JHURSAEB User Manual - DSCL
Contents
1. 1CP3 pin C7 should be set to input before calling this function Timer3 clock must be set to run using the TMR3_source functions The TOP of the Output Compare unit set by TMR3_set_mode must not equal ICP See Also TMR1 IC read Page 47 11 16 Bit Timer Counter 3 maevarmTMR3 h c 11 8 TMR3_pulsein unsigned int TMR3_pulsein Function Waits for a square pulse to occur on the Input Compare Pin 3 ICP3 and returns the length of the pulse in term of timer counts Prerequisites 1CP3 pin C7 should be set to input before calling this function Timer3 clock must be set to run using the TMR3_source functions The TOP of the Output Compare unit set by TMR3_set_mode must not equal ICP See Also TMR1_pulsein 11 9 TMR3_IC_clear char TMR3_IC_clear Function Clears the Input Capture unit event flag See Also TMR1_IC clear Page 48 12 Two Wire Interface 12C Functions maevarmTWI h c 12 Two Wire Interface 12C Functions maevarmTWI h c The TWI module uses the 12C protocol to allow serial communication with peripheral devices attached to the MaEvArM Amtel calls their 12C module TWI due to patent issues On the MaEvArM pin DO corresponds to SCL and pin D1 corresponds to SDA 12 1 TWI_enable char TWI_enable Function Enables the TWI module and have it take over pins DO SCL and D1 SDA Notes This function is NOT necessary in order to use the TWI module as calling TWI_st2. Once this function has been called pin D2 will be released and data cannot be received until USART_rx_enable is called again See Also USART rx enable Page 58 13 USART maevarmUSART h c 13 13 USART_printf int USART_printf const char fmt Function The USART_printf function works like a standard printf function The first argument should be a string with format tags inserted as desired There should be as many arguments following the first argument as there are format tags Prerequisites USART_init and USART_tx_enable must be called beforehand only once Notes Certain special characters of the character variety may not be displayed properly By default the usb_printf function cannot format floating points In order to enable the full version or the lighter version of usb_printf see Section 3 2 Linker Options Setting up your project to use usb_printf and usb_scanf and the standard C math library on Page 7 See available formats here http www cplusplus com reference clibrary cstdio printf Remember that with the LCD display you must explicitly control the cursor position with special control character sequences that are unique for each model of LCD Read the LCD manual Tips Tricks and Common Errors Students often mistakenly use the function printf as opposed to USART_printf If nothing is displaying on the terminal then this may be the reason Sample USART
3. ADC _ set channel Page 21 7 Analog to Digital Converter maevarmADC h c 7 3 ADC_set_CLK char ADC_set_CLK unsigned char ADC_CLK_SETTING Function Sets the clock source for ADC The clock speed determines the resolution and speed of A D conversions ADC_CLK_SETTING Desired prescalar clock prescaled from system clock ADC_CLK2 ADC_CLK4 ADC_CLK8 ADC_CLK16 ADC_CLK32 ADC_CLK64 ADC_CLK128 number determines prescaling factor Notes The clock speed should be between 50 200kHz for the best resolution By default the clock is set to system clock 2 See Also ADC enable 7 4 ADC_set_channel char ADC_set_channel unsigned char ADC_CHANNEL_SETTING Function Sets ADC channel to read from ADC_CHANNEL_SETTING Desired ADC channel 0 1 4 14 ADC channel and their corresponding port pins O FO 1 F1 4 F4 5 F5 6 F6 7 F7 8 D4 9 D6 10 D7 11 B4 12 B5 13 B6 14 Temperature Sensor Notes By default ADC channel O FO is selected Tips Tricks and Common Errors If you re going to be reading consecutively from one channel then there is no need to call this function every time you only need to call this when you wish to change the channel Sample ADC_set_channel 12 set to channel 12 B5 ADC_set_channel 0 set to channel O FO See Also ADC read ADC set AREF Page 22 7 Analog to Digital Converter maevarmADC h c 7 5 ADC_disable_digital char
4. www compuphase com software termite htm A light software with a simple UI Page 11 3 Creating Compiling and Running Code on the JHURSAEB MaEvArM 3 6 General Tips FAQ and Troubleshooting Do I have to create a new project or source code for each part of the lab No What you can do is rename your main function to something else such as main1 or part1 and then write a new main function for the portion of the lab you are currently working on This way you can keep all of your main functions in one source code How do power the MaEvArM When the device is connected to the computer it gets its power through the USB port so unless you want to have the MaEvArM run while detached from the computer you don t need to provide external power to the MaEvArM With the USB connected you can access the 5V line through the pin V If you do want to power the MaEvArM in other ways connect 5V to the V pin and the ground to the GND pin When can I use hexadecimal numbers and when can I use decimal To the compiler hexadecimal number with prefix Ox decimal just number octal number with prefix O and in some cases characters characters with single quotation marks around them are all the same and they are interchangeable You should use whatever makes the code easier to read or is more intuitive to you How do write a number in binary You can t Use a binary decimal hexadecimal conver
5. A OF Buin A RNN A ana 33 9 4 TMRO X valie X SArOr Baraa a E O a 34 16 Bit Timer Counter 1 MaevarMTMR1 C ccccccccccceccccccececececccececccecececueseseeuusseseessusssesesecesesess 35 TOL TMR I SOUE ds ade Cubase seen ac a a a aa a aa a O iah 36 10 2 TMRI s t mode hiari EEE OA ia 37 Page ii Contents 10 3 TMRI X mode X A Bor C niania Qedscesscvvdseeeiaeedsdudivesadsneiadeedinddtdeaddedeidocodsdnateled dadieees 38 10 4 TMR1_X valie X A B OF Citi a 39 10 5 TMR1_IC_noise canceller coccnnnnuouuoncncnnoninnnnonnononnnnnnnnnnnnnnnnnnonononnnnnnnnnnnnnnnnnnnnnnnnnnnnncnnannnns 40 10 6 TMRLAC Edge Select A A A ta 40 10 7 TMR IC read cceniscscictssiecetacveraceddivedecedaseancacidensaeavdae cateasucesntasecceundasazcesenavasdoded cendedsnandaceesaaecs 41 10 87 TMRL pUlSe ini ex a A Ake A ai a ees 42 10 9 IMRL IC cea ta a 43 11 16 Bit Timer Counter 3 maevarmTMR3 h C ooconncnononanananananananaconononcnnonononononononononononononananananannns 44 11 1 TMR3 SOU Ci adi dl 45 11 2 TMR3 Set mode lianas a taa 45 113 TMRI X model X A BOr li dadas 46 11 4 TMR3X valle X SA Bor Ci ii 46 T15 TMR3_1E noise lt cancellen ii ii a a asia aia 47 11 6 TMR3 IC Edge selec a Ad Edi 47 11 7 TMRS A E E a A dd 47 E ER O O E esse 48 11 97 IMA IES ai A AS A A EE 48 12 Two Wire Interface 12C Functions maevarmTWI h C cccceccccceesssccececsssscececessesecesesssseeceesssaees 49 121
6. ADC_disable_digital unsigned char ADC_DIGI_PIN Function Disables digital input on an ADC pin ADC_DIGI_PIN Desired pin connected channel number 0 1 4 13 ADC channel and their corresponding port pins O FO 1 F1 4 F4 5 F5 6 F6 7 F7 8 D4 9 D6 10 D7 11 B4 12 B5 13 B6 Notes Call to disable the digital input buffer on a port pin for saving power See Also IO mode ADC set channel 7 6 ADC_justify char ADC_justify char ADC_JUST_SETTING Function Justifies the results of AD conversion to the left or to the right In layman s terms within the 16 bits 2 registers containing the 10 bit ADC data the data is either aligned to the left or to the right ADC_JUST_SETTING Desired justification side ADC_LEFT ADC_RIGHT Left or right justification Notes If using ADC_read to obtain all 10 bits then justify right If using ADC_read8 to obtain only the most significant 8 bits then justify left By default the data is justified right See Also ADC read ADC readH Page 23 7 Analog to Digital Converter maevarmADC h c 7 7 ADC_read unsigned int ADC_read Function Reads and returns the 10 bit ADC value from the selected channel Prerequisites ADC must be enabled using ADC_enable Notes The 10 bits of data should be right justified before using this function or you will get a value that is multiplied by 246 6 extra bits to the side To read from a specific ch
