided so just close the connection HINT The connection handle DLCI of a connection om channel 1 is always 2 If you have constant problems setting up the RFCOMM connection use a longer sleep period in the prepa ration step e g NutSleep 500 The following functions from the bt bt_rfcomm h library have been used in the previous exercise to open and close an RFCOMM connection They will be needed in exercise 8 3 60 CHAPTER 8 INTERFACING TO HANDHELD DEVICES Explanation bt start session u char bt rfcomm start session bt addr t bt addr u char page scan rep mode u_short clock offset This function opens an L2CAP channel to a remote device if it has not been opened yet The argument bt addr is the Bluetooth address of the remote device For the other two arguments a 0 can be passed on to the function if no other knowledge available The function returns 0x00 if channel set up was successful Explanation bt rfcomm connect u_char bt rfcomm connect u char channel nr BT RFCOMM CON CB BT RFCOMM RCV CB BT RFCOMM LINE CB BT RFCOMM CREDIT CB u char credit limit void cb arg This function establishes an RFCOMM connection on th
64. Mutezes in BTnut OS Shared resources can be used exclusively by a thread by signal ing current use over a mutex After defining a mutex using NutMutexInit amp myMutex threads can use NutMutexLock and NutMutexUnlock to reserve the resource managed by the mutex include lt hardware btn hardware h gt include lt dev usartavr h gt NutRegisterDevice APP_UART UART_SETSPEED include lt stdio h gt include lt io h gt include lt sys thread h gt include lt sys mutex h gt MUTEX myTerminal THREAD my thread arg for 55 f NutMutexLock amp myTerminal printf This is Thread One n NutMutexUnlock amp myTerminal NutThreadYield void init stdout void int main void btn hardware init NutMutexInit amp myTerminal init stdout as defined previously if 0 NutThreadCreate ThreadOne my thread 0 192 printf Sorry could not create ThreadOne Stopping Wn for 53 for 55 NutMutexLock amp myTerminal printf This is the Main Thread n NutMutexUnlock amp myTerminal NutThreadYield Exercise 5 10 Rewrite the program from Ex so that each thread first acquires a mutex lock before printing to the terminal Exercise 5 11 Write your own little thread safe printf function that uses mutexes in order to exclusively acquire use of the terminal HINT You can either use a separate function call e g my printf or a pre processor
65. T1 NO SW FLOWCONTROL I btnode include I nut include bt cmd c o bt cmd btnode3 o avr gcc bt cmd btnode3 o lib btnode3 nutinit o Wl start group L lib btnode3 mmcu atmegai28 Wl defsym main 0 Map bt cmd btnode3 map cref L lib btnode3 Inutos lnutdev lnutarch lnutcrt lbt lhardware lcm leepromdb lsuart lled lcc ldebug lmhop lsync lutils lterminal lsupport lcdist Wl end group o bt cmd btnode3 elf avr size bt cmd btnode3 elf text data bss dec hex filename 60416 4062 2814 67292 106dc bt cmd btnode3 elf avr objcopy 0 ihex bt cmd btnode3 elf bt cmd btnode3 hex rm bt cmd btnode3 elf make btnode3 upload make Nothing to be done for btnode3 make burn btnode3 make 1 Entering directory home beutel eclipse btnut app bt cmd avrdude pmi28 cavrispv2 Pusb s U flash w bt cmd btnode3 hex i avrdude AVR device initialized and ready to accept instructions Reading JHHHHHHEHBHHBHHHHHHHHHHBHHHHHHHHHHHHHHHHHHHHHHHHHHHRR 1004 0 01s avrdude Device signature 0x1e9702 avrdude NOTE FLASH memory has been specified an erase cycle will be performed To disable this feature specify the D option avrdude erasing chip avrdude reading input file bt cmd btnode3 hex avrdude writing flash 64478 bytes Writing fHHHHHHHHHHEHHHHHHHHHHHHHHHHHHHHHHHHHHHBHHHHHHHHNHE 100 5 19s avrdude 64478 bytes of flash written avrdude verifying flash memory against bt cmd btnode
66. TimerStart will automatically remove that timer after it has run once i e after one interval using 0 instead installs a periodic timer 32 CHAPTER 4 THE BTNUT OPERATING SYSTEM Exercise 4 7 Write a program with two timed callback functions one should repeatedly turn on the blue LED using btn Led set LEDO and switch off the red LED using btn_led_clear LED1 the other shall do the opposite i e turn on the red LED and switch off the blue LED Optional Exercise 4 8 Write a program that periodically calls a function to shift the current LED by one position after the last position it should begin again with the first Optional Exercise 4 9 Create a terminal application that allows to control the LED shifting functionality implemented in Ex i e use btn terminal register cmd to create a command toggle that turns the shifting on or off 4 5 Dynamic Memory Management Typically there is no need for dynamic memory management in your BTnode program Simply create global or local variables and the B Tnut OS together with gcc avr will take care for you to properly allocate the ATmegal28 SRAM of which we have 64kBytes for the stack and the global and or static variables However should the need arise e g you might want to limit the stack size of your current thread or you have temporary data that is very large B Tnut also supports dynamic memory allocation using malloc and free Expl
67. Timerl and Timer3 respectively These simply work as counters i e they continuously count from 0 to 255 or 65535 and begin again from 0 afterwards Whenever the counter overflows i e starts again at 0 an overflow interrupt can be triggered which allows a program to periodically execute a certain command While TimerO is already in use in BTnut to drive its timer functions e g NutTimerStart but also NutSleep 84 CHAPTER 10 BTNODES AND SENSORS the remaining timers are available for use in your BTnut program Using a number of processor registers one can customize the behavior of these counters For example by writing to the OCRx register x being 0 1 2 or 3 we can set the so called TOP value i e the value at which an interrupt should be triggered One can also switch a timer to the so called Clear Timer on Compare CTC mode where it restarts counting at zero whenever the counter reaches the TOP value otherwise it continues to the 8 bit or 16 bit maximum 6 Counters run at most with the speed of the main CPU which runs at about 7 37MHz in the case of the ATmegal28L on the BTnode Using a so called prescaler the counter can be slowed by factors of 8 64 256 or 1024 This can be set in the Timer Counter Control Register TCCRxn with x being 0 1 2 or 3 and n being A B or C for the two 16 bit counters only Explanation Using a hardware timer in BTnut The ATmegal28L hardware timer counter must be accesse
68. UPT6 NUT IRQMODE EDGE NutIrgEnable amp sig_INTERRUPT6 What happens if an interrupt occurs during such an ISR BTnut does not support stacked interrupts so the current ISR will first be finished When the system exists an ISR and finds another interrupt waiting i e its corresponding interrupt bit is set it will continue with executing the ISR of the next interrupt However while the current ISR was still running there might have actually been multiple identical interrupts e g a certain value crossed a threshold not only once and threw an interrupt but twice or more often As there is only one flag to indicate whether an interrupt has fired there is no way to know how many interrupts have been missed during the execution of the current ISR It is therefor important to keep the code inside an ISR as short as possible in order to minimize the chances of missing out on important other interrupts e g incoming packets on the Chipcon or Bluetooth radio Another factor that should not be underestimated is the time it takes the system to switch between the main program and an ISR typically tens or hundreds of CPU cycles in order to save the current system state and switch to an ISR and again back to the main program This uninterruptability of ISRs is sometimes also needed within the main program For example certain 16 bit registers of the AT mega128L need to be written to in an atomic fashion e g either both bytes ge
69. a thread implies a NutThreadYield i e setting its state to READY thus potentially yielding the CPU to another thread This is the case if the running thread reduces its priority and is thus no longer the thread with the highest priority that is ready to run Exercise 5 4 Take the program from Ex 5 1 and give the self created threat a higher priority Compare the output with the original program from Ex Repeat the experiment giving the self created thread a lower priority What do you observe Optional Exercise 5 5 Repeat Ex 5 5 but give the additional thread a higher priority Compare the output with what you received in Ex Repeat the experiment giving the additional thread a lower priority What do you observe 5 4 SHARING RESOURCES MUTUAL EXCLUSION MUTEX 37 Optional Exercise 5 6 Repeat Ex but use NutSleep instead of NutThreadYield Why is the output different from Ex 5 3 2 Explanation Terminating Threads A thread can terminate itself as shown below THREAD my_thread arg for f do something if some condition NutThreadExit There is no easy way for some thread A to kill another thread B Nevertheless you will implement this functionality in Ex 5 13 Combining thread creation with our means of writing command line applications for the terminal see section 4 3 we can experiment with thread creation and termination more conveniently Exercise 5 7 Write a program th
70. ader file Right click the function name again and search for All References in the Workspace Be sure to switch to the C C Perspective in Eclipse and open the C C Projects View see figure 2 4 C C bt cmd c Eclipse Platform _ File Edt Navigate Search Run Project Window ry IB G G O Q Svr Bil c c acvSReposto Resource C C Projects 3 Navigator SO 8 bt emd c 3 Emake Ta 23 0 67 T 5 ie s o E bat nsi EL btnut_snap GE snap a 28 05 app 71 Sa Ew M Es bootloader 8 05 73Yint main void al ni Gem 75 serial baud rate amp belego bootloader 76 w long baud 115200 E E btstreamer bt cmd bitest 9 18 bt cmd h 78 hardware init dean ER cmds h 79 btn hardware init 5 l2cap cmd bt emd c 80 btn led init 1 5 rfcomm cmd 8 18 cmds c 81 amp threads E E bt cmd btnode3 o 82 NES amp uart echo 8 Makefile 83 NutRegisterDevice amp APP UART 0 0 6 vartsuart bt and btnode3 hex 84 freopen APP UART dev name r stdout 8 05 doc Aube 85 ioctl fileno stdout UART SETSPEED sbaud idi d bt cmd btnode3 map a eb eas 87 hello world as printf P PSTR bt cmd app started booting bluetooth 1 89 30 bluetooth module on takes a while 8 09 ecapremd 91 btn hardware bt on 9 05 rfcomm cmd 92 Be 93
71. anation Dynamic Memory Allocation If you need to allocate memory directly you can use Nut OS s own malloc and free include lt hardware btn hardware h gt include lt stdlib h gt malloc free include lt string h gt memset u_int BUF_SIZE 4096 int main void char buffer btn_hardware_init buffer malloc BUF SIZE if buffer fill buffer with data memset buffer OxFF BUF SIZE and free it again really useful free buffer else out of memory for endless loop In addition to the 64kBytes of directly accessible SRAM the BTnode also features three banks of external data cache each having 60 kBytes for a total of 180 kBytes of external storage This memory cannot be allocated directly from within our BTnut program as our ATmega128 processor can only address 64 kBytes of RAM Instead one has to briefly switch the upper 60 kBytes of our regular SRAM with one of the three available banks in order to access data in there This functionality is implemented in the cdist xbankdata h and can be tested by including the terminal xbank cmds h commands See the sources of terminal xbank cmds c in the btnut sourcetree if you want to learn more about banked memory In this tutorial we will not further elaborate on this feature of the BTnut OS 33 Chapter 5 Programming with Threads 5 1 Introduction In this chapter we introduce thread programming
72. and say which simply sends off its arguments via broadcast and a corresponding packet handler that listens for such packets and writes their source and contents to stdout in a chat program fashion e g 45 says Hello world Optional Exercise 9 4 Extend the program from ez to take an address for the say command e g say 345 hello world Use say all or an additional shout command to initiate broadcasts Exercise 9 5 Write a program that periodically e g every 2 4 seconds sends out PING TYPE packets to the broadcast address A specific packet handler for these packets should print out a brief message everytime it receives such a packet Install your program on two BTnodes and observe them on two separate terminals 72 CHAPTER 9 THE CHIPCON RADIO Explanation The B MAC Packet struct A Chipcon packet is defined as shown below It not only contains the actual packet payload but also information about the packet s sender pkt gt src struct ccc packet t source of the packet u short src destination of the packet u short dst payload length u short length packet type u char type payload data u char data 0 Exercise 9 6 Change your program from ex so that PING_TYPE packets are only sent out after no packet has been received for some time use a timer Upon reception of a PING_TYPE package a PONG_TYPE package should be sent out and vice versa make sure that the t
73. ar function call does Therefore you would like to start tracing immediately before this function is executed You can do this as shown here include lt sys tracer h gt int main void initializations NutTraceMaskSet TRACE_TAG_INTERRUPT_ENTER NutTraceMaskSet TRACE_TAG_INTERRUPT_EXIT some code NutTraceInit 1000 TRACE_MODE_ONESHOT code you want to trace some code At the begin of the main routine you set the trace mask using the functions NutTraceMaskSet and NutTraceMaskClear You find the macros that describe the types of events you want to trace in the sys tracer h header file Then you start the trace using NutTraceInit immediately before the code you are interested in The first parameter of this function determines the amount of items that are traced the second parameter specifies whether tracing should be stopped when the trace buffer is full TRACE_MODE_ONESHOT or whether it should continuously overwrite the entries TRACE_MODE_CIRCULAR until tracing is stopped explicitly The program shown above now automatically fills the trace buffer You can either print it using the trace terminal command or using the function NutTracePrint which takes a single argument that determines how many trace entries shall be printed If this argument is 0 the whole buffer is printed Exercise 6 9 Trace the printf function First use a string that is shorter than the length of the buffer default is 64 ma
74. at registers the command create as a terminal command This com mand takes a string argument and creates a thread with this name This thread periodically prints its name on the terminal and then sleeps for a second HINT A thread can access its own name using runningThread td name e g using printf s ready n runningThread gt td_name Optional Exercise 5 8 Rewrite the program from Ex such that the first thread you start sleeps for one second the second thread sleeps for two seconds etc HINT For this purpose you may use the third argument of the NutThreadCreate to pass the sleep time to the thread Another alternative would be to use a global data structure Optional Exercise 5 9 Rewrite the program from Ex so that the create command takes a second parameter specifying the stack size of the thread that is created Use this command and nut threads to figure out how much stack is actually used by the threads you create Add some local variables to these threads and or call some dummy functions from these threads to see how this increases the amount of used stack 5 4 Sharing Resources Mutual Exclusion Mutex Ex showed the problem of two or more threads trying to access the same resource the terminal concurrently As a result their output was garbled One way to coordinate shared resources is the use of a mutex a lock mechanism for mutual exclusive resource usage 38 CHAPTER 5 PROGRAMMING WITH THREADS Explanation
75. ate a new folder in the app directory and copy the bt cmd Makefile to this folder Create or alternatively copy and rename a new application c file in this folder Be sure to edit the project name in the Makefile Now you are ready to program your first own project using BTnut Explanation Resetting the work environment to initial conditions The pre compiled BT nut snapshot used in this tutorial can be obtained from http sourceforge net projects btnode sec tion Files Download the btnut_snap_btnode3_binary_x x tar gz file and unpack it to a location of your choice Now create a new Standard C C Project in Eclipse and import the files from the btnut_snap_avrbinary archive Optional Exercise 2 20 In order to stay up to date on the bleeding edge development codebase of BT nut you will need to check out the most current version from the CVS repository on sourceforge net Open the CVS Repository Exploring perspective in Eclipse and create a new CVS repository Host btnode cvs sourceforge net Repository path cvsroot btnode 2 5 FIRST STEPS IN BTNODE PROGRAMMING USING THE AVR GCC TOOLCHAIN 17 User anonymous Connection type pserver The check out the CVS HEAD of the module btnut as a Standard Make C Project You can check for changes to the most current CVS tag HEAD or to other dates and tags by selecting Compare With or Replace With Before building the demo applications in the app directory you will need to c
76. buffer for i 0 i lt length i if i length if base 0 0 character bin2int base itoa character base 16 if strlen base 1 base 1 base 0 base 0 0 base 2 0 strcat message str base break character character value message i if character 1 strcpy buffer 0000000 itoa character rdbuffer 2 strcpy buffer 7 strlen rdbuffer rdbuffer if i 0 amp amp i48 0 strncpy carry buffer 7 i 8 i48 carry i48 0 strcat carry base character bin2int carry itoa character carry 16 if strlen carry 1 carry 1 carry 0 carry 0 0 carry 2 0 strcat message str carry strncpy base buffer 7 1 8 base 7 i 8 N0 elsei strcpy base buffer elsei ERROR Not a valid character 66 CHAPTER 8 INTERFACING TO HANDHELD DEVICES Exercise 8 5 In this exercise you are asked to implement functionality to completely assemble a PDU of an SMS message and to send this PDU over RFCOMM to your cell phone 1 Add another function to your source file This function should take the recipient s phone number and the message string as input parameters 2 In this function assemble the PDU Use the function implemented in the previous optional exercise or the sample solution for message encoding 3 Also insert the code for the necessary AT Commands to make the cell phone dispatch the SMS message
77. cation to your BTnode Download the newest example application file bt cmd btnode3 hex from the BTnode project sourceforge net file release page Open a com mand line shell In this step you will two use avrdude commands that are executed by the ISP programmer erase and upload First erase any programs present in the flash memory of the ATmega128l using erase 14 CHAPTER 2 FIRST STEPS IN BTNODE PROGRAMMING Figure 2 6 Debugging a BTnode using a USB connection to a serial port and ISP programming with the Atmel ATAVRISP avrdude pm128 cavrispv2 P dev ttySO e Then program the new application code from an Intel Hex file format to the BTnode using upload avrdude pm128 cavrispv2 P dev ttySO D V s U flash w bt cmd btnode3 hex i The D flag disables the auto erase function the V flag disables auto verify and the s flag requires safemode You can add the v flag to receive more verbose output Observe the LEDs on the BTnode for output from your first uploaded program Explanation Installing the bootloader Download the newest bootloader file bootloader btnode3 hex from the BTnode project sourceforge net file release page To install the bootloader proceed to upload this program code to the BTnode using the ISP programmer as described analogously for bt cmd btnode3 hex in exercise Now your BTnode is ready to receive software flash reprogramming instructions To compile your own bootloader navigate to the btnut_system bt
78. cially suited for sensor networks called clear channel assignment CCA It also offers an equally low power oriented approach to listening for incoming data called low power listening LPL Just as any other MAC protocol B MAC detects transmission errors for us handles acknowledgements and provides an addressing scheme Overall however B MAC is a rather simple protocol that minimizes protocol overhead while providing essential support for low power communication 9 2 Accessing the CC1000 Three main modules and a number of helper modules implement control of the CC1000 radio on our BTnode The low level access to the radio i e the physical layer resides in cc1000 c the B MAC protocol the data link layer is implemented in bmac c and the high level routines for sending and receiving data are in ccc c This modular setup allows the use of multiple MAC protocols though so far only a single one is available Figure 9 1 gives an overview of the dependencies Unless you want to program your own 1Note that they don t even have to be in range of each other if a third receiving node sees both of them This is known as the hidden terminal problem In the ISO OSI network reference model the physical layer layer one would be our Chipcon radio while the MAC would be situated in layer two the data link layer 3Its authors explicitly encourage the implementation of more sophisticated MAC protocols on top of B MAC 12 Speci
79. d again from exercises and 1 4 We can visualize the currently active threads using the nut threads command see Predefined Terminal Commands on page 30 bt cmd 00 d2 nut threads Hndl Name Prio Sta QUE Timr StkP FreeMem 2057 T TERMIN 150 RUN 0385 0000 200D 950 OK 2057 OD6A 14A4 LED 150 SLP 0000 2088 1481 989 OK 1087 main 64 SLP 0000 2074 1064 733 OK OD6A idle 254 RDY 0385 0000 OD4E 356 OK 2057 OD6A In order to have all of these standard threats running at the same time we also need to make sure that all of them repeatedly yield the CPU to other threats As the idle LED and terminal threat are all coded for us by the OS programmers who thoughtfully made all of these threats yield every so often we only need to make sure that the main threat which is under our control does so as well Exercise 5 2 Use the minimal BTnut program as described on page 28 and add a LED heartbeat see page 128 and the predefined Nut OS terminal commands see page 39 Start the terminal in a new thread using btn_terminal_run BTN_TERMINAL_FORK 0 but leave the main routine empty i e use only for Do you see the LED heartbeat Can you interact with the terminal Fix your program so that both heartbeat and terminal thread can be executed concurrently to your empty main program HINT See and zz 36 CHAPTER 5 PROGRAMMING WITH THREADS Explanation Controlling the LED Thread Initializing our LEDs with btn_led_init