7. Added documentation for new function USART_printf to Section 13 USART maevarmUSART h c Added documentation for new function USART_printf to Section 13 USART maevarmUSART h c 0 3 2011 09 27 Revision 19 Corrected directory typos on pages iv and 4 Example user directory corrected to read as follow in page iv and page 4 C Users Guest RSA_2011 Whitcomb My_Hello_World_Project 0 4 2012 04 11 Revision 20 Update to match library updates and explanation of JHURSAEB s soft reset button Changed font of WI u vfprintf to make lowercase L be differentiable from an upper case i Added additional explanation about usb_initialize Added TMRO and TMR3 sections 0 5 2012 06 28 Revision 22 Updated MaEvArM graphics for Rev 4 0 of the board and fixed minor typos Added note about setting up the USB Serial driver on Windows Updated links to JHURSAEB website Page v 1 Introduction 1 Introduction The JHU Robot Sensors and Actuators Education Board JHURSAEB is a microprocessor development board for use in undergraduate robotics laboratory courses at the Department of Mechanical Engineering Johns Hopkins University This board utilizes at the MaEvArM microcontroller platform developed by Prof Jonathan Fiene at the Department of Mechanical Engineering and Applied Mechanics University of Pennsylvania The MaEvArM utilizes Amtel s ATmega32U4 microcontroller The USB interface built into this microcontroller allows pr
8. TWi enable da cose A CRI a ahii 49 122 ST WI bitrate desk add 49 LL PW Si A AA A a 50 12 4 TWI tx add ss sess coscdave ccces odes isseedieeinesadivedehccdesssauveet A a e aee aaah 50 125 TWi berdatallaaia a aa id 51 126 TWE Stop A AA AA AA ETATER nea Teneo 51 A A A 52 13 USART maevarmUSART h C ccccccccccccccccccccccctcccssssssssssssssescscsceccecececcscscecesceseeeeeuecensseeesssssssscssese 53 13 1 USAR Tic a A a 53 13 2 USAR SIZE A O thas cass 54 13 3 USAR T Set parir cas 54 134 USART set oa a11 A E E O E E A es 54 RBS USART O Ea E ia ata 55 13 67 USAR TDi A A EE A EE E R amieqtaa eens 55 Page ii Contents 13 7 USARIO iii AAA Ant See 56 13 8 USART dx disable liviana dia 56 139 SUSART rx able tia 57 13 10 USART lcd AA AAA ta 57 13 11 O NN 58 13 12 USART nadia tias 58 13 13 USART Print Diada ads 59 Page iv Contents O Modification History 0 1 2011 09 14 Revision 17 First release 0 2 2011 09 20 Revision 18 0 2 1 Revised recommended user project directory to work on Windows 7 PCs in Wyman 140 This is a change to Section 3 Creating Compiling and Running Code on the JHURSAEB MaEvArM We can t use C RSA_2011 your_name to store your project files because the directory is protected Since you will be logged in as Guest store your projects in the following directory C Users Guest RSA_2011 your_name for example C Users Guest RSA_2011 Whitcomb My_Hello_World_Project 0 2 2
9. com site terminalb A simple executable terminal with the ability to scan for port This is the program we will be using in the class Running Terminal 1 Open Start gt All Programs gt Terminal 2 Connect the MaEvArM to the PC and wait for the device to be recognized 3 Make sure the settings at the top match the image below with the exception of COM Port number The MaEvArM s COM Port number will most likely be the highest numbered port If it does not show up then click ReScan to update the options COM Port Baud rate Data bits Parity Stop bits Handshaking C 600 14400 57600 Css f none e 4 none SE zj e 1200 19200 C 11520 C odd C RTS CTS COM 2400 28800 128000 C7 C even ni5 C ON OFF _CoMs C 4800 38400 C 256000 E C mark C RITS CTS ONA lt OFF 9600 lt 56000 custom 8 C space 2 C RTS onTX invert 4 Press Connect to connect to the device and begin communication 5 Make sure you press Disconnect to end communication before you disconnect the MaEvArM put it into programming mode or push the reset button on the MaEvArM otherwise the terminal will not be able to recognize the port until you press Disconnect and then reset the device This is not necessary for the B4 RST Button on the JHURSAEB 3 5 2 SerialChart http code google com p serialchart Optimized for data plotting Chart formatting is done purely through text commands 3 5 3 Termite http
10. that the user assigns to that timer module and this is used to calculate the relationship between the number of counts and the time that has elapsed Timer O is an 8 bit counter meaning that they count from a value of O to 255 For 16 bit counters use time counter 1 or 3 atmega32U4 also has timer4 but it does not have a library implementation at this time Timer 0 interacts with the following I O pins B7 TimerO Output Compare A OCOA DO TimerO Output Compare B OCOB D7 TimerO Counter Source TO Terminology TOP value that the counter counts to before overflowing BOTTOM value of O MAX highest possible value in this case 255 OCRX value stored in Output Compare Register X by function TMRO_X_value Page 31 9 8 Bit Timer Counter O maevarmTMRO h c 9 1 TMRO_source char TMRO_source unsigned char TMRO_SOURCE Function Selects the clock source for Timer 0 TMRO_SOURCE The source clock for Timer O TMRO_SOURCE_NONE No clock stops timer TMRO_SOURCE_CLK1 TMRO_SOURCE_CLK8 TMRO_SOURCE_CLK64 TMRO_SOURCE_CLK256 TMRO_SOURCE_CLK1024 System clock prescaled by number TMRO_SOURCE_EXTFALL External pin D6 counting on falling edge TMRO_SOURCE_EXTRISE External pin D6 counting on rising edge Notes By default the timer is not connected to a source clock SOURCE_NONE so this function must be called before using Timer0 Other TimerO setup functions however can be called bef
11. using USART_ init Data size must be set to 9 bits using USART_size Transmission must be enabled using USART_tx_enable Notes This function should only be used to send 9 bits of data For other data sizes see function USART_tx Sample USART_init 9600 USART_ASYNC set baud rate to 9600 asynchronous USART_size 9 set data size to 9 bits USART_tx_enable enable transmission USART_tx9 400 send decimal number 400 See Also USART tx enable USART size USART tx 13 8 USART_tx_disable char USART_tx_disable Function Disables the USART transmission unit Notes Once this function has been called pin D3 will be released and data cannot be transmitted until USART_tx_enable is called again See Also USART tx enable Page 56 13 USART maevarmUSART h c 13 9 USART_rx_enable char USART_tx_enable Function Enables the USART reception unit Notes This function must be called before receiving data This function gives the USART module control over the RXD1 pin D2 See Also USART rx USART rx9 USART rx disable 13 10 USART _rx unsigned char USART_rx Function Receives data from the RXD1 D2 pin and returns data size of 5 8 bits Prerequisites Baud rate must be set using USART_ init If receiving data with size other than 8 bits the data size must be set using USART_size Reception must be enabled using USART_rx_enable Notes This functio
12. 0 to a clock and begin PWM See Also TMRO_set_mode TMRO_source 9 4 TMRO_X_value X AorB char TMRO_X_value unsigned char COUNTER_VALUE Function Stores the comparison value for Timer0 s output compare units COUNTER_VALUE desired comparison value 0x00 OxFF Sample TMR1_A _ value 0x0F set A comparison value to 15 TMR1_B_value OxFF set B comparison value to 255 See Also TMRO_X_ mode Page 34 10 16 Bit Timer Counter 1 maevarmTMR1 h c 10 16 Bit Timer Counter 1 maevarmTMR1 h c Timers Counters are modules that can count up or down at a steady rate They can be used to measure the time between two events create a waveform or to keep track of time The counting frequency of each timer is determined by the prescaled timer that the user assigns to that timer module and this is used to calculate the relationship between the number of counts and the time that has elapsed Timer1 is a 16 bit timer while the atmega32U4 has an 8 bit CPU This means that the CPU must take a special procedure to interact with registers that contain 16 bits during which interrupts will lead to errors Therefore all functions that interact with the 16 bit registers will disable interrupts before the read write operation and will enable them once the operation is done The functionality of Timer1 is nearly identical to that of Timer3 Timer 1 interacts with the following I O pins B5 Timer1 Output C
13. 0w xX Notes The pin should be set to INPUT using 1 O_mode and the logic level written to the pin using lO_out should be LOW before using this function Sample 10_mode D2 INPUT set pin D2 to input char switch 0 allocate variable switch O_read D2 store D2 reading into switch See Also 10 mode Page 20 7 Analog to Digital Converter maevarmADC h c 7 Analog to Digital Converter maevarmADC h c ATmega32U4 contains a 10 bit analog to digital converter ADC The maximum value can be set to internal 5V internal 2 56V or an external voltage on the AR analog reference pin The minimum is always GND There are 12 ADC channels 11 ADC pins and 1 temperature sensor ADC pin and their corresponding port pins O FO 1 Fl 4 F4 5 F5 6 F6 7 F7 8 D4 9 D6 10 D7 11 B4 12 B5 13 B6 14 Temperature Sensor 7 1 ADC_enable char ADC_enable Function Enables the ADC module Notes Must be called before AD conversion can occur See Also ADC disable ADC read ADC set CLK ADC set AREF ADC set channel 7 2 ADC_set_AREF char ADC_set_AREF char ADC_AREF_SETTING Function Sets the reference maximum voltage for ADC ADC_AREF_SETTING desired reference voltage source AREF_Ext AR pin voltage AREF_Vcc Internal 5V AREF_256 Internal 2 56 V Notes By default the reference voltage is set to the AR pin See Also ADC enable
14. 1 IC clear TMR1 IC edge select IMR1 IC noise canceller Page 41 10 16 Bit Timer Counter 1 maevarmTMR1 h c 10 8 TMR1_pulsein unsigned int TMR1_pulsein Function Waits for a square pulse to occur on the Input Compare Pin 1 ICP1 and returns the length of the pulse in term of timer counts Prerequisites ICP1 pin D4 should be set to input before calling this function Timer1 clock must be set to run using the TMR1_source functions The TOP of the Output Compare unit set by TMR1_set_mode must not equal ICP Notes This function clears the event flag before reading the rising edge and therefore it is not necessary to clear the flag before calling this function The current version of this function only accounts for the possibility of a single overflow so if the duration of the pulse is large enough to cause the counter to overflow twice then the returned value will be inaccurate Tips Tricks and Common Errors If Timer1 source is set to be 1 MHz no prescaling if system clock is 1MHz divide by 8 if system clock is 8 MHz etc then the function returns the duration of the pulse in microseconds Sample TMR1_source TMR1_SOURCE_CLK1 set clock source to system clock mode_D 4 input set pin D4 to input int duration 0 initialize variable duration TMR1_pulsein measure pulse duration and store See Also TMR1 IC read TMR1 source Page 42 10 16 Bit Timer C
15. 4 2 1 Installing the Atmel Development Environment for WindoOWS cccccccnnnnnonanonnnononononnnonananananons 4 2 2 Installing the JHURSAEB and MaEvArM library and header files ococconcooonocnnononcnnnnnanannono 4 Creating Compiling and Running Code on the JHURSAEB MaEvArM ccccnnoccnccnonoonncnnnnonnnncnnnonononnn ns 4 3 1 Setting UP yo r projet iis cccccsedscackcdeasbecccchdtieecedecatsadveadvancccecusnveeaccachassaccsasdtcusdedbuddnededevaadacedessaaucel 4 3 2 Linker Options Setting up your project to use usb_printf and usb_scanf and the standard C mathllbrarY atada latina catas 7 3 3 Simple Project Source Code Example oooooooccccocccoccnnoonononnnoncnnnnnnnnnnnnnonnnnnnnnnnnnnnnnnnn corno nnnnnnnnnninnns 9 3 4 Compiling Downloading and Running Your Project ooooocccccncnnnonnonononnnoncnnnonnnnnnnnnnnnnnnnnonnnnnos 10 3 5 Serial Terminal Emulators iii AA 11 3 5 1 Terminal Recommended for this course ccocnnnonccuoooannnnnnnnnnnannonnononcnnnnnnnnnnonononnnnnnannnnnos 11 3 5 2 Serial CE ad a 11 3 5 3 MEM a di ai dias 11 3 6 General Tips FAQ and Troubleshoo0ting ccccccconnnnonoononnnononnnnnnnnnnnonnnononnnnnnnnnnnnnnnnnnnnnnnnnnnnnos 12 Using this Manual Name of Source Code and Header File ccccccnnononnononnnonnnoncnananonanononcnnnnnnos 13 USB Communication MaevarMUSB H C ccccessssssssscssscsecsccceecececececececececececeesecesuuuesaesssusesesesecesesess 14 5 1 USD
16. C Functions maevarmTWI h c 12 7 TWI_disable char TWI_disable Function Disables the TWI module and releases the pins Notes This will make pins DO and D1 behave like normal I O pins again In order to communicate using TWI again the TWI module must be enabled using TWI_enable See Also TWI_enable Page 52 13 USART maevarmUSART h c 13 USART maevarmUSART h c USART Universal Synchronous and Asynchronous serial Receiver and Transmitter is a serial communication unit with independent lines for transmitting and receiving data The data can be transmitted synchronously in sync with a clock signal or asynchronously no syncing Unlike other communication protocols USART does not require both transmission and reception lines to be connected in order to communicate instead relies on cues embedded in the protocol to let the devices know the beginning and the end of transmission The USART module in the MaEvArM utilizes TTL protocol meaning that 5V is logic 1 and OV is logic O The USART system uses pins D2 D3 and D5 on the MaEvArM D2 RXD1 Receive Data D3 TXD1 Transmit Data D5 XCK1 Clock 13 1 USART_init char USART_init unsigned int baud char setting Function Initializes USART as synchronous or asynchronous with a specific baud rate baud desired baud rate 0x0000 0xFFFF setting asynchronous or synchronous communication USART_SYNC USART_ASYNC Notes Most commonly
17. LK to 1 MHz 8 125KHz ADC_set_channel 4 set ADC channel to 4 F4 ADC justify ADC_LEFT left justify data value ADC_readH read and store value in variable See Also ADC read ADC justify 7 9 ADC_disable char ADC_disable Function Disables the ADC system Notes Once this function is called no A D conversions can occur until ADC_enable is called again Page 25 8 Serial Peripheral Interface maevarmSPI h c 8 Serial Peripheral Interface maevarmSPI h c Serial Peripheral Interface is a serial communication protocol that allows a master device to communicate with a slave device using 4 lines The 4 SPI pins on the MaEvArM are BO SS Slave Select B1 SCK Serial Clock B2 MOSI Master Out Slave In B3 MISO Master In Slave Out The ATmega32U4 can be programmed to act as a master or a slave Even when SPI is enabled the 4 pins will act like regular I O pins when data isn t being transferred This means that the user must correctly initialize the port pins to be in the correct mode and have the appropriate digital output The initialization functions will do this for you but you must make sure that you don t change the modes or the outputs of the pins in a way that will interfere with the SPI communication Communication becomes active when the master brings the SS line low The slave will communicate and receive data in sync with the SCK pulses provided by the master 8 1 SPI
18. M E 530 420 JHU Robot Sensors and Actuators Education Board JHURSAEB and MaEvArM User Manual Yonjae Kim and Louis L Whitcomb Department of Mechanical Engineering Johns Hopkins University Revision 22 July 5 2012 Download the latest version of this manual here https dscl Icsr hu edu JHURSAEB JHURSAEB MaEvArM Banana Jacks s4 pe H 091 9V Battery or Wall Plug aqold 3dOISO ISO 104 punoss 5V Regulator s4 pe H DVLf Reset Switch for USB Communication Contents Contents O Modification n Eee EEE EE EE E soos E E A sa aes diatas A E T v 0 1 2011 09 14 Revision L7 ri ii iio v 0 2 2011 09 20 Revision ii a a a aE aE v 0 2 1 Revised recommended user project directory to work on Windows 7 PCs in Wyman 140 v ray 0 2 2 Added documentation for new function USART_printf to Section 11 USART MievarmUSART A Eur A A Eo v 0 3 2011 09 27 Revision 19 Corrected directory typos on pages iv and 4 cccccccnnncononoonoannnonancnnnos v 0 4 2012 04 11 Revision 20 Update to match library updates and explanation of JHURSAEB s soft A A O A aa aaa aaa an AREG v INTO UCM A A O S 1 1 1 ROSOUNCOS ccf aaeei i aa di dada e 1 1 2 JHURSAEB Board M N WaLa ii A E A T 2 1 3 JHURSAEB Board BA RST BUTTON coccoccccnnocccanccnnnonanonancnononnnnnnnnnnnnnnnrnnnnnannn occ ae ati a a ais 3 Development Environment InstallatiON ooooooccccccnncanonanonnnonnnononnnonananono non nnnononnnonnnnnnnn nro nnnnncnncnnnnns
19. MItiAliZe A O E E AF 14 5 2 USD SPINEL deste a lA a o e Sato To 15 Page i Contents 6 7 8 9 10 5 3 A 16 General MaEvArM Functions maevarmGEN h C cocccccnnnnccnnnnnononononononononenonananannanananararararonononinnanos 17 6 1 o CENAN NT 17 6 2 O iea e O O aeaa 17 6 3 A emrine e aa a E a Ra ea A EAR 18 6 4 DE OR a AAA A Aa 19 6 5 A A RA OS 20 Analog to Digital Converter maevarmADC h C ccccnnoccccnnonononnnnooonnnnnonononannnononnnnnnnnnnnnnannnonnannnccnnnnss 21 7 1 ADC ads 21 7 2 ADC SCUSAREF ici a 21 7 3 ADC Set CU A A A AA daa dines acd 22 7 4 ADC set Channel Dani 22 7 5 ADE Sd di a a hee 23 Fibs SADC TUS Iii a A A A A eae a N 23 7 7 ADC Read 1 sw eee aioe tulsa ebsiee Gak asaaeddsDuevaeiuenoagbee oes euat aie et aeet Seeded ohn foo dace had EE O an 24 7 8 O Eee eae reece a ET 25 7 9 ADE disable iia A A nd eee ta A 25 Serial Peripheral Interface Ma VArMSPI A C cccescccceesssscececesssceceecsssecececseesecesessseecesesseseeeecseaeeess 26 8 1 SPI Masters eras aia ia caidas 26 8 2 SP data Orderiata a nea he tain eh le e es leo coa le cd 27 8 3 h E caatauvee casaabate E OAE 28 8 4 Silao anai Ata AAA ai AAA idad cea 28 8 5 SPSS ata dt ea a e aaa eh le e e es leas cool ol 29 8 6 SP iia A A da 30 8 Bit Timer Counter O maevarmTMRO h C oocccncnnnconononononcncnnononononononononenenanannnnanananararanananoneninnnnos 31 9 1 TARO QUE ira 32 9 2 TMRO s t Model A A a ea 32 9 3 TMRO X Model X