80. d arg printf rfcomm Line status has changed dlci d flags 02x n dlci flags void credit_cb u_char dlci u_char credits void arg printf rfcomm Credits running low for dlci d Credits remaining d n dlci credits printf rfcomm Send new credits d n MAX CREDITS credits bt rfcomm send credits dlci MAX CREDITS credits returns the 7bit ASCII value of a character int character_value char character Lookup table for 7bit ASCII code const char alphabet 128 70 09 09 070 00 09 009 v 0 oo r 202 202 0 0 009 009 009 0 009 0 202 7 3 p mmay up v 52 NY Xu 3j 2582 2 M 23 VP 20 21 222 32 6 N89 297 Ag te Br GP 32 222 2 7Q 2A 20 202 gt E C H 22 j 2127 2M o Pas 2 Ry 28 T U2 uw fX AY 327 0 Q o a p PCPs 677 fj ul Th 2125 A gt SIS S P o0 p ug Hp g u uw ow xt p 1235 20 o 2 Q int i 1 0 1 lt 128 if character alphabet 1 return i return 1 no valid character convert binary to integer int bin2int char binary int i int sum 0 int length length strlen binary for i 0 i lt length i if binary i 1 sum int pow double 2 d
81. d btn led h gt 110 APPENDIX B SOLUTIONS HANDLE event int init stdout void u_long baud 57600 sbi PORTD 2 NutRegisterDevice amp APP_UART 0 0 freopen APP_UART dev_name r stdout _ioctl _fileno stdout UART SETSPEED amp baud return 1 THREAD my thread arg 1 int count 0 for NutEventWait amp event NUT WAIT INFINITE count printf myThread has received event no d n count int main void 1 init stdout NutEventPost amp event printf main posts an event n NutEventPost amp event printf main posts an event n NutThreadCreate myThread my_thread 0 192 printf main enters endless loop n for NutThreadYield return 0 Solution 5 16 The output received is Thread A has received event no 1 Thread B has received event no 1 Thread A has received event no 2 Thread B has received event no 2 Thread A has received event no 3 Thread B has received event no 3 main enters endless loop Thread A has received event no 4 Thus we see that every event is received ONLY by one thread even though two threads are waiting Since both threads have the same priority they are served in turns When line 80 NutThreadSetPriority is included then the output is Thread A has received event no 1 Thread A has received event no 2 Thread A has received event no 3 Thread A has received event no 4 Thread A has received event no 5 Thread
82. d directly through the corresponding hardware registers The four timer are started by setting their corresponding prescaler value to non zero value see above Also one needs to set the count at which an interrupt and or a reset to 0 should be triggered as well as indicate what counter mode should be used normal CTC etc include lt sys atom h gt u_char max 128 set counter mode to CTC see ATmegai28L manual p 156 in Timer Counter2 Control Register TCCR2 sbi TCCR2 WGM21 cbi TCCR2 WGM20 set prescaler to 1024 slowest timer possible see p 157 sbi TCCR2 CS22 cbi TCCR2 CS21 sbi TCCR2 CS20 make sure interrupts are turned off NutEnterCritical 0 register interrupt handler to be called for 8 bit counterO NutRegisterIrqHandler amp sig_OUTPUT_COMPARE2 my_timer2_handler NULL set TOP value i e when interrupt should be triggered OCR2 max reset current counter value to zero TCNT2 0x00 no need to start anything counter runs continuosly enable interrupts again NutExitCritical Exercise 10 7 What type of counter do you need to generate waveforms for the 7BB 12 9 buzzer of the BTsense sensor board You will have to take into account not only the desired signal frequency but also the speed of the processor and the possible values of the prescaler Hint The corresponding chapters in the ATmega128L manual contain a formula for computing a timer counter s freque
83. ddressed either directly to this node or those sent to a broadcast address More details about addresses can be found below The bmac enable led command activates LED feedback for sending and receiving i e the B MAC layer will light the green outermost LED when listening the blue innermost LED when sending or receiving and the red LED in case of CRC errors Exercise 9 1 Write a program that activates the CC1000 as described above including the B MAC LED activation before going in an endless NutSleep What do you observe Add terminal access to your appli cation and integrate the Nut OS command set using nut cmds register cmds Check the output of the nut threads command 9 2 ACCESSING THE CC1000 69 9 2 2 Sending Data Once we have initialized the radio we can use the ccc send command part of ccc h to send out data define MAX PACKET SIZE 8 define PACKET TYPE 0x01 application specific 0 255 pkt new ccc packet MAX PACKET SIZE void cmd send ushort char arg int val pkt gt length 4 if sscanf arg Zu amp val 1 sprintf pkt gt data u val if ccc_send BROADCAST_ADDR PACKET_TYPE pkt send failed lt gt O indicates error ccc_send takes as input the intended receiver s address the type of packet that should be sent and the packet itself Packets not only contain payload but also source and destination information an explicit size length as well as
84. de and libraries as well as transformation into a machine uploadable format of a sample application called test c avr gcc c mmcu atmegai28 D__BTNODE3__ I include test c o test btnode3 o avr gcc test btnode3 o lib btnode3 nutinit o L lib btnode3 mmcu atmegal28 o test btnode3 elf avr size test btnode3 elf text data bss dec hex filename 36920 1708 314 38942 981e test btnode3 elf avr objcopy 0 ihex test btnode3 elf test btnode3 hex 6 CHAPTER 2 FIRST STEPS IN BTNODE PROGRAMMING 2 2 2 Simulation and Debugging When project size increases and especially in critical situations specialized simulation and debugging tools can be of great benefit There are numerous tools available avr gdb JTAG tools Atmel AVR Studio GNU dwarf parser avr insight Avrora simulavr serving different purposes of which a selection will be introduced in chapter 6 2 2 3 Project Management The basic utility used in most build environments is GNU make The make utility automatically determines which pieces of a large program need to be recompiled and issues commands to recompile them This is a very convenient way to avoid retyping long lines of parameters on the command line Different editors with syntax higlighting and project management features can be used for C based AVR development The most common are Eclipse Emacs Programmers Notepad and AVR Studio Especially Eclipse in conjunction with CDT C C Development Tools is a very p
85. e Explanation Hardware Timers Another type of on chip resources are timers In principle timers are counters that are incremented automatically By the use of configuration registers the speed of incrementing the timers can be adjusted and whenever the timers overflow or reach a specified value they trigger an interrupt Explanation Interrupt Service Routines ISR Interrupts are used to execute a function the so called interrupt service routine The normal program flow the main function in our case is interrupted and the interrupt service routine is executed As soon as it terminates the normal program flow is resumed exactly at the position where it was interrupted Timer interrupts can thus be used to execute some periodic functionality without having to spend the whole processing time on waiting An example is shown here include lt hardware btn hardware h gt include lt dev irqreg h gt static void timer3IRQ void arg switch on green led int main void register interrupt service routine NutRegisterIrqHandler amp sig_OVERFLOW3 timer3IRQ 0 3 5 PROTECTING SHARED DATA AND RESOURCES 23 configure the speed of the timer TCCR3B 1 lt lt CS30 TCCR3B 1 lt lt CS32 enable the interrupt at overflows of the timer ETIMSK 1 lt lt TOIE3 while 1 toggle the blue led wait a second return 0 In addition to the main routine the interrupt service
86. e Optional Exercise 3 3 Once your program is running try to estimate the clock frequency of the AT 128 Do this by counting the operations in the loop of your pause function HINT Look at the list file program name gt Lst which has been created by the compiler Even without understanding any assembler at all you can find your function by searching for its name You can identify the loop by looking at the labels L6 for example and the branch instructions brio L6 for example Assume that all assembler instructions take one cycle to execute 3 3 On chip resource The Analog to Digital Converter The ATmegal28 microcontroller contains an on chip analog to digital converter ADC whose detailed description can be found on pages 231 to 247 of the AT megal28 manual As for all on chip resources the ADC can be configured by writing to special purpose registers its status and the conversion result can be accessed by reading from special purpose registers In the case of the ADC the two 8 bit registers called ADMUX and ADCSRA are used for configuration and status The two 8 bit registers called ADCH and ADCL are used to deliver the conversion result As we now know how to use the LEDs we can start writing more complex programs We now want to sample the battery power and show the result using the LEDs The solution should look as follows include lt hardware btn hardware h gt int main void int battery power D
87. e relatively high priority of 16 in order to prevent delaying packet reception This thread listens on a specific event handler for incoming data packets as signaled by the B MAC low power listening implementation and in turn calls type specific packet handlers for each received packet Packet handlers are registered using the ccc register packet handler function and must implement the void pkt handler ccc packet t pkt interface An example is shown below void pkt handler ccc packet t pkt 1 u short i if sscanf pkt gt data u amp i 1 printf Received Value u n i else error parsing stringified data packet define PACKET TYPE 0x01 int main void ccc_register_packet_handler PACKET_TYPE pkt handler Explanation B MAC Packet Handlers A packet handler is always assigned to a single packet type and will thus only be called when the ccc rec thread not only received a properly addressed packet but also one with a matching type These types are currently application specificy i e you need to define the necessary type IDs from 0 255 yourself For example an application might decide to define several such types in order to differentiate between status messages sensory data and routing information define SENSOR DATA 0x01 define ECHO REQUEST 0x04 define ECHO REPLY 0x05 define ROUTING TBL 0x09 Exercise 9 3 Write a small chat program consisting of a terminal comm
88. e 2 The three threads shall execute in turns which you implement with events One thread computes the square of the global variable the second decrements it by one and the third multiplies it by two All threads print the result on the terminal When the global value has reached a value greater than 10000 all threads except the main routine terminate themselves The main routine enters an endless loop Exercise 5 13 Extend the program from Ex with the terminal command kill that takes the name of a previously created thread as an argument The terminal thread shall use an event to inform the selected thread that it is supposed to kill itself Optional Exercise 5 14 What happens if first an event is posted by some thread A and only afterwards some thread B does a NutEventWait What happens if multiple events are posted before another thread is ready to receive them Are the events stored or lost Write a program to find out Optional Exercise 5 15 What happens if two threads are waiting for the same event Are both threads woken up Do thread priorities play a role Write a program to find out Exercise 5 16 Modify the program from Ex so that each created thread mostly sleeps e g using NutSleep 15000 and only briefly listens for a kill signal e g using NutEventWait amp killqueue 125 Observe what happens if you send a process a kill signal Does it eventually terminate Try changing the signal wait command to NutEventWaitNext a
89. e channel specified by channel nr BT RFCOMM CON CB BT RFCOMM RCV CB BT RFCOMM LINE CB and BT RFCOMM CREDIT CB are callback functions Use the value 10 for credit limit and the NULL pointer for the callback argument cb arg The function returns 0x00 if connection set up was successful Explanation bt disconnect u char bt rfcomm disconnect u char dlci This function closes an RFCOMM connection It expects the connection handle dlci as argument and returns 0x00 if the connection was successfully closed Explanation Callback Function Callback functions are often used in protocol programming The higher layer calls a lower layer function passing a function pointer as argument to it This allows the lower layer to execute a function that is defined on a higher layer Higher Layer Higher Layer Main Program Callback Function Main Program Callback Function calls Lower Layer Lower Layer calls Main Loop C Registration Function Main Loop Registration Function 7 8 3 AT Commands At the end of this section you will be able to send SMS messages from the BTnode As shown in section 8 2 an RFCOMM connection can be established between a BTnode and a cell phone Over this link Attention Commands AT Commands can be sent see the Bluetooth stack figure B 1 8 3 AT COMMANDS 61 Explanation AT Commands Originally the AT Commands were developed as a speci
90. e for the LEDs is put on the address bus It is assumed that it remains there until the latch is disabled in line 11 This is not the case if between lines 7 and 11 an interrupt occurs Thus an EnterCriticalO should be inserted before line 7 and an ExitCritical after line 11 O1 void write led u char value 02 03 volatile u_char pointer 04 u char dummy 05 06 pointer u char u short value 8 07 dummy pointer 08 09 Sbi PORTB 5 10 asm volatile nop 11 cbi PORTB 5 12 Solution 5 1 include lt sys thread h gt include lt hardware btn hardware h gt include lt led btn led h gt THREAD my_thread arg for 53 btn_led_clear LEDO btn led set LED1 NutThreadYield second yield to add then both LEDs are on int main void hardware init btn_hardware_init btn led init 0 NutThreadCreate my thread my thread 0 192 for 33 btn led clear LED1 btn led set LEDO NutThreadYield first yield to add then only red LED is on return 0 Solution 5 5 The terminal output should look like this my_thread is alive main is alive my_thread is alive main is alive my_thread is alive main is alive my_thread is alive main is alive my_thread is alive main is alive You would expect for both exercises the same output that of exercise The reason for the deviating behavior is that the mechanism that wakes up threads after a sleep
91. e random number These keys are then stored for further interaction To safely transmit the connection keys at this very first connection set up an initializing key has to be generated which in turn is calculated out of some random number one of the Bluetooth addresses and the Bluetooth PIN code If for example a connection between two cell phones is being established then first user A is asked to enter a PIN code can be arbitrary to its phone This code is then sent to B s phone B is asked to enter a PIN code as well which is sent back to A s phone If the two PIN codes match then a trusted pair is formed Preparation The current version of the btnut binaries is not compatible with connections to cell phones Therefore a patch has to be applied to the sources 1 Open the file bt_rfcomm c located in the folder btnut btnode bt 2 Search for case BT RFCOMM MSC CMD and insert the instruction NutSleep 1 on the following line 3 Compile the sources make install Exercise 8 2 Establish an RFCOMM connection to your cell phone on channel 1 For this purpose upload the demo application rfcomm cmd to the BTnode It is located in the folder app rfcomm cmd The following terminal commands will be needed e rfsession opens a connection e rfdiscon closes a connection To find out how to use the commands simply type the command and hit Enter This should show you the usage Don t panic if an error occurs during connection setup
92. e the latch 20 CHAPTER 3 DEVICE LEVEL PROGRAMMING PORTB 1 PB5 wait a moment asm volatile nop disable the latch i e hold the value PORTB amp 1 PB5 Explanation volatile Note the keyword volatile before the declaration of pointer It tells the compiler that code lines containing pointer should not be optimized at all This is necessary because the compiler does not know anything about external off chip resources like the LEDs Thus it cannot understand why we compute the variable dummy which is never used afterwards If volatile were omitted the compiler would simply ignore such nonsense statements Explanation Accessing special purpose registers The names of special purpose registers are defined in the hardware btn hardware h header file and in header files included therein These names can be used like variables For example you may read the content of the PORTB register using u char current portb PORTB Similarly you can write to such a register in the same way as you write to a variable e g PORTB Oxff sets all bits of the PORTB register to one Most often however you only want to read or write a single bit of a special purpose register This can be done by using the bitwise and or operators The names of individual bits are also defined in the header files But these names cannot be used like variables they are simple aliases for the position of the corresponding bit
93. eal time clocks In order to poll an I C sensor in BTnut we need to know its address on the I C bus Addresses are defined in the corresponding header file hopefully conflict free in btsense btsense h for the B Tsense board and under extras teco_ssmall for the ssmall board both of which use the I C compatible TC74 temperature sensor 9 Also we need to know the corresponding I C command that needs to be issued through the TwMasterTransact function This information can be found in the sensor s datasheet for the TC74 the datasheet lists 0x00 as the command code for reading a temperature value Explanation TWI Communication in Tnut NutOS comes with a simple two wire interface TWI library that works also on our ATmegal28L The most important commands are TwInit to initialize the interface and TwMasterTransact to send commands to and receive data from the individual sensors TwInit takes a sole argument a 7 bit slave address in order to allow in theory our master to also act as a slave to other masters on the bus However as the current implementation does not support slave mode for the ATmegal28L the parameter can safely be ignored set it to 0 for example TwMasterTransact takes as a first argument the slave device address followed by two variables each for sending and receiving data the address of the variable where the command can be found followed by its length and the address of the variable where the
94. eb browser and open the file btnode include led btn led h from the File List Read the documentation provided for the btn_led_init and btn_led_add_pattern functions Exercise 2 5 Go back to the bt cmd c file and add a new led pattern for the LED heartbeat using btn_led_add_pattern in line 108 While typing the function name btn_led_add_pattern press CTRL SPACE 2 4 BTNUT SYSTEM SOFTWARE RESOURCES 11 to invoke Eclipse s Content Assist function and complete the line with the correct arguments to create a dual blinking LED pattern using these parameters pattern BTN LED PATTERN HALF arg 0 Speed 10 nr BTN LED INFINITE Exercise 2 6 Check the documentation available in the datasheets application notes mailing list archives Nut OS webpage Avrfreaks forum tool resources etc to get an overview on the different compilers libraries programming variants and hardware programmers available for the Atmel AVR family Exercise 2 7 Open the avr libc Manual online version available on the avr libc webpage Find the math ematics functions in the avr libc and check what functions are supported Compare this selection to the CPU description found in the 1281 Manual and the instruction set of the 1281 found in the AVR Instruction Set Manual Don t forget to read the available footnotes to learn about device specific options Think about what functions you would like to use to implement certain algorith
95. ed snapshot contains 5 directories app for the applications doc for documentation extras for hardware specific drivers other than the BTnode include for all headerfiles and lib for the pre compiled libraries 10 CHAPTER 2 FIRST STEPS IN BTNODE PROGRAMMING The first task to be performed on the BTnut system software will be to set up a working environment within Eclipse Exercise 2 2 Open the C C perspective in Eclipse Create a new project called btnut snap X X by selecting Standard Make C Project from the pull down menu Be sure to set the correct binary parser on the second screen of the new project wizard select ELF parser and GNU ELF parser and enter avr addr2line and avr c filt and set the correct compiler avr gcc in the discovery options tab to select the correct cross development tools for the AVR platform Now import the btnode_snap_btnode3_binary package by selecting Import Archive File into this project As a final task you will need to configure the project with the correct include paths for the C C parser Open the project properties and insert the btnut_snap include PATH_TO_AVR_GCC_TOOLS avr include and PATH_TO_AVR_GCC_TOOLS lib gcc avr 3 4 5 include to the projects include paths Exercise 2 3 Open the bt cmd c file in the app bt cmd folder and go to the line where btn_led_init 1 is called Highlight the function name then press F3 to open the functions Declaration from the appropriate he
96. en using a timer to drive an actuator connected to one of these pins this has the advantage of not needing a separate interrupt service routine to explicitly set pin output to 1 or 0 the timer counter s corresponding will automatically alternate between 0 and 1 whenever the counter reaches its TOP and or BOTTOM value Explanation Putting a Waveform onto an I O pin in BTnut By connecting a device to the output pin of a 8 bit or 16 bit counter we can directly modulate a corre sponding signal onto the pin This only requires that we set the data direction register of this pin i e to define it as an output pin u short max 57535 example set counter mode to CTC see ATmegai28L manual p 131 in Timer Counteri Control Register TCCR1A cbi TCCR1A WGMO3 sbi TCCR1A WGMO2 cbi TCCR1A WGMO1 cbi TCCR1A WGMOO set up output pin OCR1A to be toggled by counter cbi TCCR1A COM1A1 sbi TCCR1A COM1A0 start counter with prescaler to 8 example see manual p 135 cbi TCCR1A CS12 sbi TCCR1A CS11 cbi TCCR1A CS10 make sure interrupts are turned off NutEnterCritical 0 no need for interrupt handler simply set TOP value OCR1 max reset current counter value to zero TCNT1 0x0000 enable interrupts again NutExitCritical enable pin output for 0 1 PB5 sbi DDRB PB5 Exercise 10 8 Describe the steps necessary to put a 440Hz signal on