20. PIN MANIPULATION PIN NAME For multiple pin manipulation insert one of the predefined names for groups of pins ENTIREB ENTIRED pins B7 BO or D7 DO UPPERB UPPERD UPPERF pins B7 B4 D7 D4 or F7 F4 LOWERB LOWERD pins B3 B0 or D3 DO config Desired multiple pin configuration Each binary digit corresponds to a pin with the leftmost binary digit corresponding to highest pin number For example setting UPPERB to OxC binary 1100 sets pins B7 and B6 to HIGH 1 and pins B5 and B4 to LOW 0 Notes To produce digital output the pin should be set to OUTPUT using lO_mode If the pin is set to INPUT then this function will cause the pin to be pulled up if it is set HIGH and will cause it to act as a regular input pin if it is set LOW Sample single pin manipulation 10_mode B4 OUTPUT set pin B4 to output 10_out B4 HIGH output a logic 1 on B4 multiple pin manipulation 10_mode UPPERD OxF OxF binary 1111 sets pin D7 D4 to output 0xA binary 1010 sets pin D4 and D6 to input and 5 and D7 to output 1O_out UPPERD OxA See Also 10 mode Page 19 6 General MaEvArM Functions maevarmGEN h c 6 5 10_read char 10_read PIN NAME Function Returns the logic level detected on one of the I O pins PIN NAME consists of 2 arguments char let char num but macros have been set up to accept pin name e g B7 FO pin combination available 0 1 2 3 nmo
21. R3_source To generate an output the corresponding pin must be set to output using O_mode Notes Pins OC3B and OC3C do NOT exist See Also TMR1_X_ mode 11 4 TMR3_X_value X A B or C char TMR3_A_value unsigned int COUNTER_VALUE Function Stores the comparison value for Timer3 s output compare units COUNTER_VALUE desired comparison value 0x0000 0xFFFF Notes Pins OC3B and OC3C do NOT exist See Also TMR1_X value Page 46 11 16 Bit Timer Counter 3 maevarmTMR3 h c 11 5 TMR3_IC_noise_canceller char TMR3_IC_noise_canceller char setting Function Activates or deactivates the built in Input Capture noise canceller setting desired Noise Cancel setting TMR3_NC_ON noise canceller on TMR3_NC_OFF noise canceller off See Also TMR1_IC noise canceller 11 6 TMR3_IC_edge_select char TMR3_IC_edge_select char setting Function Determines whether the Input Capture Unit is triggered by a rising edge or a falling edge In other words sets the definition of an event setting desired edge selection TMR1_ES_RISING Rising edge select TMR1_ES_FALLING Falling edge select See Also TMR1_IC edge select 11 7 TMR3_IC_read unsigned int TMR3_IC_read Function Waits for a flag to be set by an event on the Input Capture pin ICP3 C7 and returns the counter value at the event After reading the value the function clears the flag Prerequisites
22. RT_tx_enable Function Enables the USART transmission unit Notes This function must be called before sending data from atmega32U4 This function gives the USART module control over the TXD1 pin D3 See Also USART tx USART tx9 USART tx disable 13 6 USART_tx char USART_tx unsigned char data Function Transmits data on TXD1 D3 pin and accepts data size of 5 8 bits data data to be transmitted Ox00 OxFF Prerequisites Baud rate must be set using USART_init If sending data with size other than 8 bits the data size must be set using USART_size Transmission must be enabled using USART_tx_enable Notes This function can send 5 8 bits of data see USART_tx9 for sending 9 bits of data but it does not check to see what the size setting is So if the size is set to 5 and you input an 8 bit data into this function then the top 3 bits will be masked and only the lower 5 bits will be sent Sample USART_init 9600 USART_ASYNC set baud rate to 9600 asynchronous USART_tx_enable enable transmission USART_tx g transmit the character g USART_tx 103 equivalent to above ASCII for g is 103 See Also USART tx enable USART tx9 Page 55 13 USART maevarmUSART h c 13 7 USART_tx9 char USART_tx9 unsigned int data Function Transmits 9 bits of data on TXD1 D3 pin data data to be transmitted 0x000 0x1FF Prerequisites Baud rate must be set
23. Timer1 s output compare units COUNTER_VALUE desired comparison value 0x0000 0xFFFF Notes This function involves writing to a 16 bit register so interrupts are disabled during a part of the function Sample TMR1_A_value OxOFFF set A comparison value to 4095 TMR1_B_value 65500 set B comparison value to 65500 TMR1_C_value 20 setC comparison value to 20 See Also TMR1 X mode Page 39 10 16 Bit Timer Counter 1 maevarmTMR1 h c 10 5 TMR1_IC_noise_canceller char TMR1_IC_noise_canceller char setting Function Activates or deactivates the built in Input Capture noise canceller setting desired Noise Cancel setting TMR1_NC_ON noise canceller on TMR1_NC_OFF noise canceller off Notes The noise canceller works by sampling the pin repeatedly and making sure that the pin remains changed for 4 counts in a row before storing the count value This causes the stored counter value to be 4 counts greater than the count corresponding to the event Tips Tricks and Common Errors If you re using the counter to store the duration difference between two events the 4 counts of difference won t matter as long as the noise canceller is either on or off for when both events occur See Also TMR1_IC read 10 6 TMR1_IC_edge_select char TMR1_IC_edge_select char setting Function Determines whether the Input Capture Unit is triggered by a rising edge or a falling edge In o
24. YY ZZZ type of waveform generated YYY TOP the value counter will count up to combination available NORMAL CTC PCPWM FPWM PCFPWM Only ZZZ 8 OxFF 9 Ox1FF 10 0x3FF ICR OCRA OCRA value stored in OCR1A ICR value stored in ICR1 Notes By default Timer1 is set to NORMAL operation Choosing a mode with ICR as the TOP will disable Input Capturing Sample TMR1_set_mode TMR1_NORMAL sets timer1 mode to normal TMR1_set_mode TMR1_PCPWM_8 sets mode to PCPWM with TOP value of OxFF TMR1_set_mode TMR1_CTC_ICR sets mode to CTC with TOP value of ICR See Also TMR1 source TMR1 X mode Page 37 10 16 Bit Timer Counter 1 maevarmTMR1 h c 10 3 TMR1_X_mode X A B or C char TMR1_X_mode unsigned char setting Function Sets the behavior of the output on the Output Compare pins OC1A B5 OC1B B6 OC1C B7 The exact effect depends on the type of waveform set by TMR1_set_mode setting The desired pin output behavior TMR1_PIN_NORMAL TMR1_PIN_TOGGLE TMR1_PIN_CLEAR TMR1_PIN_SET All waveforms NORMAL pin is disconnected and acts as regular port pin CTC Normal from X_mode mode TOGGLE pin is toggled on compare match CLEAR pin is cleared on compare match SET pin is set on compare match FPWM mode TOGGLE For A only if TOP is ICR or OCRA toggles pin output on compare match Otherwise normal pin operation CLEAR Clears pin on compare match s
25. _Masterlnit char SPI_Masterlnit Function Initializes the SPI module as the master Notes BO SS B1 SCK and B2 MOSI will be set to OUTPUT while B3 MISO is set to INPUT All four pins are set to HIGH meaning active high for BO B2 and pullup for MISO See Also SPI_data_order SPI SCK set SS low SS high Page 26 8 Serial Peripheral Interface maevarmSPI h c 8 2 SPI_data_order char SPI_data_order char SPI_DORD Function Sets the data order of SPI communication SPI_DORD Desired data order LSB_FIRST Least significant bit first MSB_FIRST Most significant bit first Notes By default the data order is set to most significant bit first See Also SPI_Masterlnit SPI_SCK_set char SPI_SCK_set char SPI_SCK_SETTING Function Sets the frequency of the SPI clock SPI_SCK_SETTING Desired prescalar SPI_SCK2 SPI_SCK4 SPI_SCK8 SPI_SCK16 SPI_SCK32 SPI_SCK64 SPI_SCK128 number determines prescaling of the CPU clock Notes By default the clock is set to CPU 4 See Also SPI_Masterlnit Page 27 8 Serial Peripheral Interface maevarmSPI h c 8 3 SS_low char SS_low Function Brings SS pin BO line low initiating SPI communication Prerequisites The MaEvArM should be initialized to act as the SPI master Notes This is functionally equivalent to calling O_out BO LOW Must be called before sending or receiving data if the MaEvArM is th