97. en your elf file from the File gt Open File menu A project wizard appears Select AVR Simulator as debug platform and ATmegal28 as device The simulator initializes and stops at the first instruction Go to the AVR Simulator Options from the Debug menu and set the frequency to 8 00 MHz 44 CHAPTER 6 EMBEDDED DEBUGGING 4 In the I O workspace window on the left side you find all the simulated resources of the AVR Take some time to browse through the individual items Expand the PORTF item 5 Congratulations now you can step through your code F10 set breakpoints and watch how the ports and registers change in the workspace Optional Exercise 6 5 Profiling printf with AVR Studio Printf statements are often used for debugging Printing out variable values and function entry exit points allows you to discover how your program is operating In this exercise we measure the cycle count of an example printf statement in order to get the feeling of the overhead 1 Edit your nutsim c file include lt io h gt include lt stdio h gt include lt dev usartavr h gt include lt hardware btn hardware h gt int main void u long baud 57600 btn hardware init NutRegisterDevice amp APP_UART 0 0 freopen APP UART dev name w stdout _ioctl _fileno stdout UART SETSPEED amp baud printf UART baudrate 57600 5n for 2 Recompile the e1f file The simulator should automatically restart and load
98. ent See the corresponding BTnut source code in btnut cc cca c 75 Chapter 10 BTnodes and Sensors While the BTnode has been designed for conducting research in Wireless Sensor Networks WSNs it does not carry any onboard sensors This is in contrast to other WSN platforms such as the Tmote Sky which optionally comes with three onboard sensors temperature light and humidity The reason for not including a fixed set of sensors lies in its added flexibility depending on the particular application BTnodes can be equipped with seperate sensor boards that contain only the required set of sensors and which can be directly connected to one of the external connector sockets on the BTnode Working with sensors on the BTnode thus requires us to choose either a pre made sensor board or to connect our own set of sensors directly to one of the BTnode s connectors In this tutorial we will use the BTsense sensor board developed as part of the 2006 Wireless Sensor Network lecture at the ETH Zurich s Inst of Pervasive Computing It has been specifically designed to contain both analog light and digital temperature and motion sensors as well as an actuator buzzer It is connected through the BTnode s Debug Connector called J2 on the side and is designed to be attached e g with some plaster material to the side of the BTnode Figure 10 1 shows the top of the board In particular the BTsense board features the followin
99. ent over the UART Exercise 7 2 Open the Bluetooth specification om page 510 to figure out how HCI Command Packets are constructed in general You will find a detailed description of the Inquiry Command on pages 531 and 532 Figure out what the single entries of the following bt hci pkt cmd mean 7 2 DISCOVERY OF BLUETOOTH DEVICES 51 struct bt_hci_pkt_cmd pkt pkt pkt pkt pkt pkt pkt pkt pkt pkt type 0x01 payload 0 0x01 payload 1 0x04 payload 2 0x05 payload 3 0x33 payload 4 0x8b payload 5 0x9e payload 6 0x05 payload 7 0x05 In particular how long will this inquiry last and what is the maximum number of Bluetooth devices that can be found like this HINT The general inquiry access code is 0x9E8B33 see page 213 6J A function inquiry that sends an inquiry and displays the addresses of the found Bluetooth devices should look as follows Don t be confused if you are not familiar with all data types and functions they will be explained later struct btstack stack void inquiry u_char arg define a HCI command packet struct bt_hci_pkt_cmd pkt assemble the single bytes of the struct pkt see previous exercise INSERT YOUR CODE HERE INSERT YOUR CODE HERE define a command_response structure struct bt hci cmd response wcmd array for the storage of the answers of max 10 devices struct bt hci inquiry result inquiry result 10 init
100. ent to control a cell phone The topic of this tutorial covers setting up an RFCOMM connection to a cell phone and sending AT Commands to make the phone dispatch an SMS message Learning target of this tutorial is familiarizing with the Bluetooth Protocol Stack and working with standard protocols 8 2 RFCOMM Bluetooth is a wireless communication service sending in the 2 4 GHz Band It is based on a centralized network topology Nodes communicating with each other form a piconet that consists of one master and at most 7 slaves The master initiates the transmission and the slaves respond to it To achieve robustness against interference Frequency Hopping is applied Once every 0 625ms the frequency is changed Therefore transmission is partitioned into time slots of 0 625ms length Bluetooth specifies two types of transmission schemes that can be established between different devices 58 CHAPTER 8 INTERFACING TO HANDHELD DEVICES Explanation Synchronous Connection Oriented SCO The SCO link provides a circuit switched connection between the master and a single slave of the piconet The service is symmetric and requires reservation of time slots at regular intervals Therefore the master sends SCO packets at regular inter vals The specific SOC slave is allowed to respond in the subsequent time slot SOC packets are never retransmitted therefore it is an unreliable service It is mostly used for voice applications Explanation Async
101. ents that are caused by the bt con command Analyze the received ConnectionCompleteEvent to figure out if we established a synchronous SCO or asynchronous ACL connection Hint HCI events are listed starting on page 695 6 according to their Event Code Now you should be connected with another BTnode i e both radios should be synchronized in terms of slot timing frequency hopping sequence and access code to the physical channel You can check your connections with the contable command As you see a connection handle has been assigned to your connection Those handles are used to identify connections between Bluetooth devices Once a connection is established we want to send simple text messages to another BTnode 54 CHAPTER 7 COMMUNICATION USING BLUETOOTH Explanation Logical Link Control and Adaptation Protocol L2CAP The Logical Link Control and Adaptation Protocol L2CAP resides directly above the Host Controller Interface HCI At the L2CAP layer communication is based on so called channels This abstraction allows multiplexing and de multiplexing of multiple channels over a shared link Furthermore L2CAP carries out segmentation and reassembly of application data for higher protocol layers T he figure shows a L2CAP basic information frame B frame packet starting with 2 bytes for the length of the information payload Here the length indicates the size of the payload in bytes Bytes number 3 and 4 represent the channel ID T
102. er 2 Redistributions in binary form must reproduce the above copyright notice this list of conditions and the following disclaimer in the documentation and or other materials provided with the distribution 3 Neither the name of the copyright holders nor the names of contributors may be used to endorse or promote products derived from this software without specific prior written permission THIS SOFTWARE IS PROVIDED BY ETH ZURICH AND CONTRIBUTORS AS IS AND ANY EXPRESS OR IMPLIED WARRANTIES INCLUDING BUT NOT LIMITED TO THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED IN NO EVENT SHALL ETH ZURICH OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT INDIRECT INCIDENTAL SPECIAL EXEMPLARY OR CONSEQUENTIAL DAMAGES INCLUDING BUT NOT LIMITED TO PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES LOSS OF USE DATA OR PROFITS OR BUSINESS INTERRUPTION HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY WHETHER IN CONTRACT STRICT LIABILITY OR TORT INCLUDING NEGLIGENCE OR OTHERWISE ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE For additional information see http www btnode ethz ch Id ex7 6 listing c v 1 2 2007 01 17 19 21 30 yuecelm Exp 4p d dp 3E Ab EE e db OG RSD EEE EEE 1 1 o3 Log ex7 6 listing c v Revision 1 2 2007 01 17 19 21 30 yuecelm minor changes and updates after reviewing the whole tutoria
103. ered in the previous section the CC1000 is very simple you can either send a radio signal or listen for incoming signals from other nodes As there is no automatic frequency hopping as in Bluetooth we neither have discovery phases nor master slave relationships There is no default packet format or standardized access interface like HCI or L2CAP using simple commands like turn radio on and send this data we can pretty much send out anything we please However this newfound freedom also comes at a price Without the complex Bluetooth synchronization we will need to take care of limiting access to the shared broadcast medium i e the radio channel ourselves Otherwise if two or more nodes in range of each other decide to send at the same time their signals will interfere with each other this is called a collision and none of the sent data can be received Regulating access to a shared communication medium is done by a medium access control MAC layer The MAC layer is responsible for deciding who gets access to the physical layer at any one time It also detects transmission errors and provides addressing capabilities i e it verifies whether a received packet was actually intended for the receiving station BTnut comes with one particular MAC layer implementation for its Chipcon radio based on Berkeley s B MAC protocol 12 The B MAC protocol offers a very energy efficient way of regulating medium access which is espe
104. erent interrupts are used to service multiple peripherals at the same time By default interrupts are blocked while an ISR is executing thus different interrupts can block each other Therefore the careful programmer aims at keeping ISRs as short as possible Optional Exercise 3 7 Measuring the execution time of an ISR can be done as follows On a free IO pin of the ATmega128 we generate a rising edge at the begin of the ISR and a falling edge at the end The time that the IO pin is high can then be measured on an oscilloscope For example we may use pin 0 of port F which is a good choice since it is accessible as pin 6 on the 15 pin connector of the BTnode as you can verify on the B Tnode schematics Connect this pin and ground e g from pin 1 of the 15 pin connector to the oscilloscope Set up pin 0 of port F as an output pin using the DDRF register How long takes your ISR to execute How much of the processing power is thus used for sampling the battery power every two seconds HINT If you only have an analogue oscilloscope you may have to decrease the interval of the ISR drastically e g 10ms is a good value in order to display the generated waveform properly 3 5 Protecting shared data and resources In this section the program from the previous section is extended to write measured data to the terminal It is explained why this should not be done from interrupt context Thus the sampled data has to be shared by the ISR which determines
105. ers of this tutorial 2 5 First steps in BTnode programming Using the avr gcc toolchain We will now use the tools to compile and upload a first program to the BTnode Explanation ISP Programming Variants There are numerous software and hardware components that allow ISP programming of an Atmel AVR microcontroller The default tool supported by Atmel is AVR Studio which offers a graphical user interface simulation and project management capabilities To use it for programming of an AVR only open the tool and select the Program AVR entry from the Tools Menu Be sure to select the correct device ATmegal28 in the Program Tab do not change the fuse bit settings and select the right Communications Settings Auto in the Advanced Tab see figure 2 5 When continuing from the command line be sure to close AVR Studio There are numerous command line tools for ISP programming as well These are often more convenient than the GUI based tools In the following you will learn to use avrdude which also supports a GUI on windows For further informations such as using the bootloader function read the Atmel Applications Notes AVR109 Self Programming AVR910 In System Programming and AVR911 AVR Open source Programmer Exercise 2 10 Open a command line shell and check if your avr gcc toolchain is installed and working correctly First check the versions of the avr gcc toolchain by entering avr as version avr gcc v and avr ld
106. ess code GIAC The Bluetooth Controller rearranges the Inquiry command packet in such a way that the packet sent over the air begins with this GIAC Actually all transmissions over the physical channel have to begin with such an access code With the reception of a Bluetooth address we gained some knowledge that we can exploit to access the channel once more and create a connection to another device We have to pass this address as a parameter to a Create Connection command which in turn causes the Bluetooth Controller to initiate the Page procedure During this procedure the Link Manager on the Bluetooth Controller tries to establish a link level connection to another device Therefore messages beginning with a device access code DAC are generated The DAC is derived from the paged device s Bluetooth address Explanation Terminal command uartdebug The terminal command bt uartdebug 1 displays all HCI traffic on the UART Bytes starting with a w are sent to the Bluetooth Controller those starting with a r are received from the Controller Events and Commands can be interpreted as follows bytes 1 2 3 4 5 HCI command packet 1 Opcode parameterlength parameter HCI event packet 4 event code parameterlength parameter Exercise 7 5 Compile and upload the bt cmd application Type bt uartdebug 1 Start an bt inquiry and create a new connection to an arbitrary BTnode using the command bt con Identify the impinging ev
107. eturn 1 THREAD my_thread arg int count 0 if strncmp A runningThread gt td_name 1 0 NutThreadSetPriority 10 for f NutEventWait amp event NUT WAIT INFINITE count printf Thread s has received event no d n runningThread gt td_name count pause 12 t int main void 1 int count 7 init stdout NutThreadCreate A my thread 0 192 NutThreadCreate B my thread 0 192 while count gt 0 NutEventPost amp event printf main posts an event n count printf main enters endless loop n pause 12 for NutThreadYield return 0 Solution 5 14 The output received is main posts an event main posts an event main enters endless loop myThread has received event no 1 myThread receives only 1 event even though main had posted an event twice before starting myThread Thus we see that the event queue remembers that an event was posted when no one waits for it but it does not remember how many events have been posted The implementation of the event queues is so that the event queue enters the signaled state when an event is posted and nobody waits for it but there is no counter of such events Sample Code include lt stdio h gt include lt dev usartavr h gt include lt sys thread h gt include lt sys timer h gt include lt sys tracer h gt include lt sys event h gt include lt hardware btn hardware h gt include lt le
108. f avr libc by Nut OS and the BTnode specific device drivers provided by BTnut In the following we will simply call this layered OS architecture BTnut yet one should keep the differences in mind in order to better understand the overall system operation We first look at a minimal BTnut program 28 CHAPTER 4 THE BTNUT OPERATING SYSTEM Explanation A minimal BTnut program BTnut programs are written in C though we don t have access to all libraries that we are used from our PCs Just as any other C Program the feature a main function as the initial focus of control i e this is the first function that gets executed after power up of your BTnode However in contrast to regular PC programs our BTnut programs must always begin with initializing the B Inode hardware include lt hardware btn hardware h gt for btn hardware init int main void 1 ALWAYS call this func at the beginning of main btn hardware init initialize SRAM for do something clever here main should never return where to Another peculiarity of a BTnut program is that it should never actually finish In contrast to a PC program one cannot return to the command line after the execution of a particular application is done BTnodes are expected to continously execute their task If their main program ends the behavior of a BTnode is undefined it might simply restart or stop altogether or HINT Do not
109. fcomm_disconnect in the latter case Parameter of the function should be the Bluetooth address HINT Include some delay after each AT Command e g NutSleep 1000 Register this function as a terminal command HINT Registering terminal commands has been intro duced in section 4 3 Besides it is documented in the header file btn terminal h which can be looked up in the BTnut API AT Determines the presence of a phone Returns either OK or ERROR AT CGMI Request Manufacturer Identification AT CGMM Request Model Identification AT CGSN Request Product Serial Number Identification 5 Compile and upload your program Open a terminal to observe the output 8 4 SENDING AN SMS MESSAGE USING AT COMMANDS 63 8 4 Sending an SMS Message using AT Commands There are two ways to ways to send SMS messages using the AT Commands On the one hand there is the simple SMS text mode II where you can send the message as plain text 1 2 3 AT CMGF 1 Set to text mode AT CMGS lt phone number gt Send the recipient s phone number in international format ie 41 lt message gt Send the message followed by the special line delimiter defined as 1 in the ASCII code On the other hand there is the more complicated protocol data unit PDU mode Since the text mode is not supported by every phone this tutorial only focuses on the PDU mode The PDU for SMS messaging is assembled as follows 00 ZI 00 gg 91 1477 14 36 21 00 0
110. ference and find out to what ports and pins each of the three sensors the light temperature and motion sensor are connected When using any kind of sensor platform with a B Inode we thus first need to know how an individual sensor is connected to our microprocessor Analog sensors will most certainly be connected or have to be connected to one of the ADC input pins while digital ones either use TWI or are connected to a generic input pin Knowing how and where a sensor is connected we then need to understand the sensor s output ie what information is delivered from the sensor to the input pin This can be found in each sensor s datasheet Last not least we must then properly query these sensor values in our program either by simply polling a sensor value repeatedly using a timer to do this repeated polling for us or by setting an interrupt to occur whenever a sensor value changes The following sections will describe each sensor type in turn before outlining two possible ways of querying sensor values polling and interrupts 10 2 Sensor Types BTnodes support three types of sensors digital bus sensors digital logic level sensors and analog sensors Each type needs to be connected to different pins each type needs a different way to read out a value The sections below describe in detail how a generic sensor would need to be read out However for certain sensor platforms such as the B sense sensor board higher leve
111. fic programming language for dialup modems Back in the early days of Microprocessors when the Apple II was booming users had to dial the phone manually and use an acoustic coupler for modem connection Although internal modems did not have this shortage they lacked the ability of being universal since a different hardware design was needed for every computer bus A more modular approach was an external modem connected to the widely available RS232 interface It was then when Dale Heatherington came up with the trailblazing idea to develop an external modem that was able to receive commands over the RS232 data line Hence the Hayes Command Set or AT Commands were created Mobile phone manufacturers in one way or another have adopted this command set for the built in modems Those modems can be accessed via Bluetooth Infrared USB cable or RS232 cable connection Most of a cell phone s basic functionality AT Commands e g sending an SMS message are specified in 5 and standards referenced in there However there are also vendor specific commands The standard AT Command format consists of the Command itself followed by a carriage return Four different types of commands exist 14 The Set Format It is used to change settings of the mobile phone AT command parameters CR where AT notifies the built in modem that a command is being entered command the name of the command being entered parameters the values to be used by the com
112. fically the B MAC protocol uses cca c to implement the clear channel assignment while crc c provides CRC error checking Additionally cc1000_tuner c allows us to change the radio s frequency 68 CHAPTER 9 THE CHIPCON RADIO MAC layer you will only need to include both ccc h and bmac h The next three sections will explain initialization the radio sending data and receiving data includes includes includes Figure 9 1 CC1000 Modules 9 2 1 Initialization Initializing the CC1000 radio is done in the ccc init function which takes as its single argument a mac interface structure i e a reference to a MAC protocol to be used for communication Consequently we will first need to initialize our MAC library which will create a matching instance of such a mac interface structure for us The relevant code thus looks like this include lt cc bmac h gt include lt cc ccc h gt define NODE_ADDRESS 0x0000 static void init radio void 1 int res initialize bmac also fills bmac interface structure res bmac init NODE ADDRESS if res 0 bmac initialization failed halt system bmac enable led 1 res ccc init amp bmac interface if res 0 cc1000 initialization failed halt system Notice that we need to supply a node address for B MAC initialization This address will be used by the MAC layer to filter out packets addressed to other nodes i e we will only receive packets a