26. _Name Function s declaration argumentl Function Description of the function s functionality argumentl description of argument valid inputs for this argument numerical value if relevant descriptions if needed functions with many arguments may take different formats Argument1 Argument2 ArgumentB ArgumentC equivalent to saying there are 4 possible arguments for this parameter Argument1 Argument2 ArgumentB ArgumentC Prerequisites Minimal list of conditions that must be fulfilled before this function can be used successfully excluding the inclusion of corresponding header and source code Ifa function does not have this then it most likely means that aside from including the appropriate header and source code there are no prerequisites to using the function properly Notes Special considerations that should be taken into account when using this function Tips Tricks and Common Errors General tips to help use the function tricks to make using the function easier and common errors that people make Sample A sample code that serves as an example of how to use this function Note that this section will generally not include preprocessor directives e g include but will often contain prerequisites to using this function in a specific way If a function does not have sample code to go along with it it is because the function is either too simple to need one e g delay_ms or it
27. _init 9600 USART_ASYNC Set baut rate to 9600 USART_tx_enable enable transmission USART _printf decimal d n 77 formatting using d USART _printf 4 digit hex 04X n 77 formatting and padding using 04X Result decimal 77 4 digit hex 004D See Also USART_init USART_tx_enable Page 59
28. ample2 c ll maevarmUSB c Linker Options Libraries p os Memory Settings Wl u vfprintf External Tools J v Use WinAVR avr gec CAWInAVR 201 0011 0 bin avr gec exe Custom Options make CAWInAYR 201 0011 O utils bin make exe OK Cancel Help Figure 7 Specify Linker Options On the left under custom Compilation Options highlight Linker Options If you ve added a custom linker option for printf copy W1 u vfprint into the box next to Add Make sure to copy the phrase as is with no spaces Then click the Add button If you ve added a custom linker option for scanf copy W1 u vfscan f into the box next to Add Make sure to copy the phrase as is with no spaces Then click the Add button Once you ve done this click OK at the bottom to save your changes The compiler will now utilize the printf scanf functions that you ve specified Page 8 3 Creating Compiling and Running Code on the JHURSAEB MaEvArM 3 3 Simple Project Source Code Example The following simple source file example can be compiled in a project The project should include the following files 1 This source file 2 The library source file maevarmGEN c 3 The library source file maevarmUSB c If you use math functions such as sin and cos from the math library you will also need to specify the math lib
29. annel you must select the channel using ADC_set_channel To obtain the best resolution ADC clock speed must be set using ADC_set_CLK To set reference voltage to a specific value reference must be selected using ADC_set_AREF Sample int value 0 initialize variable ADC_enable enable ADC system ADC_set_CLK ADC_CLK8 set ADC CLK to 1 MHz 8 125KHz ADC_set_channel 4 set ADC channel to 4 F4 value ADC _read read and store value in variable See Also ADC readH ADC enable ADC set channel Page 24 7 Analog to Digital Converter maevarmADC h c 7 8 ADC_readH unsigned char ADC_readH Function Reads and returns the most significant byte of the 2 data registers Prerequisites ADC must be enabled using ADC_enable Notes To return an 8 bit data the data should be left justified using ADC justify otherwise this function will return the 2 most significant bits To read from a specific channel you must select the channel using ADC_set_channel To obtain the best resolution ADC clock speed must be set using ADC_set_CLK To set reference voltage to a specific value reference must be selected using ADC_set_AREF Tips Tricks and Common Errors If 10 bits of data is unnecessary then use this function after left justifying to obtain 8 bits of data Sample char value 0 initialize variable ADC_enable enable ADC system ADC_set_CLK ADC_CLK8 set ADC C
30. art also activates the TWI module This function should be used if you want to have the TWI module take control of the TWI pins before starting transmission or reception of data When TWI takes control of the pins they are pulled high See Also TWI bitrate TWI start TWI disable 12 2 TWI_bitrate void TWI_bitrate unsigned char TWI_BIT_RATE Function Sets the value of the bitrate register which is one of the two values that determine the frequency of SCL The other value prescale usually does not need to be changed by default 0 Notes SCL frequency CPU freq 16 2 BR 4 PS Bitrate value should be greater than 10 when operating as the master See Also TWI enable TWI start Page 49 12 Two Wire Interface 12C Functions maevarmTWI h c 12 3 TWI_start char TWI_start Function Generates the TWI start condition low SDA while SCL is high Notes Must be called before transmission of address and data See Also TWI enable TWI bitrate TWI tx address TWI stop 12 4 TWI_tx_address char TWI_tx_address unsigned char TWI_ADDRESS_BYTE Function Transfers the address byte entered as the argument TWI_ADDRESS_BYTE address byte to transmit 0x00 0xFF Prerequisites Must have started the transmission sequence using TWI_start Notes Needs to be called in order to select the peripheral device to communicate with This function is NOT equivalent to TWI_tx_data and shou
31. before continuing usb_initialize checks the connection automatically Sample usb_init initialize usb communication while usb_configured wait for initialization to complete OR usb_initialize initialize usb communication w B4 RST Rest of the code Page 14 5 USB Communication maevarmUSB h c 5 2 usb_printf char usb_printf const char fmt Function The usb_printf function works like a standard printf function The first argument should be a string with format tags inserted as desired There should be as many arguments following the first argument as there are format tags Prerequisites usb_init or usb_initialize must be called beforehand only once Notes Certain special characters of the character variety may not be displayed properly When communicating with the computer through the USB you should have measures in place to account for delay between communication initialization and activation of your terminal By default the usb_printf function cannot format floating points In order to enable the full version or the lighter version of usb_ printf see Section 3 2 Linker Options Setting up your project to use usb_printf and usb_scanf and the standard C math library on Page 7 See available formats here http www cplusplus com reference clibrary cstdio printf Tips Tricks and Common Errors Students often mistakenly use the function printf as oppo
32. does not make sense to provide a sample code with just this function setup functions usually fall into this category and its use will most likely be shown in context under a related function sample code Result If relevant necessary terminal results from above sample code will go here See Also List of functions appendices sections that are closely related or may help in understanding this function Page 13 5 USB Communication maevarmUSB h c 5 USB Communication maevarmUSB h c This is a set of source code header file that utilizes another set of code header that is provided by UPenn for use with the MaEvArM The UPenn files provide the initialization functions for setting up communication and a number of transmit and receive functions that form the basis for our usb_printf and usb_scanf function Descriptions of the UPenn USB functions along with the source code and header can be found 5 1 usb_initialize usb_init Initializes usb communication Must be called before any usb communication can take place usb_initialize Same functionality as usb_init but allows for the usage of the B4 RST button For details on using the B4 RST Button see 1 3 JHURSAEB Board B4 RST Button usb_configured Returns a non zero if usb communication has been successfully initialized returns a O otherwise Can be used to check the USB communication or to wait for communication to be established