113. g sensor and actuators rev 1 1 1 Microchip TC74 digital IC temperature sensor 9 Taos TSL252R analog light sensor Napion AMNI digital binary motion sensor passive IR 15 Ae WwW N muRata 7BB 12 9 piezoelectric buzzer 10 backside Figure 10 1 The BTsense rev1 1 sensor board Another popular alternative for connecting sensors to the BTnode is the set of boards developed at Teco in Karlsruhe These boards have an extension connector that fits directly into the USB programming 76 CHAPTER 10 BTNODES AND SENSORS board They come in several sizes and differ in the number of sensors they offer The largest board spart additionally featured a separate microcontroller that would relieve the BTnode ATmega of any sensor related management tasks though making its usage somewhat more difficult The ssmall boards without microcontroller are available in a medium and large size and feature e Microchip TC74 digital IC temperature sensor e Taos TSL2500 analog light sensor MAX8261 OP capacitive microphone e ADXL210 2 axis acceleration sensor Second ADXL210 for combined 3 axis acceleration sensor only on full version of the board solder plates for optional pressure sensor humidity sensor second temp sensor speaker etc e Two LEDs In order to be able to gather sensor data on our BTnode we first need to understand how its processor the ATmega128L receives and processes external data and
114. gram that indicates motion detection through LED or buzzer signaling Instead of repeatedly polling the current value of the motion sensor you should use set up an interrupt service routine to get triggered whenever the motion sensor s signal changes Describe the output you observe Exercise 10 13 Extend the program from ex 10 12 above to send motion events via the radio to a receiving node which then prints out a corresponding line to the terminal Optional Exercise 10 14 Combine the motion sensors of several B Tnodes in order to be able to detect the direction of motion e g along a corridor or on both sides of a door Both nodes should send motion events to a sink node which then determines the direction of the motion and keeps an on screen statistic e g how many people entered and exited a certain room Tip In order to limit the area that the motion sensor covers you can simply build a small paper cone and put it around the sensor Optional Exercise 10 15 Write a program that periodically reads out all available sensor values and sends them wirelessly to a sink node which is connected to a laptop or PC via USB Try to save power by grouping several measurements into a single transmission The sink node should print out the comma separated list of values to STDOUT which can then be easily captured into a file by using the terminal s capture to file function and then displayed graphically in Excel OpenOffice Spreadsheet or GN Upl
115. guration onto Port C It is controlled via pin PB5 LATCH SELECT Pin Function PCO Blue LED PC1 Red LED PC2 Yellow LED PC3 Green LED PC4 ON VCC IO 5 VCC CC PC6 ON VCC BT PC7 RESET BT The first problem from this hardware setup is that the software has to keep track of the states of the latch outputs since it is impossible to inquire the current latch state at the port outputs in software The second problem is that the routine for driving the latch should not be interruptible yet it has to be short so that it does not interfere too much with other software components timing requirements Solution 2 2 Project setup in Eclipse follows the menu functions and is straightforward Solution 2 3 The indexing function is a very powerful tool within Eclipse It is much faster than global search and can discriminate definitions declarations and references Solution 2 4 The BTnut system software supports scheduling of different patterns at the LEDs a simple yet powerful user interface on embedded systems Solution 2 5 The Content Assist function is yet another powerful feature when using Eclipse It allows to quickly navigate different library functions and gives quick hints to their correct usage syntax Use it to add an additional LED pattern to a simple BTnut application btn hardware init btn led init 1 btn led add pattern BTN LED PATTERN HALF 0 10 BTN LED INF
116. h the following signature bt hci send acl pkt struct btstack stack u short con handle u char pb flag u char bc flag u short payload total length struct bt hci pkt acl pkt As you can see this function automatically sets the entries of the HCI ACL Packet header However it is still necessary to allocate memory total size for all the entries of the hci_acl_pkt packet although the first entries don t have to be specified 7 3 CREATING CONNECTIONS AND SENDING DATA PACKETS 55 Exercise 7 6 Copy the bt cmd application and add a new function called transmit Register this function as a terminal command that takes a connection handle a channel ID and a string message as arguments Define a hci acl pkt packet that allocates enough memory for a complete HCI ACL packet with an in formation payload of 20 characters and transmit it Hint You don t have to know any details about the bt hci pkt acl struct Just cast your hci acl pkt packet accordingly In order to receive short messages the following receive function has to be defined struct bt hci pkt acl receive void arg struct bt hci pkt acl pkt bt hci con handle t con handle u_char pb flag u_char bc flag u short len u long t arrive 1 u_char 12cap_hdr pkt gt payload u_char 12cap_data u_short chan_id chan id 12cap hdr 2 12cap hdr 3 lt lt 8 12cap data amp 12cap_hdr 4 printf message received on channel d s n chan id 12cap_data
117. hat the actual declaration of arg as a void pointer is done by the macro Don t forget to include lt sys thread h gt for working with threads The thread my_thread is now defined but it has to be started before it becomes active Explanation Running Threads A thread can be activated by any other thread e g by the main routine This is done using the command NutThreadCreate include lt sys thread h gt int main void if NutThreadCreate My Thread my_thread 0 192 0 Creating the thread failed for do something The first parameter defines a name for the thread the second parameter is the name of the function we have defined before The third argument is a pointer that is passed to the thread function compare with the second argument arg of the THREAD macro we do not use this feature here and thus an arbitrary value can be used The last argument is the size of the stack that is allocated for the thread This stack is used for local variables and for passing arguments when calling subroutines If this value is chosen too large the system may run out of heap memory If it is chosen too small the thread overwrites memory that is used otherwise which results in unpredictable behavior See page 30 for a method to check whether your stack size is correctly chosen For now just use 192 and you will be fine Exercise 5 1 Write a program that creates a thread as explained abo
118. he rest of the packet is reserved for the actual payload Clearly the size of the payload is limited But for the short messages we want to send in this tutorial we won t get into conflict with those payload limits L2CAP Audio Link Manager um Baseband Bluetooth Radio L2CAP B Frame Packet HCI LSB 0 16 32 Channel ID Length Information Payload HCI ACL Data Packet LSB 0 4 8 12 16 20 24 28 32 36 39 Connection Handle Flag Flag Payload Total Length Payload Also an HCI asynchronous connection oriented ACL data packet is illustrated To distinguish between HCI commands events and data packets the type parameter has to be set The packet boundary PB flag is used to indicate the first packet PB 2 or a continuing fragment packet PB 1 of a higher layer message By setting the broadcast flag BC 0 a point to point message is defined Finally the payload length again in bytes concludes the header of the HCI ACL Packet The body of the HCI ACL Packet consists of the L2CAP B Frame Packet in our example More information about L2CAP can be found in 6 on pages 963ff In the following we want to write a transmit function which sends a HCI ACL Data packet of the form u_char hci acl pkt total size hci acl pkt 1 So oes 5 hci_acl_pkt 2 hci acl pkt total size We will send this packet using the function hci send acl wit
119. heck out a release of Nut OS either by executing make nut cvs sources in the btnut directory or by checking it out from CVS into a paral lel project as described above host btnode cvs sourceforge net repositorqy cvsroot ethernut module nut The build the BTnut libraries first by executing make clean and make all in the btnut directory 18 CHAPTER 2 FIRST STEPS IN BTNODE PROGRAMMING 19 Chapter 3 Device Level Programming 3 1 Introduction The goal of this session is to familiarize the reader with some peculiarities of programming microcontrollers that have a rich set of peripherals After going through the tutorials and exercises you should be able to understand and write simple drivers which allow you to use these peripherals efficiently To work through the whole chapter takes you approximately four hours without the optional exercises about two hours In this session we will avoid using library functions and operating system support as far as possible The reason is that you should be able to really understand what is going on instead of using some black box functionality Clearly this type of programming is often a bit cumbersome But you will enjoy the comfort and convenience of an operating system that you will learn to use in the next session all the more In Section the use of off chip resources is explained using the example of the LEDs on the BTnodes In Section ed d reader learns how to use the analog digital co
120. heck these locations to learn more about development issues and possible caveats If you discover a bug either enter it into sourceforge net or post them on the BTnode mailing list Now you have gained an overview of the BTnut System Software developing in Eclipse and know how to navigate code and search for documentation 12 CHAPTER 2 FIRST STEPS IN BTNODE PROGRAMMING Explanation BTnut Configuration Options The BTnut System Software uses a GNU make based build system The basic configuration is done in a file Makerules and parameters are defined in Makedefs and can be overridden by setting them as environment variables BURN avrdude BURNPORT dev ttySO BURNFLAGS pm128 cavrispv2 P BURNPORT s Alternatively you can use uisp with the settings BURN uisp BURNPORT dev ttySO BURNFLAGS dprog stk500 dpart atmega128 dserial BURNPORT NN wr fuse e OxFF wr fuse h 0x00 wr fuse l O0xBF Defines for btnode3 platform MCU BTNODE3 atmegai28 ARCH BTNODE3 avr HWDEF BTNODES D HARVARD ARCH D__BTNODE3_ DEFS BTNODE3 HWDEF BTNODES3 further define options DEFS BTNODE3 DNUTTRACER DEFS BTNODE3 DNUTTRACER_CRITICAL DEFS BTNODE3 DNUTDEBUG DEFS BTNODE3 DNUT_PERFMON DEFS BTNODES DBT_L2CAP_SLIMDOWN DBT_RFCOMM_SLIMDOWN Here you can select parameters for the default programming interface and define debugging verbosity We will make use of these features in later chapt
121. hortpause function Calling pause 12 resulted in a pause of approximately 1 second Calling pause 12 runs the loop in shortpause 12 Oxffff 768 000 times Now we look at the list file 13 Shortpause 14 prologue frame size 0 15 prologue end size 0 16 0000 20EO ldi r18 108 0 17 0002 30E0 ldi r19 hi8 0 18 0004 2817 cp r18 r24 19 0006 3907 cpc r19 r25 20 0008 28F4 brsh L8 21 L6 22 000a 2F5F subi r18 108 1 96 APPENDIX B SOLUTIONS 23 000c 3F4F sbci r19 hi8 1 24 000e 2817 cp r18 r24 25 0010 3907 cpc r19 r25 26 0012 D8F3 brlo L6 27 L8 28 0014 0895 ret 29 epilogue frame size 0 30 epilogue noreturn 31 epilogue end size 0 32 function shortpause size 11 11 33 size Shortpause shortpause The loop is coded in the lines 21 to 26 line 21 is not an instruction thus the loop is 5 instructions long So in 1 second approximately 768 000 5 3 930 000 instructions are executed Assuming that every instruction takes one cycle results in a clock frequency of 3 9 MHz Looking at the instruction set summary in the atmega manual tells us that the brlo takes two cycles thus we get to a clock frequency of 768 000 6 Hz 4 7MHz The clock frequency is actually 7 3 MHz The error of course results from the extremely inaccurate mea surement of one second Sol inc T T def def void void void
122. hronous Connection Oriented ACL The ACL link provides a packet switched connection between master and all active slaves of a piconet A slave is only allowed to transmit an ACL packet if it has been polled by the master in the previous time slot The ACL link uses a fast acknowledgment and retransmission scheme to guarantee reliability Since no time slots are reserved for transmission this type of communication is usually used for non time critical applications Application TCP IP AT Commands PPP xmwo RFCOMM TCS SDP L2CAP HCI Audio Link Manager Protocol Baseband Bluetooth Radio Figure 8 1 The Bluetooth Protocol Stack The Logical Link Control And Adaption Protocol L2CAP has been discussed extensively in section The focus of this tutorial is on the higher level protocols and their application As explained in section the Bluetooth address is needed to establish a connection to a remote device Exercise 8 1 Find out the Bluetooth device address of your cell phone This can be done in two ways e Some manufacturers put a tag with the address printed om it on the back of the phone where the battery is inserted The address is 12 digits long hexadecimal formatted and usually indicated by the term BD ADDR e As discussed in section 7 2 Bluetooth devices cam be discovered using the Inquiry Co
123. ialize the cmd response structure wcmd ogfocf 0x01 lt lt 8 0x01 lt lt 2 wcmd cmd handle OxFFFF wcmd response 0 wcmd ptr amp inquiry result wcmd block 0 register the wcmd in the WaitQueue of the btstack bt hci setWaitQueue stack amp wcmd send the command packet bt hci send pkt stack u_char amp pkt printf Starting inquiry n wait for the inquiry to complete INSERT YOUR CODE HERE INSERT YOUR CODE HERE printf Inquiry done n print inquiry_result to the terminal INSERT YOUR CODE HERE INSERT YOUR CODE HERE 52 CHAPTER 7 COMMUNICATION USING BLUETOOTH First of all we need a pointer to a variable of struct btstack type for our function to work properly This variable stores data for numerous devices buffers and internal states We need this structure for the definition of the UART transport Furthermore the btstack structure stores a list of signatures of all uncompleted commands or more precisely list of pointers to bt hci com response structures Explanation struct bt hci cmd response struct bt hci cmd response 1 u short ogfocf u short cmd handle long response void ptr HANDLE block 3 The ogfocf is used to store the complete OpCode of the pending command Setting the cmd handle to OxFFFF indicates that this command is not referring to an open baseband connection When events return as a response to our Inquiry Comma
124. if you are lucky you would notice that sometimes strange values are printed on the terminal 3 5 PROTECTING SHARED DATA AND RESOURCES 25 Explanation Corruption of Unprotected Data If two flows of control e g the main routine and an ISR access a piece of data its value can become corrupted Assume that the ISR writes to a 16 bit variable which is read by the main routine Assume that its value at some point of time is 0x00ff Now the main routine first reads the upper byte that is 0x00 and then the ISR is executed The ISR may increment the variable to 0x0100 After the ISR has terminated the main routine continuous reading the variable and reads the lower byte as 0x00 Now the main routine has read the variable as 0x0000 which is far off the real value of either 0x00ff or 0x0100 This problem can be solved by using critical sections that is by protecting the access of a shared variable in the main routine from being interrupted by an ISR The other way round is no problem since an ISR cannot be interrupted by the main routine Explanation Enabling and Disabling Interrupts To protect a piece of code from being interrupted you can disable interrupts globally using the function cli To reenable interrupts you can use the function sei These instructions clear and set the I bit of the SREG register which is the main status register of the ATmegal128 microcontroller Exercise 3 11 Protect the shared data
125. imer is reset after a packet has been received Print corresponding ping and pong messages upon sending each packet type Watch the output of both nodes over two separate terminals occasionally reseting one node to see whether your program works in both directions Don t forget to reset the timer upon packet reception Attention CC1000 reception using battery power is extremely unreliable in the current BTnut release 1 8 This is most likely a software problem and should hopefully be fixed in future releases Until then we recommend using USB power when trying to receive data of the CC1000 9 3 Advanced Topics Two interesting features of the CC1000 radio are that both its frequency and its power output can easily be adjusted allowing for example frequency hopping schemes or minimal power transmissions 9 3 1 Power Control Transmission power can be set using the cc1000_set_RF_power function which can be found in cc1000 h It accepts a value from 0 to 255 with 0 being no power 1 being the minimal power and 255 representing maximum transmission power include lt cc cc1000 h gt void rfpower_cmd char arg 1 u short num u char num2 if sscanf arg Au amp num 1 num gt 255 1 printf usage rfpower 0 255 Wn cc1000 get RF power amp num2 printf Current RF power level is u n num2 return 6 Sending data however works fine both under battery and USB power 9 3
126. in a single shot It fills the UART buffer until it is full then yields execution to the idle thread and is woken up when the buffer has become empty again to write the rest of the output In the previous step we have seen that even when the BTnode seems to do nothing really useful several threads are executed To understand a little bit better how this actually works we now do another trace capturing in addition to the threads also the occurrence of interrupts To this purpose type trace mask es ex3 trace mask TRACEMASK 6 5 THE OS TRACER 47 0 Critical Enter OFF 1 Critical Exit OFF 2 Thread Yield ON 3 Thread SetPrio ON 4 Thread Wait ON 5 Thread Sleep ON 6 Interrupt Enter OFF 7 Interrupt Exit OFF 8 Trace Start ON 9 Trace Stop ON 10 User ON You get a numbered list of event types followed by either ON or OFF Typing trace mask 6 redisplays this list but now the event type 6 which is the begin of an interrupt service routine is set to ON Repeat this for the event type 7 Now take a trace as explained in the previous steps capture the event list in a file and display it using Matlab mainr mainr idle idle LED LED Int UARTO_TXEMPTY Int UARTO TXEMPTY ntFUARTO RXCOMPL ntFUARTO RXCOMPL nt TIMERO OVERFL nt TIMERO OVERFL 250 5 251 251 5 252 516 516 5 517 517 5 518 Time ms Time ms Figure 6 2 LED thread woken up by the timer interrupt Left LED thread woken up by the ti
127. ion call simultaneously initializes the UART to the Bluetooth radio Additonally you should include the following header files to ensure availability of all the functions and data types used so far 7 3 CREATING CONNECTIONS AND SENDING DATA PACKETS 53 include lt hardware btn hardware h gt include lt terminal btn terminal h gt include lt stdio h gt freopen include lt dev usartavr h gt NutRegisterDevice APP_UART UART_SETSPEED include lt bt bt_hci_dispatch h gt for the setWaitQueue command include lt sys event h gt for NutEventWait include lt bt bt_hci_cmds h gt Exercise 7 3 Complete the inquiry function and register the command inquiry as a terminal command Don t forget to initialize your hardware with btn hardware init and btn hardware bt on After having successfully implemented your Inquiry command find out which BTnodes you have discovered Exercise 7 4 Use the OS Tracer from Chapter 5 to trace your Inquiry command and see how the BT Stack fetches the single events You can start the tracer with trace oneshot and stop it with trace stop Read on page 532 in 6 about which event packets may arrive at the Bluetooth host and identify those events in the trace plot Hint For this you will need to temporarily disable the LED thread 7 3 Creating Connections and Sending Data Packets One of the parameters we send to the Bluetooth Controller with our Inquiry command was the general inquiry acc
128. is buggy 1 NutSleep puts the threads in the sleep queue AFTER all threads of higher or equal priority 2 When threads are woken up the threads are put in the run queue BEFORE all threads of lower or equal priority 105 Thus if two threads have the same priority and are woken up at the same time their order gets reversed The probelm does not occur when the threads have different priorities or are woken up at different times Both threads are woken up at the same time because NutSleep has a granularity of approximately 64 milliseconds We have seen in the previous chapter that a printf with such a short string takes about 1 millisecond thus both threads go to sleep and are woken up in the same 64 milliseconds time slot Sample code include lt sys thread h gt include lt sys timer h gt include lt hardware btn hardware h gt include lt led btn led h gt include lt stdio h gt freopen include lt io h gt _ioctl include lt dev usartavr h gt NutRegisterDevice APP_UART UART_SETSPEED int init_stdout void u long baud 57600 sbi PORTD 2 NutRegisterDevice amp APP_UART 0 0 freopen APP UART dev name r stdout _ioctl _fileno stdout UART SETSPEED amp baud return 1 THREAD my_thread arg NutThreadSetPriority 20 for 1 printf my thread is alive n NutSleep 1000 int main void hardware init btn_hardware_init btn_led_init 0 init_stdou
129. ization 244 9 ua dena RR e dnd 68 LIO oe oe ee ee eae eS 69 9 2 3 Receiving Data The ccc rec Receiver Thread 71 9 3 Advanced Topics 2222s 72 9 3 1 Power Control 4o b Ron so Row ee EORR E RO m SOR E Rex 72 9 3 2 Frequency 73 9 3 3 Measuring Signal Strength es 74 75 TIPP 76 Chae he T a a oe bbb hE hh ee EGS Vee Re 77 a Gem 77 cS ee ee ee ei ee 79 CIT T9 19 3 Reading Sensor Data o oko RO X OR EUR a RA 81 CONTENTS 10 3 1 Polling nm 10 3 3 Hardware Timers and Actuators 10 4 The btsense library Software Versions Used 81 81 88 86 89 91 Date Section Who Changes Mar 2 2005 jb Initial Version 0 1 Mar 24 2005 2 3 jb pb Initial drafts of 2st and 2nd exercise done Mar 30 2005 3 jb Added input from beta testers ready for distribution May 10 2005 1 6 jb cm Edits after Clemens first import added BTnode developer kit to introduction May 12 2005 all jb cm md Fixed graphics and rest of 5 and 6 prep for first release Mar 21 2006 1 jb Minor updates Mar 24 2006 1 2 appendix jb Finished chapter 1 and 2 draft for SS2006 Apr 5 2006 2 jw Added bootloader Apr 5 2006 1 2 4 appendix jb Minor changes to chapter 2 Checked all solutions and moved some files around Apr 6 2006 1 ml Added Marc
130. l Revision 1 1 2007 01 16 13 07 52 beutel first try with all new solutions and marcs stuff Revision 1 3 2006 05 19 15 02 08 cmoser79 final changes to chapter 6 Clemens Revision 1 43 2006 04 06 08 52 10 kevmarti removed log cmds register cmds function registering is now done in log_cmds_init Revision 1 42 2006 04 05 12 56 21 kevmarti adjusted call to log initO Revision 1 41 2006 04 05 12 47 37 kevmarti Added call to log cmds init Revision 1 40 2006 04 05 10 44 22 kevmarti terminal cmds for logging moved from debug logging c to terminal log cmds c Revision 1 39 2006 04 05 10 05 48 beutel empty log message Revision 1 38 2006 04 05 05 29 36 dyerm fixed reading of bt version and features for the fancy header 115 Revision 1 37 2006 03 29 01 15 00 olereinhardt Changed signedness of strings in order to compile with avr gcc 4 0 2 Revision 1 36 2006 03 24 14 44 50 dyerm removed obsolete bt acl com Revision 1 35 2006 03 23 17 13 57 beutel added version features and name to bt cmd Revision 1 34 2006 03 23 17 12 39 beutel added version features and name to bt cmd Revision 1 33 2006 03 23 07 22 24 dyerm Merged changes from multihop merge branch See individual changes on multihop merge branch See Changelog for summary of changes
131. l support is available in form of dedicated functions alleviating the need for direct manipulations of the individual ATmegal28L ports Nevertheless knowing the general principle of sensor read out should certainly foster overall understanding 10 2 1 Digital I C Bus Sensors The was originally developed by Philips Semiconductors the 1980s to simplify communication among various chips within T V sets It is a simple Master Slave bus with a 7 bit address space that supports 2 2C is pronounced i square c sometimes also i two c 78 CHAPTER 10 BTNODES AND SENSORS up to 112 slave devices 16 addresses of the possible 128 are reserved The biggest advantage of the I C protocol is its abilitiy to allow a single microcontroler the control of more than hundred devices with only two I O pins The ATmegal28L used in the BTnode supports the I C protocol in hardware which greatly simplifies control of I C compatible devices However as I C is a registered trademark of Philips Atmel calls this TWI two wire interface The two wires of the I C bus are called SDA data and SCL clock Communication is always initiated by the master and is only between the master and a single slave The clock is controlled by the master this is handled by the ATmegal28L for us it tells the slave when it should read a value from SDA i e when SCL is high P This allows the use of the I C protocol also without fixed hardware or r
132. lanation Pull ups Pull ups are resistors in an electronic circuit that ensure that given no other input a circuit assumes a default value The I C protocol requires that when IDLE i e when no devices use it the bus remains in a logic HIGH state This is achieved by inserting so called pull up resistors into the circuitry which have the effect that as soon as at least one device puts a LOW value onto the bus the whole circuit will be pulled to a logic LOW state This allows other devices to detect communication on the bus Each of the 53 I O pins of the ATmegal28L can have pull ups enabled or disabled using the PORTx register Also notice that the TwMasterTransact function references both the command variable and the result variable i e it is not just for sending a command to a TWlI compliant device but also for receiving its result Exercise 10 3 Locate the TC74 datasheet off the BTsense documentation page on the BTnode Web site and find all supported P C commands with their corresponding command codes 10 2 2 Digital Logic Level Sensors Another type of digital sensor is that of the logic level sensor While also digital it simply responds in a binary fashion logical 1 and 0 VCC and GND represent on or off detected or not detected critical or not critical Such sensors do not need and do not support special communication protocols such as I C Instead we can directly connect them t
133. le btn_cmds_register_cmds provides the led command nut_cmds_register_cmds provides the nut command which has several sub commands Hit the Tab key for a list of available commands Exercise 4 3 Incorporate the default BTnut commands into your small terminal application Use the nut threads command to show the currently running threads Now include led btn led h and add a call to btn_led_init 1 right after initialization Also add NutSleep 1000 to the final for loop so that it isn t empty this needs sys timer h Observe the output of nut threads now Exercise 4 4 Change the call to btn_terminal_run to use BIN_TERMINAL_FORK as its first parameter you can leave the second argument 0 right now and check the output of nut threads again 4 4 TIMERS 31 Explanation Creating your own Terminal Commands You can also register your own commands with btn terminal You must provide a function with a standardized interface a pointer to a single argument of type char which can then be registered under an arbitrary command name void _cmd_square char arg int val if sscanf arg 4d amp val 1 printf The square of d is 4dWMn val val val else printf USAGE square lt value gt n int main void btn terminal init stdout btn3 gt btn terminal register cmd square cmd square btn terminal run BTN TERMINAL NOFORK 0 for 33 The command square is registered with btn_ter
134. load replies will be caught by the terminal program not your upload tool i e the upload will fail int main void 1 btn hardware init initialize SRAM init_stdout int variable 13 printf Hello world printf my lucky number is d n variable for main should never return To read data from the terminal you can use the function fscanf However in order to read input from the user we can use an already defined library lt terminal btn terminal h gt which offers convenient access 30 CHAPTER 4 THE BTNUT OPERATING SYSTEM to user input Specifically through the use of btn terminal a programmer can define a set of commands and optional arguments that a user can execute from a terminal prompt Upon hitting the Tab key the BTnode terminal program lists all available commands Explanation The Interactive Terminal The BTnode terminal is defined in terminal btn terminal h After initializing it with the stream to use and prompt to display the programmer simply has to run it include lt hardware btn hardware h gt include lt dev usartavr h gt NutRegisterDevice APP_UART UART_SETSPEED include lt terminal btn terminal h gt for interactive terminal includes stdio h and thus io h int main void btn_hardware_init init stdout as defined above btn terminal init stdout btn3 gt printf NnHowdy Nn btn terminal run BTN TERMINAL NOFORK 0
135. ls namely a BTnode the USB programming adapter and a USB cable For a complete listing of software tools and their respective versions used in this tutorial please see ap pendix A The tutorial assumes that the necessary development tools avr gcc toolchain avr libc an ISP programming utility if you use the ISP programmer Eclipse and CDT are installed and working correctly For details on the installation and configuration of the suggested development tools see the BTnode online resources available at http www btnode ethz ch Figure 1 3 The BTnode CDROM 1 4 Reference Documents Should you ever need more information than what is given here in this tutorial feel free to browse the following sites for details on the individual pieces of the puzzle e The BTnode platform reference with support documents installation instructions for the devel opment tools and source software mailing lists and various links 5 ttp www btnode ethz ch H e The home of Nut OS the BTnut operating system core ttp www ethernut de e Open source development tools for the AVR platform ttp www openavr com e Open source tools for the development on Atmel AVR Windows platform installer ttp winavr sourceforge net gt tmel AVR product family ttp www atmel com products avr gt e Atmel AVR related developer information application notes links and tools ttp www avrfreaks
136. lude lt sys timer h gt include lt sys tracer h gt include lt hardware btn hardware h gt include lt sys osdebug h gt include lt terminal btn terminal h gt int init_stdout void f u long baud 57600 sbi PORTD 2 NutRegisterDevice amp APP_UART 0 0 freopen APP UART dev name r stdout _ioctl _fileno stdout UART SETSPEED amp baud return 1 I THREAD my_thread arg int sleeptime int arg for f printf s is alive will sleep for d seconds n runningThread gt td_name sleeptime NutSleep u long 1000 sleeptime void create u_char arg static int sleeptime 1 char name 20 int val val sscanf arg s name if val 1 printf Create a thread with name s and sleeptime d n name sleeptime if 0 NutThreadCreate name my_thread amp sleeptime 292 printf FAILED n 107 else printf SUCCESFUL Nn sleeptimet int main void T hardware init btn_hardware_init init_stdout btn terminal init stdout bt cmd btnode btn terminal register cmd create create btn terminal run BTN TERMINAL NOFORK 0 return 0 Solution 5 9 include lt stdio h gt include lt dev usartavr h gt include lt sys thread h gt include lt sys timer h gt include lt sys tracer h gt include lt hardware btn hardware h gt include lt sys osdebug h gt include lt terminal nut cmds h gt include lt
137. m Software Resources 2 5 First steps in B Tnode programming Using the avr gec toolchain 12 ON DDB 0 u c QC 3 Device Level Programming 19 3 1 Introduction a dae ee a hw ovd ORE ew on 30 30 a a m P e 19 e a 19 Cn 21 22 Lunes baba eee MN 23 4 The BTnut Operating System 27 41 Introductions 0 5 s ee ee ee N ae eo 78 8 91 D RR ORO OR YN 27 4 2 Anatomy of a BTnut 27 4 3 The Terminal 4 4 Timers 4 5 Dynamic Memory Management iv CONTENTS 33 33 TIT 33 5 9 lhiread Control i une ae a uox m m RO ee od 35 5 4 Sharing Resources Mutual Exclusion Mutex 37 5 5 Events eed od ce a ox Romse ew d 3 39 6 Embedded Debugging 41 ee PEPER os kx E ub bone ey bee OAS deos 41 6 2 8 RSE dem EES OS OR en 41 TC 42 u IPLE 43 69 THEOS 2065 yale eek aa S ee S 44 7 Communication Using Bluetooth 49 TOTEM EM 49 eee he de gags Bote ee ee eS 49 T TT 53 57 ee ee ee ar a ee U 57 Deb ee ee ah 57 8 3 AT Commands s emo ye ROS a ae ei 60 TIT 63 67 RUNE eM ain ENGNG chr Uh TS ie we P cate at et 67 9 2 Accessing 1000 67 9 21 Initial
138. macro e g PRINTF Using a macro should simplify argument handling as gcc supports so called variadic macros define PRINTF acquire mutex printf __VA_ARGS__ release mutex 5 5 EVENTS 39 5 5 Events Another important part of a multithreaded OS is communication between threads This allows the coordinated use of multiple processes as threads can signal other threads when to wake up or in general inform a number of threads that they have finished processing a particular data structure Explanation Sending and Receiving Events The coordination synchronization of threads can be done using BTnut events Consider the example shown below include lt sys event h gt HANDLE my_event THREAD thread_A arg for 4 some code NutEventWait amp my event NUT WAIT INFINITE some code THREAD thread_B arg for some code NutEventPost amp my_event some code Here we see two threads Thread thread_A executes some code and then blocks in the NutEventWait function It only continues when either an event is posted or the timeout expires The timeout is specified in milliseconds with the second parameter In the example shown above the timeout is disabled i e an infinite time is specified with the macro NUT_WAIT_INFINITE Exercise 5 12 Write a program with three threads main and two additional threads and a global variable with initial valu
139. mand CR the carriage return Nr The Execute Format It is similar to the Set Format but the Execute Format usually does not require any parameters and is used to obtain information about the mobile phone The Read Format It is used to read current settings AT command CR Command Help Checks whether the command is available and returns the range of the parameters AT command CR However some commands such as the send SMS command require a special line delimiter As mentioned in the explanation AT Commands can be treated just like data packets that have to be sent over an RFCOMM channel Therefore the following function can be used Explanation bt rfcomm send u_char bt rfcomm send u_char dlci u_char data u short length This function sends data over an existing RFCOMM channel It expects the connection handle dlci the data packet and its length as arguments and returns 0x00 if the sending process was successful Exercise 8 3 The goal of this exercise is to send some basic AT Commands from a BTnode to a cell phone 1 Create a new source file and insert the contents of the rfcomm cmd application that you used in the previous exercise command registration function calls at the end of the file as they won t be needed 62 CHAPTER 8 INTERFACING TO HANDHELD DEVICES Also delete the three command initialization function calls bt 12 and rfcommo located just above the regi
140. mbedded target There are many other tools that can make life easier when projects are getting larger and debugging more difficult The selection of tools introduced here should provide you with a basic overview and understanding to define the right set of tools for your personal project needs 2 2 1 Compilation The tools introduced here are freely available and are based on GNU GCC and the AVR libe which is a Free Software project whose goal is to provide a high quality C library for use with GCC on Atmel AVR microcontrollers Together avr binutils avr gcc and avr libc form the heart of the Free Software toolchain for the Atmel AVR microcontrollers They are further accompanied by projects for in system programming software uisp avrdude simulation simulavr and debugging avr gdb avr insight AVaRICE These tools are available packaged as a Windows installer in the WinAVR project which we will use as a reference There are numerous other distributions of the avr gcc toolchain available as well as different commercial compilers for the Atmel AVR family A thorough introduction to the internals of such a compiler toolchain as used in embedded systems can be found in Appendix A Assemblers Linkers and the SPM Simulator of 7 Manuals for the avr binutils avr gcc and avr libe are packaged with the respective distribution or available online see section 1 4 The following example illustrates a sample compilation linkage with startup co
141. mer interrupt Right Main thread woken up by UART receive interrupt causing transmit complete interrupts by echoing the terminal input Looking at Fig left side you can see how the LED thread is triggered by the timer interrupt Int TIMERO OVERFLJ On the right side of Fig it is shown that the main thread is activated after the occurrence of UART receive interrupt Int UARTO TXCOMPL Since the main thread echoes all received characters to the terminal two UART transmit complete interrupts occur immediately after the activation of the main thread Exercise 6 7 The traces captured in the previous example show that most of the time is spent in a thread called idle which was not started by our program What is the purpose of this thread Exercise 6 8 When the tracing of interrupts is enabled you can see timer interrupts You can also see that a thread that sleeps always awakes immediately after these timer interrupts Figure out the interval of these timer interrupts and think about what kind of restriction this implies for the NutSleep function HINT Remember that you can specify the sleep time in milliseconds 48 CHAPTER 6 EMBEDDED DEBUGGING Explanation Tracing a Particular Piece of Code The interactive mode of the tracer tool is very simple to use but it does not allow to trace a particular piece of code in which you are interested To do this it has to be used in a different way You may be interested in what a particul
142. minal_register_cmd after the initialization of the ter minal The first parameter is the string you will have to type to launch the function whose identifier is given as the second argument Note that functions that you want to register as a commands must have the signature void lt functionname gt char arg Exercise 4 5 Write a program that registers the command echo which simply echos all the given arguments Optional Exercise 4 6 Write a program that registers the commands myset and myclear which will take the numbers 0 3 as an argument and set or clear the given LED 4 4 Timers Explanation Timers in BTnut Instead of using for loops or NutSleep calls you can also use one or more timers to schedule recurring function calls Using timers you can easily parallelize your program without the need for explicit thread management simply create a function for each required aspect of your program and register different timers for each of them BTnut will then take care of calling these functions in the given intervals include lt hardware btn hardware h gt include lt sys timer h gt HANDLE hTimer static void tm callback HANDLE h void a int main void 1 btn hardware init hTimer NutTimerStart 3000 tm callback NULL O for NutSleep 1000 never end You can use NutTimerStart and NutTimerStop to install or remove periodic timers Using TM_ONESHOT as the last parameter to Nut
143. mmand The application bt cmd located in the folder app bt cmd provides all the necessary terminal commands to determine a device s Bluetooth address 1 Compile and burn the file bt cmd c 2 Turn om the Bluetooth radio of your cell phone and make the phone traceable The two settings usually have to be turned on separately since this is a security mechanism to hide the phone s Bluetooth address 3 Open a terminal and start an inquiry This will give you a couple of Bluetooth addresses 8 2 RFCOMM 59 4 Now you need to find out which address belongs to your phone Use the command bt rname to read the name of a remote device You can edit the name of your phone in the phone s Bluetooth setup The way to do that depends on the phone s menu navigation Some phones provide a separate menu item for Bluetooth others include it in Setup gt Bluetooth or Connections gt Bluetooth or a combination of them Setup gt Connections gt Bluetooth or even differently Explanation Radio Frequency Communication RFCOMM RFCOMM is a simple transport pro tocol that emulates a serial interface RS232 over an L2CAP link Up to 60 simultaneous connections between two Bluetooth devices are supported Explanation Pairing Pairing is a security mechanism built into Bluetooth to prevent unauthorized connections At the first connection attempt connection keys of 128bit length are generated out of the Bluetooth addresses of the devices and som
144. mp killqueue 125 Can you still terminate a thread with your kill command Why Search the BTnut API for answers 40 CHAPTER 5 PROGRAMMING WITH THREADS Explanation Events Signaling in Nut OS When a signal is posted to an event queue e g us ing NutEventPost Nut OS checks to see if any thread is waiting for a signal on this queue using NutEventWait If there are threads waiting Nut OS takes the first thread only i e the one with the highest priority and sets its status from SLEEPING to READY Since posting events with NutEventPost implies a NutThreadYield the posting thread will also become READY Depending on the priority of the available ready to run threads Nut OS might continue with the posting thread switch to the signaled thread i e the one that was waiting or even execute a completely different ready to run thread with an even higher priority than those two If you want to wake up all threads waiting on a particular queue not just the one with the highest priority you can use NutEventBroadcast instead Explanation Asynchronous Events When a thread posts a signal to a particular event queue using NutEventPost or NutEventBroadcast Nut OS might switch control to another thread as these two func tion calls also imply a Nut ThreadYield and thus a switch from the RUNNING state to the READY state In order to continue running a thread may use so called asynchronous variants of those two functions NutEven
145. ms Why are function such as tan present but simple multiply and divide operations are missing How would you implement a fixed point division or even floating point operations for the AVR In addition check the FAQ found in the avr libc Manual Related Pages documentation especially entry 2 and the General Utilities Module of the avr libc Manual for information on further functions like div qsort and rand Are there other libraries and languages available for the AVR family Search for possible solutions on the web Optional Exercise 2 8 When linking an application for a microcontroller a startup or initialization code needs to be integrated that controls the bootup and initialization procedure and sets the system into a de fault state after power on This behavior can be specifically controlled by a memory map and init sections For an introductory documentation of the most common compiler flags and build steps read through the Demo Projects Module in the avr libc Manual This topic is very complex So we will generally use a pre configured set up from the BTnut build system to integrate the hardware dependant correct startup code and memory map Optional Exercise 2 9 In addition to the ChangeLog and README files provided with the BTnut System Software the project management environment on http sourceforge net projects btnode has a Tracker and Tasks section to track bugs requests for enhancements RFEs support requests etc C
146. ncreasingly hard to find After the chapters on the basics about BTnodes and operating systems the remainder of the tutorial is devoted to wireless sensor network application building using basic Bluetooth communication chapter 7 Communication Using Bluetooth more advanced Blutooth communication with mobile phones in chapter 8 Interfacing to Handheld Devices and the usage of the The Chipcon Radio in chapter 9 A short overview regarding BTnodes and Sensors is given in chapter 10 where you learn how to use the generic extension interface of the BTnode to attach simple sensor boards and use them in BTnut applications Chapter 2 First Steps in BInode Programming 2 1 Introduction In this chapter we will step you through the basic knowledge about development tools software structure and reference documentation necessary to start developing your own applications on the BTnode platform This is explained using a pre configured toolchain setup on Windows although other host platforms and tool setups are possible too Linux and MacOS X For detailed instructions on the tool installation please refer to the online documentation and links listed under section I 4 and the software versions listed in appendix A 2 2 Development Tools For basic software development you will need an editor a compiler assembler linker toolchain a standard library and an in system programming software to upload the compiled program to your e