33. e master and should be called only if MaEvArM is the master See Also SS high SPI_Masterlnit 8 4 SS_high char SS_high Function Pulls SS pin BO line high terminating SPI communication Prerequisites The MaEvArM should be initialized to act as the SPI master Notes This is functionally equivalent to calling 1O_out BO HIGH Must be called after finishing sending or receiving data if the MaEvArM is the master and should be called only if MaEvArM is the master See Also SS low SPI_Masterlnit Page 28 8 Serial Peripheral Interface maevarmSPI h c 8 5 SPI_send char SPI_send unsigned char SPI_DATA Function Sends a byte of data through SPI line SPI_DATA Byte to transfer 0x00 OxFF Prerequisites SPI should be initialized to act as a master or a slave As a master the SS line should be brought low using SS_low before sending and receiving data Notes Will pause the program until it is able to send data Asa slave it is strongly recommended that the software check to see if the master has brought the SS line low before calling this function as calling this beforehand will make the program wait indefinitely until it can send data Sample SPI_Masterlnit Initialize SPI as master Leave SPI_CLK to 1 4 of CPU clock Leave data order at MSB first SS_low bring SS line low to start SPI_send 0x88 send byte 0x88 SPI_send 0xC3 send byte OxC3 SS_h
34. ect Custom Options Figure 6 Setting Link Libraries Page 7 3 Creating Compiling and Running Code on the JHURSAEB MaEvArM Here you can choose which of the three printf scanf functions you want to use 1 By default no need to come to this menu or change anything here the printf and scanf functions can support all of the standard formats except for floating points and can print up to 255 characters 2 Recommended To use printf scanf functions that can support floating point variables and up to 65535 characters highlight libprintf_flt a or libscanf_flt a and then press Add Library gt 3 Touse printf scanf functions that are smaller than the default and have minimal functionality w basic integer amp string conversions and only conversion flags support highlight libprintf_min a or libscanf_min a and then press Add Library gt If you are not using a default option AFTER adding the custom link object you must also add libm a make sure libm a appears under the function object under Link with These Objects Lastly after adding the desired function link objects and libm a click on Custom Options to reach the window shown in Figure 7 below Samples Project Options Custom Compilation Options na gt i r i TIY All files Remove E maevarmGEN c maevarmTWi c maevarmUSART c ona maevarmSPl c maevarmADC c Include maevarmTMRO c Directories maevarmTMR1 c S
35. ert one of the predefined names for groups of pins ENTIREB ENTIRED pins B7 BO or D7 DO UPPERB UPPERD UPPERF pins B7 B4 D7 D4 or F7 F4 LOWERB LOWERD pins B3 B0 or D3 DO config Desired multiple pin configuration Each binary digit corresponds to a pin with the leftmost binary digit corresponding to highest pin number For example setting UPPERB to OxC binary 1100 sets pins B7 and B6 to OUTPUT 1 and pins B5 and B4 to INPUT 0 Notes By default the pins are set to input Every I O pin is connected to one or more functional units in the chip and many functions require the I O mode to be set to either OUTPUT or INPUT to work For example to generate a waveform using Timer1 on the Output Compare 1 B pin B6 pin B6 must be set to output beforehand Sample 10_mode BO OUTPUT sets pin BO to output 10_mode LOWERD OxA OxA binary 1010 sets pin DO and D2 to input and D1 and D3 to output See Also 10 out 10 read Page 18 6 General MaEvArM Functions maevarmGEN h c 6 4 10_out char 10_out PIN NAME unsigned char config Function Outputs a logic level on one or more of the I O pins SINGLE PIN MANIPULATION PIN NAME consists of 2 arguments char let char num but macros have been set up to accept pin name e g B7 FO pin combination available XX 0 1 2 3 B C D E F config Desired configuration LOW 0 HIGH 1 MULTIPLE
36. et pin at TOP SET Set pin on compare match clear pin at TOP PCPWM PFCPWM TOGGLE For A only if TOP is ICR or OCRA toggles pin output on compare match both rising and falling Otherwise normal pin operation CLEAR Clears pin on rising match sets on falling match SET Sets pin on rising match clears on falling match Prerequisites In order to use this function to generate a PWM signal the appropriate mode must be selected using TMR1_set_mode and the timer should set to run using TMR1_source To generate an output the corresponding pin must be set to output using lO_mode Notes For PWM mode setting the mode to CLEAR makes the comparison value proportional to duty cycle and setting the mode to SET inverts the signal See atmega32U4 manual section 14 8 for more details The TOGGLE modes can be used to create a square wave Sample TMR1_set_mode TMR1_PCPWM_8 sets mode to PCPWM with TOP value of OxFF TMR1_A_value 128 sets A comparison value to 128 TMR1_B_value 200 sets B comparison value to 200 TMR1_A_mode TMR1_PIN_SET set inverted PWM on pin OC1A TMR1_B_mode TMR1_PIN CLEAR set PWM on pin OC1B TMR1_source TMR1_SOURCE_CLK1 connect Timer1 to a clock and begin PWM See Also Page 38 10 16 Bit Timer Counter 1 maevarmTMR1 h c TMR1 set mode TMR1 source 10 4 TMR1_X_value X A B or C char TMR1_A_value unsigned int COUNTER_VALUE Function Stores the comparison value for
37. fpack struct Libraries Device atmega32u4 Y Unsigned Chars funsigned char Optimization Memory Short Enums fshort enums Create Hex File Generate Map File Generate List File Figure 3 Setting General Project Options c Click on the Include Directories tab on the left and press to add folder directory that contain custom header files in this case the RSA library directory C RSA_library d Press OK e See Figure 4 for a screen shot Page 5 3 Creating Compiling and Running Code on the JHURSAEB MaEvArM Hello_World Project Options Q a Tr General EA Include Directories r Libraries p ad Memory Settings Es Figure 4 Setting the Include Directory Options 4 On the left hand side right click on Source Files and Add Existing to include the C library files that you will use For the simple example in Section 3 the following header files are included Hinclude maevarmGEN h include the general header Hinclude maevarmUSB h include the USB header Hinclude lt math h gt include math library The first two lines reference the JHURSAEB libraries Include the source code for these libraries in your project source files list They are C RSA_library maevarmGEN c C RSA_library maevarmUSB c The third line above includes the header file math h that declares math functions such as sin and cos If you want to use
38. he delay_ms function causes the program to pause for the desired number of milliseconds DELAY_TIME Desired number of milliseconds 065535 Notes Limit is set by the size of the argument 65535 ms but accuracy may be lost with larger numbers Use this instead of _delay_ms because _delay_ms becomes inaccurate for delay times over 262 14 ms F_CPU in MHz 6 2 delay_us define delay_us DELAY_TIME Function The delay_us function causes the program to pause for the desired number of microseconds DELAY_TIME Desired number of microseconds 065535 Notes This function is simply a text macro and is equivalent to _delay_us delay_us becomes inaccurate for delay times over 768 ms F_CPU in MHz using delay_us is not recommended for generating waveforms with periods less than 100 us because instructions in between will add significant time to the period Page 17 6 General MaEvArM Functions maevarmGEN h c 6 3 10_mode char 10_mode PIN NAME unsigned char config Function Sets one or more of the I O pins to function as digital input or output SINGLE PIN MANIPULATION PIN NAME consists of 2 arguments char let char num but macros have been set up to accept pin name e g B7 FO pin combination available XX 0 1 2 3 B C D E F config Desired configuration INPUT 0 OUTPUT 1 MULTIPLE PIN MANIPULATION PIN NAME For multiple pin manipulation ins