147. ncy When setting the OCx pins as output pins using the corresponding port s DDRx register one can easily connect a waveform output to a peripheral device such as a buzzer or a motor The OCx pins can be used in three different modes CTC Fast PWM and Phase Correct PWM In the already mentioned CTC mode the OCx pin can be set to simply alternate toggle between 0 and 1 whenever the TOP values is reached see figure 10 3 below In Fast PWM mode the counter always counts from BOTTOM to MAX The 0Cx pin is cleared whenever the TOP value is reached and set when the counter begins again at BOTTOM This ensures PWM signals with constant periods i e from BOTTOM to TOP that have a pulse width of exactly TOP see figure below Phase correct PWM finally creates the high pulse of the PWM signal 6Further counter modes can be found in the corresponding chapter of the ATmegal28L manual I The exact processor speed can be obtained by calling u_long NutGetCpuClock void The two 8 bit counters 0 and 2 have only one such pin 0 0 and 0C2 respectively while the 16 bit counters 1 and 3 feature three such pins 1 OC1B OC1C and OC3C 9PWM stands for Pulse Width Modulation 10 3 READING SENSOR DATA 85 always in the center of the period not at its beginning flank by counting from BOTTOM to TOP and back again and inverting the signal when reaching TOP both upwards and downwards see figure below Wh
148. nd the number of found devices will be stored in the component long response The addresses of the found devices together with several other values will be stored at the location where the void ptr is pointing To indicate that our results are available the HANDLE block will be SIGNALED Explanation struct inquiry result struct bt hci inquiry result 1 bt addr t bdaddr u_char page scan rep mode 4 u_char page scan period mode 4 u long cod u short clock offset short rssi 1 This struct stores all the collected data of one single discovered Bluetooth device We are only interested in the bt t component As you already found out the bt_addr_t type is equivalent to a u_char 6 So we only send the Inquiry with the bt hci send pkt function pass an address to bt hci setWaitQueue function and the result will be automatically stored in our prepared variables Who is receiving and handling all the incoming events from the Bluetooth radio Answer the work is done by a THREAD called BT Stack This THREAD e invokes a blocking bt hci get pkt function searches for a matching struct bt hci cmd response if an event arrives e dumps the payload of the event correctly e invokes a EventPostAsync for the respective HANDLE e performs a final NutThreadYield You should create the BTStack THREAD in your main program by calling stack bt hci init amp BT UART This funct
149. nter value to 0 3 2 3 0xfffff 0x2164 after every overflow thus at the end of the timer interrupt routine TCCR3B 1 lt lt CS32 ETIMSK 1 lt lt TOIE3 while 1 while adc done 0 pause 1 printf Battery voltage is 4d unitsW battery voltage adc done 0 return 0 Solution 3 10 There are a few different cases to consider here battery voltage millivolt 3300 battery voltage raw 512 This does not work in my case battery voltage raw is 380 units thus 3300 380 1254000 is far larger than what can be put in an int 16 bit with a maximal value of 32767 Signed int is no better the maximum is 65535 In contrast a signed long overflows at 2147483647 which is sufficient for this case 102 APPENDIX B SOLUTIONS battery voltage millivolt 3300 battery voltage raw 512 This also does not work because 380 512 0 its integers Here is the final solution int battery voltage raw battery voltage millivolt battery voltage millivolt 3300 long battery voltage raw 512 Solution 3 11 include lt hardware btn hardware h gt include lt dev irqreg h gt include lt stdio h gt freopen include lt io h gt _ioctl include lt dev usartavr h gt NutRegisterDevice APP_UART UART_SETSPEED include lt sys timer h gt COMPUTE ADC values corresponding to 1 and 2 Volts If battery voltage is 1V the BAT_SENSE signal is 0 5V The reference voltage is 3 3V and co
150. nut app bootloader folder Compile the bootloader by executing make btnode3 You should now have a file called bootloader btnode3 hex Optional Exercise 2 14 An alternative to using the ISP programmer is using a bootloader on the BT node that can emulate ISP behaviour The bootloader may or may not be installed on your BTnode but can be built from source code and installed using the method introduced in the previous exercise See the explanation box below for more information Now to upload the program code 1 press and hold the reset button on the BTnode 2 execute the upload command below avrdude pm128 cavrisp P dev ttySO D s U flash w bt cmd btnode3 hex i 3 release the reset button on the BTnode If you can t find the reset button see figure 2 7 If you get strange error messages while programming try to disconnect and reconnect the USB cable 2 5 FIRST STEPS IN BTNODE PROGRAMMING USING THE AVR GCC TOOLCHAIN 15 Figure 2 7 B Inode reset button Exercise 2 15 Erase the bt cmd application on the BTnode Open a terminal programm to the serial port you have connected your usbprog board with 57 6k 8N1 no handshake to observe the terminal output from the BTnode Upload the simple application uart echo btnode3 hex with uart output to the BTnode As soon as the uart echo application responds you can type and see the response on the LEDs This time use the auto erase function and auto verify om avrdude av
151. nverter of the ATmegal28 as an example for an on chip resource In Section 3 4 we introduce interrupts The final Section B 5 deals with critical sections that are required to protect shared data 3 2 Off chip resource Setting and Clearing LEDs As a first example we now use the LEDs on the BTnode The reason for this choice is that for any further work with the BTnodes we need some kind of feedback from the programs we implement The LEDs are an off chip resource Unfortunately accessing the LEDs is a bit tricky and requires some hacks which are explained in the following The address bus of the ATmegal28 is 16 bit wide and it is mapped to the ports A lower 8 bits and C upper 8 bits The address bus is mainly needed to access the external SRAM AMIC 1 6252048 but at the same time it is also connected to the LEDs via a latch To set or clear LEDs the bits that determine whether the LEDs should be on or off have to be put on the address bus Then the latch is enabled i e it samples the value on the address bus After a while the latch is disabled i e it holds the previously samples value The following function does exactly this void write led u char value volatile u char pointer u_char dummy compute the pseudo address that contains the values for the LEDs pointer u_char u short value lt lt 8 force the compiler to write this pseudo address to the address bus dummy pointer now enabl
152. o one of the available I O pins of the ATmegal28L configure the corresponding port pin as input using the DDRx register cf section 10 1 and read its value from the PINx register Explanation Reading logic level data in BTnut Knowing to which pin a particular binary input is connected we can easily define this pin as an input pin and read out its value BTnut offers the setbit and clearbit functions sbi and cbi that set and clear individual bits of a selected register respectively BTnut contains macros for all ATmegal28L ports and pins allowing for a convenient way of setting or clearing individual bits in a register These macros are identical to the identifiers given in the ATmegal128L reference manual 1 see page 364 for an overview of all registers and pins define pin 5 of port B as an input pin in port B s DDR register cbi DDRB DDB5 0 means input pin read out all 8 pins of port B u_char current value port b PORTB if PORTB amp 1 lt lt PB5 pin 5 is set In many situations it is important not simply to know a logic level sensor s current value but instead to know when it changes The ATmegal28L offers various interrupts that can be configured to observe an input pin for change and trigger a program interruption whenever the output of such a logic level sensor changes More about such interrupts can be found in section 10 3 2 below Exercise 10 4 Write a prog
153. oader has been installed See exercise 2 14 for further information 2 2 5 Documentation Tools The primary source for information for any hard or software system are its manuals typically accompanied by release information changelogs readme file and known errata The internet is a general resource for developers and project management More specific mailing lists and archives offer discussion forums on specific topics such as the avr libc library usage and development or on BTnode specific issues Large online project management such as http www sourceforge net offer many services such as electronic bug tracking systems version control web visualization nightly builds software distribution and general project management Single projects typically extract documentation from source code This can be done by tools such as javadoc or doxygen to automatically generate up to date online documentation 2 3 NOTES ON THE BTNODE HARDWARE ARCHITECTURE 7 2 3 Notes on the BTnode Hardware Architecture GPIO Analog Serial lO Low power Radio ATmega128L Microcontroller Bluetooth mn oa Power Supply System Figure 2 1 BTnode rev3 hardware overview System Core The BTnode System Core consists of an Atmel ATmegal128l microcontroller clocks and SRAM memory e Atmel ATmegal28l 4 kB EEPROM 64 kB SRAM 128 kB Flash e System clock 32 kHz real time clock and 7 3728 MHz system clock e 5 processor power modes
154. od 8 bit 1Byte else NULL Using this coding scheme on the message Greetings from the BTnode should result in the Byte stream shown in the example 64 CHAPTER 8 INTERFACING TO HANDHELD DEVICES The PDU is of type string i e address lengths for example have to be converted to hex strings The message is sent in PDU mode using the following commands 1 AT CMGF 0 2 AT CMGS lt PDU length Set to PDU mode set by default Number of Bytes of the PDU minus one since the leading 0x00 does not count In the example it were AT CMGS 36 3 lt PDU gt Ox1A in the ASCII code Send the PDU followed by the special line delimiter defined as Optional Exercise 8 4 In this exercise you are asked to implement the coding of the message as specified in the PDU mode It is a difficult exercise However such problems quite commonly have to be solved in embedded programming in order to comply with the different interfaces Since this implementation is needed in the next exercise a sample solution is provided below Add another function to your source file that implements the 7 to 8 bit ASCII encoding It should take the message string and a pointer to an allocated array for the encoded string as input parameters int character_value char character const char alphabet 128 50 5 r Q Q 07 8 7 SEE LEM up 20 OR z123 a2 5 237 s 2527 AT B C D
155. ogramming exercises of chapter 7 ude lt stdio h gt ude lt string h gt ude lt io h gt ude lt stdlib h gt ude lt dev usart h gt ude lt dev usartavr h gt ude lt bt bt_hci_cmds h gt ude lt bt bt_12cap h gt ude lt bt bt_rfcomm h gt ude lt terminal btn terminal h gt ude lt terminal btn cmds h gt ude lt terminal bt cmds h gt ude lt terminal nut cmds h gt ude lt terminal 12cap cmds h gt ude lt terminal rfcomm cmds h gt ude lt led btn led h gt ude lt hardware btn hardware h gt ude lt sys timer h gt ude lt string h gt ude lt stdio h gt ude lt debug toolbox h gt ude program_version h ine BT_L2CAP_HCI_PACKET_TYPE BT_HCI_PACKET_TYPE_DM1 BT_HCI_PACKET_TYPE_DH1 BT_HCI_PACKET_TYPE_DM3 BT_HCI_PACKET_TYPE_DH3 uart terminal ct btstack stack ct bt l2cap stack 12cap_stack ct bt rfcomm stack rfcomm stack 118 APPENDIX B SOLUTIONS define MIN CREDITS 10 define MAX CREDITS 40 void rcv cb u char dlci u_char payload u short len void arg 1 u short idx if len gt 0 printf n for idx 0 idx lt len idx printf c payload idx t void con cb u char dici u_char type void arg 1 if type BT RFCOMM CONNECT printf RFCOMM Connect on dlci d n dlci bt rfcomm send credits dlci MAX CREDITS BT RFCOMM DEF CREDITS else printf RFCOMM Disconnect on dlci d n dlci void line_cb u_char dlci u_char flags voi
156. oller and Bluetooth radio is explained As an example we take a closer look at the inquiry procedure used to discover other nearby Bluetooth devices In Section 7 3 you will create wireless connections to other B Tnodes and transmit short text messages 7 2 Discovery of Bluetooth devices The Atmegal28 microcontroller communicates with the Zeevo ZV4002 Bluetooth radio according to the principles defined in the Host Controller Interface Functional Specification 6 In the following we want to send an Inquiry Command to the Bluetooth controller This command will cause the radio to enter inquiry mode and search for possible Bluetooth devices within communication range The controller will count the total number of responding devices and collect a set of values for every single device The value we are especially interested in is the Bluetooth device address of a discovered B Tnode 1 We don t refer to the page numbers printed on the original document since they are not unique 50 CHAPTER 7 COMMUNICATION USING BLUETOOTH Explanation Host Controller Interface HCT As depicted the Host Controller Interface defines sig naling and data exchange between the so called Bluetooth host and the Bluetooth controller The Bluetooth host can be seen as the microcontroller running the B Tnut system software and driving the NutOS UART driver The Bluetooth controller is physically connected to the host system via the UART The Bluetooth controller i
157. ot Optional Exercise 10 16 Extend the program from 10 15 to work with multiple BTnodes i e prefix each nodes measurements with a node ID Try to minimize packet loss e g by sending packets repeatedly Use this setup to record one or two rooms over the course of an entire day Prepare corresponding graphical plots 88 CHAPTER 10 BTNODES AND SENSORS 89 Appendix A Software Versions Used The BTnode tutorial is known to work with the following software versions AVR Studio 4 v4128P1 build462 Silabs CP2101 USB to UART Bridge 20050102 WinAVR 20060125 doxygen 1 4 6 Java 2 SDK 1 5 0 06 RXTX 2 0 T7prei javax_comm 2_0_3 solsparc eclipse 3 1 2 org eclipse cdt sdk 3 0 2 easyshell 1 2 0 ZOC Terminal 5 0 6 Emacs 21 2 Matlab 7 1r14 90 APPENDIX A SOFTWARE VERSIONS USED 91 Appendix B Solutions Solution 2 1 The external memory is connected to Port A address and data bus and Port C address bus as well as to three pins of Port G that are assigned WR RD and ALE functions A trandparent D type latch is used to multiplex Port A in order to save IO space at the cost of longer access times The BTnode rev3 further uses two pins of Port B PB7 and PB6 to bank switch 4 banks of 60 kbytes external memory the processor can only make use of one bank at a time The LED power latch is attached to Port C This allows to multiplex the address bus and the latch used for the LEDs and power radio confi
158. ouble length 1 i sum 0x01 lt lt length 1 i return sum void process message char message str char message char buffer 8 0 int length int i int character 1 char base 8 0 119 char 8 0 char rdbuffer 8 0 init message str 0 0 length strlen message if length lt 15 strcat message_str 00000 else if length gt 160 length 160 strcat message_str 0000 itoa length buffer 16 convert integer to hex string strcat message str buffer for i 0 i lt length i if i length if base 0 0 character bin2int base itoa character base 16 if strlen base 1 base 1 base 0 base 0 0 base 2 0 Strcat message str base break character character value message i if character 1 strcpy buffer 0000000 itoa character rdbuffer 2 strcpy buffer 7 strlen rdbuffer rdbuffer if i 0 amp amp i48 0 strncpy carry buffer 7 i 8 1 8 1 78 0 strcat carry base character bin2int carry itoa character carry 16 if strlen carry 1 carry 1 carry 0 carry 0 0 carry 2 0 Strcat message str carry strncpy base buffer 7 1 8 base 7 i 8 0 elset strcpy base buffer I elset ERROR Not a valid character char process_phone_number cha
159. owerful tool that allows C indexing project management integration of a make build environment debugging version control and much more Version control such as with CVS Concurrent Version System or Subversion is helpful for keeping track of changes and sharing source code among team members 2 2 4 Embedded Target Connection The software on an embedded system is typically programmed once during manufacturing onto a resident internal memory from where it is then executed Software changes are frequent during development but infrequent during the lifetime of a product For uploading code to the flash memory of the ATmegal28l in system programming a serial uploader software uisp avrdude uploader tools in AVR Studio and an appropriate programmer hardware is necessary Although basic debugging can be performed via general purpose IOs and LEDs verbose terminal output is generally preferred For this a RS 232C serial connection is necessary between the embedded target BTnode and a PC This can be done using a serial level shifter e g Maxim MAX3232 or a USB serial converter e g Silabs CP2101 In addition to uploading code using in system programming as described above the ATmegal28l features a bootloader section as well as JTAG uploading and debugging support see chapter 6 for further information on JTAG The bootloader section in the flash memory can be used to re program the user section of the flash memory once such a bootl
160. p Note that before configuring the ADC it should be turned off i e the ADEN bit in ADCSRA should be cleared After starting a single conversion the result is written to two registers ADCL and ADCH In order to know when the conversion is finished and these values can be read one can simply check the value of the ADSC bit in the ADCSRA register as soon as it is cleared the result of the single conversion can be read Alternatively one can setup an ISR for the ADC interrupt sig ADC see table below or wait for its corresponding flag ADIF in the ADCSRA register to be set The default setup will put the LSB into ADCL and bits 8 and 9 into ADCH cbi ADCSRA ADEN disable ADC ADCSRA 0 stop ADC amp conv no free runn no irq def prescaler ADMUX 0 AREF ADLAR cleared ADCO input sbi ADCSRA ADEN enable ADC sbi ADCSRA ADSC start single conversion wait until conversion is finished while bit_is_set ADCSRA ADSC find result in ADCL and ADCH NutEnterCritical result ADCL ADCH lt lt 8 NutExitCritical Note that its is important that reading out the final value is not temporarily suspended by a system interrupt see more on interrupts in section 10 3 2 below otherwise we might get a skewed result Exercise 10 5 Use the above skeleton code to write a program reading out the BTsense board s light sensor if you do not know to which port it is connected see ex above In
161. p using Matlab Thus start Matlab now Type Show trace the filename of the captured terminal output which opens a figure like the one shown in Fig 6 1 Be sure to use a separate log file for each trace captured In this figure you can see time on z axis and three threads on the y axis LED 0 2000 4000 6000 8000 10000 12000 14000 Time ms Figure 6 1 Execution of threads for the program listed in Exercise What you can see is that the BTnode spends most of the time in the idle thread Periodically it switches to the LED thread and a few times the main thread was active The LED thread is responsible for the periodic blinking of the LEDs it becomes active approximately every 60ms and takes about 300us to execute The main thread is responsible for capturing terminal input and launching the corresponding commands Thus if you did not type trace while the buffer was filling you will see only one spike to the main line at the very beginning of the trace Otherwise as shown in Fig you can see a spike for every letter of trace plus one when you pressed return Parsing a keystroke takes about 600us executing the command after pressing enter takes much longer approximately 6ms When looking closely at the last spike you may note that it actually consists of several spikes This is due to the fact that the trace command prints the status of the trace buffer to the terminal but cannot do so
162. pages unix to get detailed online help Exercise 2 12 Now connect a B Tnode to your PC using a usbprog board and USB cable see figure 2 6 Further connect an Atmel ATAVRISP programmer to the usbprog board and to a serial port on your PC The default settings are dev ttySO for programming through an ATAVRISP and dev ttyUSBO for debug ging through the serial port of the BTnode If in doubt about the right serial port for debugging use the List USB2UART script om windows or check var log messages on linuz Try to communicate with the ATAVRISP and the ATmega128l on the B Tnode avrdude pm128 cavrispv2 P dev ttySO Explanation Using the USB UART adapter board The usbprog rev2 board is used for a breakout of all pins available on connector J1 Furthermore it contains a USB to UART converter Silabs CP2101 that is used to connect the debug UART of the ATmegal28l to a PC default usage A dedicated connector for ISP programming is also available on the usbprog board Also when using the USB connection the B Tnode is remotely powered from the PC to save battery power Be sure to orient the usbprog board correctly as shown in figure The board goes above the power switch of the BTnode with the two mounting holes matching those on the BTnode If in doubt about the right serial port for debugging use the List USB2UART script on windows or check var log messages on linux Exercise 2 13 Now upload a first pre compiled appli
163. pare sig OVERFLOWO Timer 0 overflow sig OVERFLOW1 Timer 1 overflow sig OVERFLOW2 Timer 2 overflow sig OVERFLOWS3 Timer 3 overflow sig UARTO RECV UARTO receive complete sig UARTI RECV UARTI receive complete sig UARTO TRANS UARTO transmit complete sig UARTI TRANS UARTI transmit complete sig UARTO DATA UARTO data register empty sig UARTI DATA UARTI data register empty Table 10 2 Selected BTnut interrupt signals NutEnterCritical saves the current interrupt state before disabling them so that NutExitCritical can restore whatever state previously existed If interrupts were disabled before calling NutEnterCritical they still stay disabled even after calling NutExitCritical 10 3 3 Hardware Timers and Actuators While adequate for issuing periodic sensor readings the use of NutTimerStart has two important drawbacks it only has a resolution of milliseconds and actual code execution is thread based i e it might be delayed potentially indefinitely due to higher priority threads or non yielding threads In order to use more real time and fine grained timers the integrated hardware timers of the ATmegal28L can be used directly This becomes important when driving actuators e g the buzzer of the BTsense sensor board or controlling motors based on pulse width modulation PWM The ATmegal28L processor features two 8 bit and two 16 bit timers Timer0 and Timer2 and