39. icking Open Press Ctrl L or go under File and choose Load Hex File or choose from a list of Recent Hex Files a When you compile your project the Hex file containing the code will be generated under your project folder in a subdirectory called default b The name of the hex file will be something like this C RSA_2011 Your_Name Your_Project_Name default Your_Project_Name hex Press Run to download your program to the MaEvArm Making sure that the reset box is not ticked click on Start Application to run your program If you don t untick the reset box you may find that the power to your MaEvArM may oscillate Just unplug and plug in the device to fix If you want to make use of the reset button without sending the MaEvArM into programming mode then just press the button briefly instead of holding it After you run the program you can use the terminal emulator to connect to the serial USB output of your program Disconnect the terminal emulator before recompiling and downloading new code Page 10 3 Creating Compiling and Running Code on the JHURSAEB MaEvArM 3 5 Serial Terminal Emulators In order for you to communicate with MaEvArM through the USB port on your computer you need to download a program that will translate the digital data into characters on your screen There are many free programs available online and a few that are also good 3 5 1 Terminal Recommended for this course https sites google
40. igh pull SS line high to end See Also SPI_Masterlnit Page 29 8 Serial Peripheral Interface maevarmSPI h c 8 6 SPI_read unsigned char SPI_read Function Receives and returns a byte of data from the SPI line Prerequisites SPI should be initialized to act as a master or a slave As a master the SS line should be brought low using SS_ low before sending and receiving data Notes Works by sending the byte 0x00 while receiving data and will pause the program until it is able to send data Asa slave it is strongly recommended that the software check to see if the master has brought the SS line low before calling this function as calling this beforehand will make the program wait indefinitely until it can send data Sample char databyte 0 initialize variable SPI_Masterlnit Initialize SPI as master Leave SPI_CLK to 1 4 of CPU clock Leave data order at MSB first SS_low bring SS line low to start databyte SPI_read read and store byte in variable SS_high pull SS line high to end See Also SPI_Masterlnit Page 30 9 8 Bit Timer Counter O maevarmTMRO h c 9 8 Bit Timer Counter 0 maevarmTMRO h c Timers Counters are modules that can count up or down at a steady rate They can be used to measure the time between two events create a waveform or to keep track of time The counting frequency of each timer is determined by the prescaled timer
41. ld not be used to send data See Also TWI start TWI tx data Page 50 12 Two Wire Interface 12C Functions maevarmTWI h c 12 5 TWI_tx_data char TWI_tx_data unsigned char TWI_DATA_BYTE Function Transfers the data byte entered as the argument Prerequisites Must have started the transmission sequence using TWI_start Notes This function is NOT equivalent to TWI_tx_address and should not be used to send address Once the start condition has been generated and the address byte is transferred successfully this function can be called multiple times before stopping as long as the data will be valid with the peripheral device Sample TWI_start generate start condition TWI_tx_address 0x58 send address byte 0x58 TWI_tx_data 0x80 send data byte 0x80 TWI_stop generate stop condition See Also TWI start TWI tx address TWI stop 12 6 TWI_stop char TWI_stop Function Generates the stop condition SDA pulled high while SCL is high ending the transmission Prerequisites Must have started the transmission sequence using TWI_start and have sent at least one byte of data Notes MUST be called at the end of every transmission to terminate You cannot start another transmission until this function is called This does not release the TWI pins TWI module remains enabled after calling this function See Also TWI start Page 51 12 Two Wire Interface 12
42. mmon Errors MAKE SURE that append CR has been checked before sending data The dereference operator amp is needed to retrieve the pointer for most types of variables but because arrays naturally use pointers they don t require the reference operator Sample int number initialize int char street 256 initialize char array store first batch of characters as a decimal into number amp needed store second batch of characters as a string into street 8 not needed usb_scanf d s amp number street echo input usb_printf You entered d s number street Result If you enter 3400 Charles St The program will return You entered 3400 Charles St is tossed because the program was not told to store it See Also usb _ init Page 16 6 General MaEvArM Functions maevarmGEN h c 6 General MaEvArM Functions maevarmGEN h c This set of header source code provide functions that are made for general usage of the MaEvArM that is they do not fall under any particular functional modules consisting of functions that manipulate digital inputs outputs of the pins and delay functions It is highly recommended that you include this code for all of your projects as it also contains an initialization sequence that allows the MaEvArM to operate at 16 MHz without the initialization it will operate at 2 MHz 6 1 delay_ms void delay_ms int DELAY_TIME Function T
43. n can return 578 bits of data see USART_rx9 for receiving 9 bits of data but it does not check to see what the size setting is So if the size is set to 5 and you send in a signal with 8 bits then this is likely to cause errors in handling the data Sample USART_init 9600 USART_ASYNC set baud rate to 9600 asynchronous char data 0 initialize variable USART_tx_enable enable transmission data USART_rx receive and store data See Also USART rx enable USART rx9 Page 57 13 USART maevarmUSART h c 13 11 USART_rx9 unsigned int USART_rx9 Function Receives and returns 9 bits of data from the TXD1 D3 pin data data to be transmitted 0x000 0x1FF Prerequisites Baud rate must be set using USART_ init Data size must be set to 9 bits using USART_size Reception must be enabled using USART_rx_enable Notes This function should only be used to return 9 bits of data For other data sizes see function USART_rx If you send in a signal with more than 9 bits then this is likely to cause errors in handling the data Sample USART_init 9600 USART_ASYNC set baud rate to 9600 asynchronous int data 0 initialize variable USART_tx_enable enable transmission data USART_rx9 receive and store data See Also USART rx enable USART size USART rx 13 12 USART_rx_disable char USART_rx_disable Function Disables the USART reception unit Notes
44. ogramming of the device directly from a host computer via USB without the need for an external dongle but the device can also be programmed and debugged through the SPI and JTAG interface The coding of ATmega32U4 can be written in C using AVR Studio 4 and the GCC compiler Once compiled the hex file can be uploaded into the microcontroller through the USB interface using the Flip program More details on setup and starting up can be found on UPenn s MaEvArM page link below and in the Getting Started section Programming the ATmega32U4 involves manipulating individual bits in the registers to get the functions that you want The ATmega32U4 datasheet also below gives extensive explanations on the usage and functions of the different modules in the microcontroller and how to use the related registers For the purposes of the class we have made header files that will perform these register manipulations for you and they are described below 1 1 Resources Header Files source code zip The latest version is available as a zip file here https dscl lcsr jhu edu JHURSAEB MaEvArM Page at UPenn Amtel s ATmega32U4 Page Documents section contains many sample codes http www atmel com dyn products product_card asp part_id 4317 Amtel s ATmega32U4 Datasheet Provides explanation and sample codes http www atmel com dyn resources prod _documents doc7766 pdf Page 1 1 Introduction 1 2 JHURSAEB Boa