164. pecify connection port F Override invalid signature check e Perform a chip erase U lt memtype gt r wlv lt filename gt format Memory operation specification Multiple U options are allowed each request is performed in the order specified n Do not write anything to the device V Do not verify u Disable safemode default when running from a script s Silent safemode operation will not ask you if fuses should be changed back t Enter terminal mode E lt exitspec gt lt exitspec gt List programmer exit specifications y Count erase cycles in EEPROM Y number Initialize erase cycle in EEPROM v Verbose output v v for more q Quell progress output q q for less Display this usage avrdude project lt URL http savannah nongnu org projects avrdude gt Solution 2 12 avrdude AVR device initialized and ready to accept instructions Reading fHHHHHHHHHHEHHHHHHBHHHHHHBHHHHHHHHHHHHHBHHHHHHHHNHE 100 0 02s avrdude Device signature 0x1e9702 avrdude safemode Fuses OK avrdude done Thank you Solution 2 13 avrdude AVR device initialized and ready to accept instructions Reading fHHHHHHHHHBEHHHHHHHHHHHHHBHHHHHHHHHHHHHBHHHHHHHHNHE 100 0 02s avrdude Device signature 0x1e9702 avrdude reading input file bt cmd btnode3 hex avrdude writing flash 66182 bytes 94 APPENDIX B SOLUTIONS Writing fHHHHHHHHHHEHHHHBHHHHHHHHHHHHHHHHHHHHHHHBHHHHHHHHRHE 100 14 47s
165. printf nEnter the message user input stdout message 161 send sms send sms pdu mode number message disconnect bt_rfcomm_disconnect 2 main function that initializes the hardware led terminal bluetooth and acl communication stack and registers some predefined commands Use tab tab to see the registered commands once the program is running int main void serial baud rate u_long baud 57600 hardware init btn_hardware_init btn_led_init 1 init app uart NutRegisterDevice amp APP_UART O 0 freopen APP_UART dev_name r stdout _ioctl _fileno stdout UART SETSPEED amp baud hello world printf_P PSTR n printf_P PSTR n Welcome to BTnut 2005 ETH Zurich n printf_P PSTR rfcomm cmd program version s n PROGRAM VERSION printf_P PSTR printf_P PSTR nbooting bluetooth module bluetooth module on takes a while btn hardware bt _ Start the stack and let the initialization begin Stack bt hci init amp BT UART bt hci write local cod stack BT HCI SYNC 200 printf P PSTR ok NnNr give hint printf P PSTR hit tab twice for a list of commands n r terminal init btn terminal init stdout rfcomm cmd bt_cmds_init stack Start L2CAP and RFCOMM 12cap_stack bt l2cap init stack 8 8 BT_L
166. put a return 0 or similar statement at the end of main even though main is defined as having an int return value This allows the compiler to throw an error during compilation in case the last line of your program should ever be reached it shouldn t really Obviously an empty program is not very exciting Let s see how the LED control described in the previous chapter can be implemented through BTnut OS function calls Explanation Using the on board LEDs BTnut OS offers through lt led btn led h gt the functions void btn_led_set u_char nr and void btn_led_clear u_char nr where nr denotes the LED in question namely 0 through 3 Before the LEDs can be controlled this way we need to initialize them first include lt hardware btn hardware h gt for btn_hardware_init include lt led btn led h gt for led related functions int main void 1 btn hardware init initialize SRAM btn_led_init 0 initialize LEDs btn_led_clear 0 btn_led_set 1 btn_led_clear 2 btn_led_set 3 for endless loop main should never return where to Notice the argument that btn_led_init takes it indicates whether we want to activate an LED heartbeat i e the periodic blinking of one or more LEDs to indicate that our BTnode is alive as we didn t want a heartbeat in the above example we used 0 For more information on LED heartbeats see page Exercise 4 1 Write a p
167. r number_str char number char buffer 3 NO int length init number_str 0 0 if number skip character in phone number number length strlen number if length gt 15 invalid phone number return number_str else itoa length buffer 16 convert integer to hex string strcat number str buffer strcat number str 91 120 APPENDIX B SOLUTIONS while number NO amp amp number 1 0 buffer 0 number 1 buffer 1 number buffer 2 0 strcat number_str buffer number 2 if length 4 2 OX buffer 0 f buffer 1 number buffer 2 0 strcat number_str buffer return number str void send sms pdu mode char number char message char pdu 172 0 char buffer 13 0 int length char rdbuffer 4 0 char number_str 19 0 char message str 147 NO message header strcat pdu 0025000 process phone number if process phone number number str number 0 0 invalid phone number return strcat pdu number str process message process message message str message strcat pdu message str pdu length length strlen pdu 2 1 line delimiter strcat pdu 1 at commands strcpy buffer at cmgs itoa length rdbuffer 10 strcat buffer rdbuffer strcat buffer r sm
168. ram that continously reads out and prints the value from the BTsense logic level motion sensor If you do not know to which port it is connected see ex above 10 2 3 Analog Sensors Analog sensors do not simply deliver an off on value but output a different voltage level for each possible sensor reading In order to use this information in a program this voltage level needs to be sampled into a binary value typically between 0 255 i e 8 bit resolution though up to 10 bits resolution are supported on the ATmegal28L 80 CHAPTER 10 BTNODES AND SENSORS Digitizing analog data on the ATmegal28L is generally simple its built in Analog Digital Converter ADC supports up to 8 different analog input channels two of which optionally amplify the signal 10 or even 200 times noise cancellation and either single or continuous conversion modes One only needs to properly setup the various needed parameters trigger a conversion and subsequently read out the resulting digital values Each of these steps can be controlled through one or more ATmegal28L registers Explanation Using the ATmega128L ADC ADC setup is performed through the ADC Control and Status Register ADCSRA where for example the ADC can be enabled and disabled bit 7 ADEN and single conversions can be triggered bit 6 ADSC The ADC Multiplexer Selection Register ADMUX allows the selection of input pins as well as voltage reference and input gain setu
169. rdude pm128 cavrispv2 P dev ttySO s U flash w uart echo btnode3 hex i WARNING DO NOT USE OTHER LOW LEVEL COMMANDS WHEN IN SYSTEM PRO GRAMMING UNLESS YOU KNOW WHAT YOU ARE DOING AS IT COULD DAMAGE THE MICROCONTROLLER Exercise 2 16 Now go back to the bt cmd application in Eclipse that we modified earlier and save the changes we have made Open a command line shell om this directory Compile the bt cmd application by entering make btnode3 Then upload the newly compiled application to the BTnode with make btnode3 upload Observe the different LED heartbeat compared to the pre compiled bt cmd btnode3 hex we uploaded earlier Check the terminal program for output Hit Tab twice to get a selection of commands possible in the bt cmd application Explore the different functions available in this demo application Try to locate different BTnodes by issuing bt inquiry sync 16 CHAPTER 2 FIRST STEPS IN BTNODE PROGRAMMING Explanation The bt cmd demo application The bt cmd demo application is a brief example of how to use the Bluetooth radio and protocol stack Once the application has booted and is ready on a serial terminal with 57 6k 8N1 no handshake you can check the list of available commands by hitting Tab twice Welcome to BTnut c 2006 ETH Zurich bt cmd program version 20060405 1206 Id firststeps tex v 1 15 2007 01 22 16 40 02 beutel Exp running 0 7 3628 MHz NutFreq 10241 Hz booting Bluetooth module
170. rogram that endlessly rotates through the four LEDs i e it turns one after another on and off Observe the output Use for statements to slow the rotation down until it becomes easily visible 4 3 THE TERMINAL 29 Optional Exercise 4 2 Have your program from Ex terminate after a few rotations you will need to add return O to the end to get it to compile What behavior do you observe 4 3 The Terminal In order to communicate back to the user or programmer we are not restricted to using the on board LEDs only Through our USB cable we can setup our BTnode in such a way that printf statements provide output that can be printed in a terminal program on our PC and use fscanf to read user input from within the terminal program and input it back into our BTnut program This is where the ATmega128 UART ports Universal Asynchronous Receiver Transmitter come into play Actually the ATmega128 supports USART ports Universal Synchronous Asynchronous Receiver Transmitter Consequently you will notice that some libaries and functions actually use usart in their names However as it does not make much of a difference and as UART is the much more common interface we will continue to use that term The ATmegal28 has two UART interfaces UARTO and UART1 While UARTO is used to connect the ATmega128 to the Bluetooth module we can use UART1 to write ASCII text to the terminal i e a program running on the host computer that uses well
171. rresponds to the ADC value 1024 Therefore 0 5V corresponds to an ADC value of 1024 3 3 0 5 155 A battery voltage is 2V ADC value is 310 define BAT_1_VOLT 155 define BAT_2_VOLT 310 int adc_done 0 int battery_voltage 0 u_char temp_sreg void shortpause u_short duration u_short i for i 0 i lt duration i 1 void pause u_short duration u_short i for i 0 i lt duration i shortpause Oxffff void write_led u_char value volatile u_char pointer u_char dummy pointer u_char u_short value lt lt 8 dummy pointer sbi PORTB 5 asm volatile nop cbi PORTB 5 int get_battery_volt void int result ADMUX 1 MUXO ADMUX 1 MUX1 ADCSRA 1 ADPSO ADCSRA 1 lt lt ADPS1 ADCSRA 1 lt lt ADPS2 ADCSRA 1 lt lt ADEN ADCSRA 1 lt lt ADSC while ADCSRA amp 1 lt lt ADSC result ADCL result ADCH lt lt 8 return result 103 static void timer3IRQ void arg int battery voltage get battery volt if battery voltage lt BAT 1 VOLT write led 0x02 else if battery_voltage lt BAT_2_VOLT write_led 0x04 else write_led 0x08 Reset the counter to non zero value see expl in main routine TCNT3H 0x21 TCNT3L 0x64 adc_done 1 init_stdout void u_long baud 57600 sbi PORTD 2 NutRegisterDevice amp APP_UART
172. rs are a less resource intensive way of manually polling e g in a loop a sensor value They are well suited for periodic measurement tasks e g for documenting the temperature every 10 minutes over the course of a day Sometimes however it is necessary to quickly react to a change in the measured data Instead of increasing the polling frequency and thus tying up CPU cycles we can use an interrupt to get automatically notified of changing values The ATmegal28L offers eight external interrupt request lines i e pins that can automatically trigger the execution of a particular code snippet and several internal interrupts i e for monitoring internal processes such as the above mentioned counter overflows Table 10 2 lists selected signals in BTnut for a complete list of interrupts see section Interrupt Vectors in the ATmegal28L manual I When interrupts are enabled the processor will automatically interrupt the normal program flow and execute a previously registered interrupt service routine ISR As ATmegal28L interrupts always have a higher priority than regular program code 82 CHAPTER 10 BTNODES AND SENSORS Mode Description NUT IRQMODE LOWLEVEL Signal as long as level is low NUT IRQMODE FALLINGEDGE Signal when level changes to low NUT IRQMODE RISINGEDGE Signal when level changes to high NUT IRQMODE EDGE Signal whenever level changes Table 10 1 BTnut external interrupt modes the
173. rystal u_long nut_tick_freq hardware init btn_hardware_init btn_led_init 1 init app uart NutRegisterDevice amp APP_UART 0 0 freopen APP_UART dev_name r stdout _ioctl _fileno stdout UART_SETSPEED amp baud logging log_init hello world printf n Ys printf n Welcome to BTnut c 2006 ETH Zurich n printf bt cmd program version s n PROGRAM VERSION printf s n CVS VERSION cpu crystal NutGetCpuClock nut tick freq NutGetTickClock printf running u 04u MHz NutFreg ul Hz n int cpu_crystal 1000000UL int cpu_crystal cpu_crystal 1000000UL 1000000UL 100 int nut_tick_freg printf 4 n printf nbooting Bluetooth module n bluetooth module on takes a while btn hardware bt onO verbose debug of all hci information bt hci debug uart 1 Start the stack and let the initialization begin Stack bt hci init amp BT UART bt hci write default link policy settings stack BT HCI SYNC BT HCI LINK POLICY ROLE SWITCH 117 BT HCI LINK POLICY HOLD MODE BT HCI LINK POLICY SNIFF MODE BT HCI LINK POLICY PARK STATE bt addr t addr struct bt hci local version result version u char features 8 u_char bt cmds name 30 bt hci read bt addr stack BT HCI SYNC addr prin
174. s format pdu bt rfcomm send 2 at cmgf 0 r 10 NutSleep 1000 sms command bt rfcomm send 2 buffer strlen buffer NutSleep 1000 message bt rfcomm send 2 pdu strlen pdu insert some delay to receive the send ok message NutSleep 5000 void send sms char arg bt addr t BTaddr 0x6d 0x30 Oxci Ox9f 0x11 0x00 unsigned int addr BD ADDR LEN int i char BTaddress 18 NO char number 17 NO char message 161 Greetings from the BTnode interface for Bluetooth address input printf nEnter the Bluetooth address or the name of the sending phone user input stdout BTaddress 18 extracting the BTaddress if sscanf BTaddress 2x 2x 2x 2x 2x 2x amp addr 5 amp addr 4 amp addr 3 amp addr 2 amp addr 1 amp 0 6 for i 0 i BD ADDR LEN i BTaddr i u_char addr i y 121 connect if bt rfcomm start session BTaddr O 0 return NutSleep 1000 if bt rfcomm connect 1 con cb rcv cb line cb credit cb 10 NULL return NutSleep 1000 general AT Commands bt rfcomm send 2 at amp f r 5 NutSleep 2000 bt rfcomm send 2 at cgmi r 8 NutSleep 1000 bt rfcomm send 2 at cgmm r 8 NutSleep 1000 bt rfcomm send 2 at cgsn Wr 8 NutSleep 1000 user interface for SMS messaging printf nEnter the phone number of the recipient user input stdout number 17
175. s located on the Bluetooth radio and comprises the HCI firmware the link manager firmware and the baseband controller HCI commands can be sent from the host to the controller to initiate radio communication and access configuration parameters On the other hand the controller uses HCT events to inform the host when something occurs Finally HCT data packets may be transmitted in both directions Bluetooth Host BTnut ACE UART m NUT OS I HCI Events Host Controller Interface HCI Data Packets HCI Commands AY Link Manager Firmware AY AY Baseband Controller Bluetooth Controller Exercise 7 1 Each Bluetooth device is characterized by a unique Bluetooth device address Find the device address MAC of your BTnode How many bytes are needed to represent a Bluetooth device address A HCI packet is defined as shown below struct bt_hci_pkt_cmd u_char type u_char payload 255 3 The type parameter is needed to distinguish between command event and data packets For our purpose we set type 0x01 to define a command packet The payload array reserves 255 bytes for the actual command packet as specified on page 509f of the Bluetooth specification 6 It starts with a 2 byte OpCode which is divided into two fields called Opcode Group Field OGF and OpCode Command Field OCF Note that the bit ordering of the packet definition follows the Little Endian format i e the LSB is the first bit s
176. s superb introduction modification Apr 19 2006 2 jb Replaced 115200 by 57600 default baudrate May 29 2006 6 jb cm Bluetooth updates for 2006 created version 1 3 Nov 13 2006 7 my Added chapter 7 Jan 08 2007 9 10 jb Added chapters 9 amp 10 by Marc Langheinrich Jan 15 2007 all jb Added tutorial overview and changed solution numbering Jan 17 2007 all my complete review with minor changes Jan 22 2007 Version 1 5 Table 1 Revision History Chapter 1 Introduction 1 1 The BTnodes and the BTnut System Software Figure 1 1 The BTnode rev3 The BTnode is an autonomous wireless communication and computing platform based on a Bluetooth radio and a microcontroller 8 It serves as a demonstration platform for research in mobile and ad hoc connected networks MANETS and distributed sensor networks The BTnode has been jointly developed at ETH Zurich by the Computer Engineering and Networks Laboratory TIK and the Research Group for Distributed Systems Currently the B Tnode is primarily used in the NCCR MICS research projects In addition to its Bluetooth radio the latest BTnode revision rev3 2 also features a low power radio identical to the one used on the Crossbow Berkeley Mica2 Motes 8 allowing it to interact with both Mica2 based nodes and previous Bluetooth only revisions of the B Inode Both radios can be operated simultaneously or be independently powered off completely when not in use
177. se a terminal to initiate a certain LED pattern which will be set on each receiving node before sending the packet on to other nodes 9 3 2 Frequency Control The CC1000 radio supports a wide variety of frequencies primarily in the ISM bandg at 315 433 868 and 915 MHz However it can be also tuned to almost any frequency between 300 and 1000 Mhz 4 During B MAC initialization the radio is set to 868 5 MHz However if desired one can use the cc1000 set function in cc1000 h to set it to one of 65 predefined frequencies in the 915 and 868 MHz bands as defined in cc1000 defs h include lt cc bmac h gt include lt cc ccc h gt include lt cc cc1000_defs h gt include lt cc cc1000 h gt define address node cluster cluster lt lt 5 node define NODE ADDRESS address 27 34 node 27 cluster 34 static void init_radio void bmac_init NODE ADDRESS inits radio to 868 5 MHz cc1000 set FREQ 915 430 MHZ reset radio frequency broken in release 1 6 ccc init amp Kbmac interface Unfortunately the cc1000 set function is broken in the BTnut 1 8 system release This will hopefully be fixed soon The cc1000 tune manual function offers even more control over the CC1000 frequency The function takes the desired frequency in Hz to avoid fractional values and returns the actual frequency that has been set as not all frequencies can be achieved on the CC1000 uint3
178. st be taken with such multicast addresses i e addresses that are multiple of 32 minus one 31 63 95 as data sent to such an address will be received by all other nodes in this particular cluster When accidentially assigning such an address to a node e g using bmac init 63 all packets sent to it will also be delivered by the B MAC layer to all other nodes in this particular cluster e g 32 through 62 in this case Also note that cluster 2047 does not have an individual multicast address as OxFFFF is actually used as a broadcast address for all nodes In order not to accidentially assign multicast addresses to nodes use the following macro to compose an address from separate node and cluster IDs define address node cluster cluster lt lt 5 node When using ccc send we will need to take care of properly packaging our data In case of binary data this means making sure that multi byte data e g 16 bit shorts are put in a well defined order otherwise the receiver might accidentially reverse those bytes during decoding This is because not all microprocessors 70 CHAPTER 9 THE CHIPCON RADIO Address Node ID Cluster ID 0x0000 0 0 OxOO1E 30 0 OxOO1F ALL 0 0x0020 0 1 0x002E 30 1 0 002 ALL 1 OxFFCO 0 2046 OxFFDE 30 2046 OxFFDF ALL 2046 OxFFEO 0 2047 OxFFFE 30 2047 OxFFFF ALL ALL Table 9 1 Cluster Addresses The B MAC layer divides the 16 bit address space in
179. stration function calls Insert the callback function definitions and the other lines printed below define MIN CREDITS 10 define MAX CREDITS 40 void rcv cb u char dlci u_char payload u short len void arg 1 u short idx if len gt 0 printf n for idx 0 idx lt len idx printf c payload idx void con_cb u_char dlci u_char type void arg if type BT_RFCOMM_CONNECT printf RFCOMM Connect on dlci d n dlci bt_rfcomm_send_credits dlci MAX_CREDITS BT_RFCOMM_DEF_CREDITS else printf RFCOMM Disconnect on dlci d n dlci void line_cb u_char dlci u_char flags void arg printf rfcomm Line status has changed dlci 4d flags 02x n dlci flags void credit_cb u_char dlci u_char credits void arg printf rfcomm Credits running low for dlci d Credits remaining d n dlci credits printf rfcomm Send new credits MAX CREDITS credits bt rfcomm send credits dlci MAX CREDITS credits Write a function that opens a RFCOMM connection to a cell phone on RFCOMM channel 1 using the bt_rfcomm_start_session and bt_rfcomm_connect functions Include some delay after each function call e g NutSleep 1000 HINT For the callback arguments pass the names of the copied functions Afterwards send some general AT Commands see below and close the RFCOMM connections using the function bt_rfcomm_send in the former and the function bt_r
180. t NutThreadCreate my_thread my_thread 0 192 for 1 printf main is alive n NutSleep 1000 return 0 Solution 5 7 include lt stdio h gt include lt dev usartavr h gt include lt sys thread h gt include lt sys timer h gt include lt sys tracer h gt include lt hardware btn hardware h gt include lt sys osdebug h gt include lt terminal btn terminal h gt int init_stdout void u_long baud 57600 sbi PORTD 2 NutRegisterDevice amp APP_UART O 0 freopen APP_UART dev_name r stdout _ioctl _fileno stdout UART SETSPEED amp baud return 1 THREAD my thread arg 106 APPENDIX B SOLUTIONS for f printf s is alive n runningThread gt td_name NutSleep 1000 void create char arg char 20 int val strange behavior here typing create name does not work but create name does val sscanf arg s name if val 1 printf Create a thread with name s n name if 0 NutThreadCreate name my_thread 0 292 printf FAILED n else printf SUCCESFUL n int main void hardware init btn_hardware_init init_stdout btn_terminal_init stdout bt cmd btnode btn_terminal_register_cmd create create btn_terminal_run BTN_TERMINAL_NOFORK 0 return 0 Solution 5 8 include lt stdio h gt include lt dev usartavr h gt include lt sys thread h gt inc
181. t and ntohs network to host short to convert between this network byte order where the most significant byte is put first and the host byte order i e whatever the current host s and or used compiler s order is void cmd send ushort char arg int val pkt gt length 2 if sscanf arg 4u amp val 1 put two byte value in network order into packet u short amp pkt gt data 0 htons u short val alternatively do this manually pkt gt data 0 val gt gt 8 high byte pkt gt data 1 val amp OxFF low byte if ccc send BROADCAST ADDR PACKET TYPE pkt 1 send failed lt gt 0 indicates error 5Notice that the concept of endianness is less important with regards to the individual bits as access to bits is usually not given directly but through well defined logical operators that work independant of the actual representation 9 2 ACCESSING THE CC1000 71 The second argument to ccc send is a packet types Packet types allow us to simplify packet receiption as each different type can trigger a different reception function so called packet handlers l his is explained in the following section 9 2 3 Receiving Data The ccc rec Receiver Thread As we have seen in exercise above calling ccc init automatically activates a ccc rec thread that will repeatedly listen for incoming packets on the CC1000 radio The ccc rec thread is started with th
182. t written or none If an interrupt occurs in the middle of such an assignment the already written first byte might not be the same anymore by the time program control returns to the main program BTnut offers the NutEnterCritical and NutExitCritical functions in sys atom h to allow main program code to run uninterrupted As with ISR code these parts of code should be as short as possible in order not to loose any interrupt signals Note that NutExitCritical does not simply re enable interrupts Instead 10 3 READING SENSOR DATA 83 Signal Description sig ADC ADC conversion complete sig COMPARATOR Analog comparator sig INTERRUPTO External interrupt 0 sig INTERRUPTI External interrupt 1 sig INTERRUPT2 External interrupt 2 sig INTERRUPT3 External interrupt 3 sig INTERRUPTA External interrupt 4 sig INTERRUPT5 External interrupt 5 sig INTERRUPT6 External interrupt 6 sig INTERRUPT External interrupt 7 sig SPI SPI interrupt entry sig INPUT CAPTUREI Timer 1 input capture sig INPUT CAPTURE3 Timer 3 input capture sig OUTPUT COMPAREO Timer 0 output compare sig OUTPUT COMPARELA Timer 1A output compare sig OUTPUT COMPAREIB Timer 1B output compare sig OUTPUT COMPAREIC Timer output compare sig OUTPUT COMPARE2 Timer 2 output compare sig OUTPUT COMPARE3A Timer 3A output compare sig OUTPUT Timer output compare sig OUTPUT COMPARE3C Timer output com
183. tPostAsync and NutEventBroadcastAsync respectively in order to continue being in the RUN NING state Both routines perform exactly the same signaling as their regular counterparts yet without executing a context switch This can be done later using e g a NutThreadYield or NutSleep Exercise 5 17 In order to gain understanding of threads and thread coordination we will now write a ping pong game We have two players standing at opposing ends of a table that hit a ball back and forth and every time a player misses the table the other player scores The player that first reaches 11 points wins In order to implement this we will need two players 0 and 1 one ball and one coordinator referee that keeps track of points The sequence of events will look as follows 1 The current player will play the ball initially player 0 2 The ball will move across the table and either hit or miss the table 3 In case the ball misses the table the referee scores one point for the opponent If this player has reached 11 points the referee ends the game and declares this player winner 4 The sequence repeats at point 1 with player 0 and 1 alternating turns If the last ball missed the table the next player will serve otherwise the point just continues until one player misses the table Implement this algorithm on the BTnode All the actors in the game will be implemented as a separate thread coordination among threads is achieved
184. tf Bluetooth MAC address 2x 2x 2x 2x 2x 2x n addr 5 addr 4 addr 3 addr 2 addr 1 addr 0 bt hci read local version information stack BT HCI SYNC amp version printf HCI version AX 4X 4X 4X 4X n version hciversion version hcirevision version lmpversion version manufacturername version lmpsubversion bt hci read local supported features stack BT HCI SYNC features printf LMP features 2X 2X 2X 2X 2X 2X 2X 2X n features 0 features 1 features 2 features 3 features 4 features 5 features 6 features 7 bt hci read local name stack BT HCI SYNC bt cmds name sizeof bt cmds name printf Local name s n bt cmds name give hint printf hit tab twice for a list of commands Wn Wr terminal init char prompt 20 sprintf prompt bt cmd 2x 2x addr 1 addr 0 btn terminal init stdout prompt bt cmds init stack bt cmds register cmds btn cmds register cmdsO nut cmds register cmds log_cmds_init stdout bt_hci_register_acl_cb stack receive struct bt_hci_pkt_acl acl_pkt NULL btn terminal register cmd transmit transmit terminal mode btn terminal run BTN TERMINAL NOFORK 0 return 0 Solution 8 6 so inc inc inc inc inc inc inc inc inc inc inc inc inc inc inc inc inc inc inc inc inc inc def FILE stru stru stru ution to all pr
185. the counter to non zero value see expl in main routine TCNT3H 0x21 TCNT3L 0x64 main void int toggle 0 DDRB 1 lt lt DDB5 NutRegisterIrqHandler amp sig_OVERFLOW3 timer3IRQ 0 16 bit timer without prescaler clock frequency 7 3MHz gt overflows once every Oxffff 1 7 3E6 s 9ms For an overflow every 2s prescaler should be 2s 9ms 223 The closest value is 256 see table on page 135 This gives an overflow every 2 3s This could be adjusted by setting the counter value to 0 3 2 3 0xfffff 0x2164 after every overflow thus at the end of the timer interrupt routine TCCR3B 1 lt lt CS32 ETIMSK 1 lt lt TOIE3 while 1 if toggle toggle 0 write_led 0x01 else toggle 1 write_led 0x00 pause 10 return 0 Solution 3 6 include lt hardware btn hardware h gt include lt dev irqreg h gt COMPUTE ADC values corresponding to 1 and 2 Volts If battery voltage is 1V the BAT_SENSE signal is 0 5V The reference voltage is 3 3V and corresponds to the ADC value 1024 Therefore 0 5V corresponds to an ADC value of 1024 3 3 0 5 155 A battery voltage is 2V ADC value is 310 define BAT 1 VOLT 155 define BAT 2 VOLT 310 void shortpause u short duration i 99 u short i for i 0 i lt duration i 1 void pause u short duration i u short i for i 0 i lt duration i 1 shortpause Oxffff
186. the new file 3 Step through the code until the yellow arrow is on the printf statement Expand the processor item in the I O workspace Remember the cycle count 4 Proceed one step step over Compare the cycle counter with the previous values How many cycles did it take 5 Normally printf statements have formatted output Replace the existing printf statement with printf UART baudrate u u kbaud n int baud 1000UL int baud baud 1000UL 1000UL 100 6 Compare the cycle count of the formatted printf with the unformatted one 6 5 The OS Tracer Printf is often used for debugging However in the previous section we have seen that this method has a relatively large overhead Thus it is not suitable for tracing frequent events such as interrupts or thread switches For such events the tracer tool is more appropriate 6 5 THE OS TRACER 45 Explanation Tracer Tool Interactive Mode The tracer tool stores information about important OS events in memory and prints this information later on the terminal for analysis purposes Important OS events include thread switches due to sleeps yields priority changes etc and interrupts In addition to the type of event the exact system time microsecond resolution and additional information e g which thread did a sleep is stored The tracer tool can be used in various different ways The most simple is the interactive terminal mode To activate the tool
187. then how we can use BTnut to use this information in our program 10 1 ATmegal28L I O Ports and Registers The ATmegal28L microprocessor features 53 programmable I O lines It is through these lines that all communication to and from the processor takes place While all 53 lines can be used in a totally generic fashion i e they can both be used to output a bit as well as reading input bits all of them also have at least one so called alternate function i e they are connected to a specific on chip feature such as the analog digital converter the UART a hardware timer or an external interrupt signal It is up to the programmer either from within the OS or as part of the application to properly choose how a particular I O line should be used as a generic output line as part of an ADC conversion to monitor an input line and throw an interrupt whenever it changes to control a set of digital sensors via a sensor bus such as the I C interface etc Figure 10 2 shows all 64 pins of the ATmegal28L PA though PG are the seven available I O ports with ports A through F having 8 pins each while port G has only five pins Each port is represented through three registers each which together provide for each pin of each port access to its I O functionality the Data Direcion Register DDRx where stands for A through defines whether a particular pin on a port will be used for input or output while the Data Register PORT
188. to an OCxn pin Optional Exercise 10 9 Describe the steps necessary to put the same 440Hz signal onto an arbitrary I O pin of the ATmega128L e g pin What is the difference to the solution in ex 10 8 TCNTn OCn Toggle 1 0 1 Figure 10 3 Waveform generation in CTC mode I Notice the variable signal periods due to varying TOP values horizontal bars 86 CHAPTER 10 BTNODES AND SENSORS 10 4 The btsense library Many of the low level details for querying sensor data off the B Isense sensor board have already been encapsulated in dedicated functions as part of the btsense library While it might still be necessary to use BTnut timers interrupts or hardware timers to read out sensor values periodically and or automatically these functions should greatly simplify the act of reading out each of the three sensors as well as driving the connected buzzer Explanation Using the library for BTsense The btsense library offers three functions for reading out each of the three sensors as well as a function for driving the buzzer with a particular frequency It takes care to properly set all required hardware registers as well as configure both the ADC and any necessary timer counters Note that the btsense init function requires a board revision identifier typically this should be BTSENSE REVSION 1 1 include lt btsense btsense h gt int main void btnode_init init hardware uart network
189. to clusters with 31 nodes each One address per cluster is reserved for so called cluster multicast while the highest address OxFFFF broadcasts to all nodes in all clusters nor compilers for that matter represent multi byte values in the same order Intel chips have traditionally arranged multi byte values in memory by beginning with the least significant byte LSB first i e the value 0x1234 stored at say memory address 0x3201 would have the value 34 at 0x3201 and value 12 at 0x3202 This is called little endian order Consequently beginning with the most significant byte MSB first would store value 12 at 0x3201 and value 34 at 0x3202 This is called big endian order This endianness becomes crucial when exchanging multi byte data e g integers between platforms e g through binary files an image or over the network Explanation Network Byte Order As long as the data we send is picked up by identical hardware running identical software built using the same compiler we can ignore byte order as both sender and receiver will use the same representation However for exchanging data between different platforms or between software from different generations vendors or compilers agreeing on a common byte order is crucial For network exchanges e g over Ethernet but also wirelessly the commonly agreed upon network byte order uses big endianness There are standard C functions htons host to network shor
190. tput waveform for the microcontroller pins used that switch the LEDs on and off What are the problems arising from this hardware setup for a software system especially in the case of an operating system with concurrency multiple drivers tasks threads How would you implement a software driver for this functionality Why is SBI CBI set bit and clear bit not sufficient in this case 2 4 BTNUT SYSTEM SOFTWARE RESOURCES 9 c 01 2005 22533 o lt lt c E a et 8 e a v ey dm 9n gt pp RrI o0U0UUu uu ST T Bi Cs 7 een t P4399 75 sr sa T
191. urn and the thread with the highest priority among those that are ready to run is given the CPU If no ready to run thread has a higher priority than the current thread NutThreadYield returns immediately Explanation Giving up Control In order to support concurrent threads on the BTnode each thread even the mainO function must periodically yield control A call to Nut ThreadYield basically means Is there any process that is more important than myself If so feel free to take over control Otherwise I will simply continue Once control has been given away and is returned at a later point in time the thread will continue to run right after the call of NutThreadYield If a thread has nothing to do it can also force cease of control by calling NutSleep time This function puts the current thread into SLEEPING mode and transfers control to any thread that is waiting for control i e is READY see below If no thread is waiting the idle thread takes over which is always ready to run but which has the lowest priority see below Note that threads might also give up control involuntarily in case of an interrupt See the BTnut documentation for details Explanation BTnut System Threads We have already encountered a number of threads before created and run by the BTnut OS the LED thread see page and excercise 4 3 the terminal thread see section 4 3 and excerise 4 4 as well as the idle thread and the main threa
192. use include lt sys tracer h gt btn terminal register cmd trace NutTraceTerminal as it has been explained in the previous section Preparation The current version of the btnut binaries does not flag OS events for the tracer Therefore the sources have to be recompiled with the DNUTTRACER option 1 Open the file Makedefs located in the folder btnut 2 Uncomment the line DEFS BTNODE3 DNUTTRACER 3 Recompile the sources make clean install in folder btnut Exercise 6 6 This exercise is a step by step tutorial for using the trace tool First write a program that starts the LED thread then registers the trace terminal command and then starts the terminal thread Run this program and continue as follows 1 Type trace you will get the output es ex3 trace TRACE STATUS Mode is OFF Size is O contains 0 elements SYNTAX trace print size loneshot circular size lt size gt stoplmask lt tag gt 2 Type trace oneshot and then type trace again If you have not waited too long between the two commands you will get something like this es ex3 trace oneshot TRACE mode ONESHOT restarted es ex3 trace TRACE STATUS Mode is ONESHOT Size is 500 contains 77 elements SYNTAX trace print lt size gt oneshot circular size lt size gt stop mask lt tag gt Typing trace again will give you a similar status except that the contains XX elements shows an increasing number When it has reached 50
193. ve This thread shall repeatedly turn on the blue LED using btn Led set LED0 and switch off the red LED using btn led clear LED1 HINT LEDO and LED1 are just macros for the numbers we were using before i e 0 and 1 respectively However using symbolic names instead of numbers makes our programs more portable The main routine after having created the thread shall do the opposite i e turn on the red LED and switch off the blue LED Which LEDs are switched on Why Add a single NutThreadYield such that the other LED is switched on Add a second NutThreadYield such that both LEDs are switched on by turns you will see both LEDs switched on because the main routine and the thread alternate very quickly 5 3 THREAD CONTROL 35 5 3 Thread Control Exercise D 1 has demonstrated the cooperative nature of the BTnut OS In order to have two or more threads running they need to repeatedly and continously give up control of the CPU and other resources so that other threads may run In principle we will see an exception later on active i e running threads only yield the CPU to other threads if this is explicitly coded The most simple way to do this is NutThreadYield a function that has no parameters This function causes the OS to check whether other threads with higher priority are ready to run we will explain thread priorities below If this is the case the current thread is suspended i e NutThreadYield does not ret
194. ware btn hardware h gt include lt led btn led h gt HANDLE event int init_stdout void u_long baud 57600 sbi PORTD 2 NutRegisterDevice amp APP_UART O 0 freopen APP_UART dev_name r stdout _ioctl _fileno stdout UART_SETSPEED amp baud return 1 THREAD my_thread arg int count 0 for NutEventWait amp event NUT WAIT INFINITE count printf myThread has received event no d n count int main void 1 init_stdout NutEventPost kevent printf main posts an event n NutEventPost amp event printf main posts an event n NutThreadCreate myThread my_thread 0 192 printf main enters endless loop n for 33 NutThreadYield return 0 Solution 5 13 include lt stdio h gt include lt dev usartavr h gt include lt sys thread h gt include lt sys timer h gt include lt sys tracer h gt include lt sys event h gt include lt hardware btn hardware h gt include lt led btn led h gt include lt string h gt HANDLE event void shortpause u_short duration u_short i for i 0 i lt duration i Y 109 void pause u short duration 1 u short i for i 0 i lt duration i 1 shortpause Oxffff int init_stdout void u_long baud 57600 sbi PORTD 2 NutRegisterDevice amp APP_UART 0 0 freopen APP_UART dev_name r stdout _ioctl _fileno stdout UART_SETSPEED amp baud r
195. within a register For example PB5 is an alias for 5 since the PB5 bit is the fifth bit within the PORTB register counted from the left starting with 0 Examples if PORTB amp 1 lt lt PB5 checks whether the PB5 bit is set PORTB 1 lt lt PB5 sets the PB5 bit to one PORTB amp 1 lt lt PB5 clears the PB5 bit Exercise 3 1 To check whether you have understood how LEDs are controlled use the BTnode schematics to figure out the value needed to switch on the blue LED Explain the computation of pointer As a start we write a program that blinks with the blue LED The main routine thus looks as follows include lt hardware btn hardware h gt int main void DDRB 1 lt lt DDB5 while 1 toggle the blue LED wait a second return 0 Explanation Configuring the direction of IO ports The line before the infinite loop configures the fifth bit of the DDRB register DDRB stands for Data Direction Register of Port B and this operation declares the fifth pin of port B to operate as an output pin After this line you are free to use the write led function shown above See pages 63ff in the ATmegal28 manual for a detailed explanation 3 8 ON CHIP RESOURCE THE ANALOG TO DIGITAL CONVERTER 21 Exercise 3 2 Complete now the program sketched above In order to see what your program does you will have to implement a pause function Do this using a loop that increments a counter variabl
196. x and Port Input Pin PINx register among other features provide access to output and input values of each pin respectively Page 84 of the ATmegal28L manual 1 gives an overview of all I O port registers Additionally more than one hundered registers can be used to enable or disable a certain alternate function of each pin For example the ADCSRA register controls the analog digital converting unit like turning it on and off and starting a conversion while the ADMUX register controls which of the potential input pins pins 0 through 7 of port F are to be used during the conversion Each of these registers see the ATmegal28L manual 1 on page 364 for a complete list is provided to the programmer as a so called hardware register While programmers typically understand the term register to be a processor register a small amount of very fast on chip memory that is used to hold intermediate values during a computation in a very efficient manner hardware registers are much more common in embedded systems programming They often look and feel like being just another memory value yet they physically control access to various devices The avr libc defines mnemonicq identical to the ones used in the ATmegal28L manual as shorthands in order to allow statements of the form enable ADEN in the ADCSRA register instead of set bit 7 of register 0x0026 to 1 lActually these are precompiler definitions which can be found in
197. y be changed using ioctl see the avr gcc manual for details then a string that is longer Enable the tracing of interrupts Explain what you see 49 Chapter 7 Communication Using Bluetooth 7 1 Introduction The Bluetooth technology is well suited to provide short range wireless communications between electronic devices like e g mobile phones laptops or PDAs Without the need of a pre established infrastructure portable devices may create links and form Personal Area Networks PANs This chapter addresses simple point to point communication between BTnodes We will mainly concentrate on the interaction between the microcontroller and the Bluetooth radio and will as far as possible make use of pre implemented data structures and functions of the BTNut system software In doing so the reader should gain some insight in the use of the thread event functionality of the Nut OS and the low level packet assembly routines provided by the BTnut API To gain a certain confidence and understanding of Bluetooth communication you can use the bt cmd demo application We will have to familiarize the reader with certain details of the Bluetooth Specification 6 In order to ease searching in the specification all page numbers given in this tutorial refer to the page numbers of the PDF document Section 7 2 presents the basic mechanisms that are used to access the Bluetooth radio capabilities Therefore the interface between microcontr
198. y will be executed almost immediately when their interrupt condition holds true allowing for almost real time handling of events Explanation Using interrupts in BTnut In order to activate a particular interrupt in BTnut we simply need to register an interrupt handler a so called interrupt service routine with the corresponding interrupt signal The NutRegisterIrqHandler function takes a signal an ISR and an optional argument to be passed to the ISR Before assigning a new ISR the interrupt in question should be turned off using NutIrqDisable afterwards it should of course be turned on usign NutIrqEnable For external interrupts which allow monitoring the logical level of up to eight input pins INTO through INT7 we need to additionally clear its DDRx port bit to define the pin as an input pin and define for what kind of levels or level changes we want an interrupt This is done with the NutIrqSetMode function which takes an external interrupt signal and a trigger mode as input again this should be set before the input is enabled Table 10 1 summarizes the various ways the pin level can be monitored include lt dev irqreg h gt void my_interrupt6_handler void arg static u_char my_variable 0 static variables for persistance NutIrqDisable amp sig_INTERRUPT6 cbi DDRE DDE6 define pin E6 as input NutRegisterIrqHandler sig INTERRUPT6 my interrupt6 handler NULL NutIrqSetMode amp sig INTERR

An Introduction to BTnut Applications

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