45. ompare A OC1A B6 Timer1 Output Compare B OC1B B7 Timer1 Output Compare C OC1C D4 Timer1 Input Compare Pin ICP1 D6 Timer1 Counter Source T1 Terminology TOP value that the counter counts to before overflowing BOTTOM value of O MAX highest possible value in this case 65535 ICR value stored in Input Compare Register from input compare OCRX value stored in Output Compare Register X by function TMR1_X_value Page 35 10 16 Bit Timer Counter 1 maevarmTMR1 h c 10 1 TMR1_source char TMR1_source char source Function Selects the clock source for Timer 1 source The source clock for Timer 1 TMR1_SOURCE_NONE No clock stops timer TMR1_SOURCE_CLK1 TMR1_SOURCE_CLK8 TMR1_SOURCE_CLK64 TMR1_SOURCE_CLK256 TMR1_SOURCE_CLK1024 System clock prescaled by number TMR1_SOURCE_EXTFALL External pin D6 counting on falling edge TMR1_SOURCE_EXTRISE External pin D6 counting on rising edge Notes By default the timer is not connected to a source clock SOURCE_NONE so this function must be called before using Timer1 Other Timer1 setup functions however can be called beforehand See Also TMR1 set mode TMR1_IC read Page 36 10 16 Bit Timer Counter 1 maevarmTMR1 h c 10 2 TMR1_set_mode char TMR1_set_mode char setting Function Sets the counting waveform generation mode for Timer1 setting The desired counting waveform generation setting TMR1_ZZZ_Y
46. ompare match SET Pin is set on compare match FPWM mode TOGGLE For A only if TOP is OCRA toggles pin output on compare match OCOB acts as regular port pin CLEAR Clears pin on compare match set pin at TOP SET Set pin on compare match clear pin at TOP PCPWM TOGGLE For A only if TOP is OCRA toggles pin output on compare match both rising and falling OCOB acts as regular port pin CLEAR Clears pin on rising match sets on falling match SET Sets pin on rising match clears on falling match Prerequisites In order to use this function to generate a PWM signal the appropriate mode must be selected using TMRO_set_mode and the timer should set to run using TMRO_source To generate an output the corresponding pin must be set to output using IO_mode Notes For PWM mode setting the mode to CLEAR makes the comparison value proportional to duty cycle and setting the mode to SET inverts the signal See atmega32U4 manual section 13 6 for more details Page 33 9 8 Bit Timer Counter O maevarmTMRO h c The TOGGLE modes can be used to create a square wave Sample TMRO_set_mode TMRO_PCPWM_MAX sets mode to PCPWM with TOP value of OxFF TMRO_A_value 128 sets A comparison value to 128 TMRO_B_value 200 sets B comparison value to 200 TMRO_A_mode TMRO_PIN_SET set inverted PWM on pin OCOA TMRO_B_mode TMRO_PIN_CLEAR set PWM on pin OCOB TMRO_source TMRO_SOURCE_CLK1 connect Timer
47. on 2 Development Environment Installation 2 1 Installing the Atmel Development Environment for Windows Follow the instructions on the MaEvArM web page http medesign seas upenn edu index php Guides MaEvArM starting for installation of the following software all software is free 1 AVR Studio 4 http www atmel com dyn Products tools card asp tool id 2725 2 WinAVR http winavr sourceforge net 3 Atmel Flip 3 4 3 http www atmel com dyn products tools card asp tool id 3886 4 USB Serial Communication Driver http www pjrc com teensy serial_install exe Also install this terminal emulator 5 Terminal https sites google com site terminalbpp When you plug in the MaEvArM for the first time the Add New Hardware wizard cannot usually find the driver on it s own You should point it to C Program Files Atmel Flip 3 4 3 usb 2 2 Installing the JHURSAEB and MaEvArM library and header files Download the zip file from this link https dscl Icsr hu edu JHURSAEB The file is named RSA_library_VXX zip where XX is the version number Download the latest version number Unzip the file contents and place all the files in the directory C RSA_library Note these files are already loaded on the computers in Wyman 140 3 Creating Compiling and Running Code on the JHURSAEB MaEvArM 3 1 Setting up your project Note If you re on one of the Wyman 140 computers DO NOT log in as Station x as this will cause compiler erro
48. orehand See Also IMRO set mode 9 2 TMRO_set_mode char TMRO_set_mode unsigned char TMRO_MODE Function Sets the counting waveform generation mode for TimerO TMRO_MODE The desired counting waveform generation setting TMRO_ZZZ_YYY ZZZ type of waveform generated YYY TOP the value counter will count up to combination available NORMAL CTC PCPWM FPWM Only ZZZ MAX OCRA OCRA value stored in OCROA Notes By default Timer0 is set to NORMAL operations Sample TMRO_set_mode TMRO_NORMAL sets timer1 mode to normal TMRO_set_mode TMRO_PCPWM_MAX sets mode to PCPWM with TOP value of OxFF TMRO_set_mode TMRO_CTC_OCRA sets mode to CTC with TOP value of OCRA Page 32 9 8 Bit Timer Counter O maevarmTMRO h c See Also TMRO_source TMRO_set_mode 9 3 TMRO_X_mode X A or B char TMRO_X_mode unsigned char X_MODE Function Sets the behavior of the output on the Output Compare pins OCOA B7 OCOB DO The exact effect depends on the type of waveform set by TMRO_set_mode X_MODE The desired pin output behavior TMRO_PIN_NORMAL TMRO_PIN_TOGGLE TMRO_PIN_CLEAR TMRO_PIN_SET All waveforms NORMAL Pin is disconnected and acts as regular port pin Normal mode TOGGLE Pin is toggled on compare match CLEAR Pin is cleared on compare match SET Pin is set on compare match CTC mode TOGGLE Pin is toggled on compare match CLEAR Pin is cleared on c
49. ounter 1 maevarmTMR1 h c 10 9 TMR1_IC_clear char TMR1_IC_clear Function Clears the Input Capture unit event flag Notes This function clears the flag that indicates that an event has occurred but does not erase the count value that was stored when the event occurred See Also TMR1_IC read Page 43 11 16 Bit Timer Counter 3 maevarmTMR3 h c 11 16 Bit Timer Counter 3 maevarmTMR3 h c Timer3 is a 16 bit timer that is nearly identical in function to that of Timer 1 Functions and arguments are provided below but for details on their use refer to their Timer 1 counterparts in the previous section Note that although Timer 3 has functions and registers to utilize output compare B and C the pins to interact with them do not exist The functions have been provided however because they can likely be used to generate interrupts Timer 3 interacts with the following I O pins C6 Timer3 Output Compare A OC3A C7 Timer3 Input Compare Pin ICP3 D6 Timer1 Counter Source T1 Terminology TOP value that the counter counts to before overflowing BOTTOM value of 0 MAX highest possible value in this case 65535 ICR value stored in Input Compare Register from input compare OCRX value stored in Output Compare Register X by function TMR3_X_value Page 44 11 16 Bit Timer Counter 3 maevarmTMR3 h c 11 1 TMR3_source char TMR3_source char source Function Selects the clock sou
50. rary libm a in the linker options Hinclude maevarmGEN h include the general header Hinclude maevarmUSB h include the USB header Hinclude lt math h gt include math library int main begin of main int fooi 0 declare int var fooi initialize to O usb_initialize initialize MaEvArM USB communication 1O_mode BO OUTPUT config BO pin as an OUTPUT while 1 Loop forever begin of while loop print to terminal usb_printf Hello World fooi d In fooi increment variable fooi fooi fooi 1 delay_ms 500 wait 500 ms 10_out BO HIGH set BO pin to 5V delay_ms 500 wait 500 ms 10_out BO LOW set BO pin to OV end of while loop end of main Page 9 3 Creating Compiling and Running Code on the JHURSAEB MaEvArM 3 4 Compiling Downloading and Running Your Project 9 To build your project press F7 bad or Build under the Build drop down menu Open Start gt All Programs gt Flip 3 4 3 gt Flip 3 4 3 Select the chip by clicking al and then choosing ATmega32U4 Does not need to be repeated each time the program is started unless you change it Make sure the MaEvArM is connected and is in programming mode press and hold the reset button until the green LED light up and then release then the orange LED should remain lit to indicate that the device is in programming mode Open the connection by clicking Ctrl U or S gt USB and then cl
51. rce for Timer 3 source The source clock for Timer 3 TMR3_SOURCE_NONE No clock stops timer TMR3_SOURCE_CLK1 TMR3_SOURCE_CLK8 TMR3_SOURCE_CLK64 TMR3_SOURCE_CLK256 TMR3_SOURCE_CLK1024 System clock prescaled by number TMR3_SOURCE_EXTFALL External pin D6 counting on falling edge TMR3_SOURCE_EXTRISE External pin D6 counting on rising edge See Also TMR1 source 11 2 TMR3_set_mode char TMR3_set_mode char setting Function Sets the counting waveform generation mode for Timer3 setting The desired counting waveform generation setting TMR1_ZZZ_YYY ZZZ type of waveform generated YYY TOP the value counter will count up to combination available NORMAL CTC PCPWM FPWM PCFPWM Only ZZZ 8 OxFF 9 Ox1FF 10 0x3FF ICR OCRA OCRA value stored in OCR3A ICR value stored in ICR3 See Also TMR1 set mode Page 45 11 16 Bit Timer Counter 3 maevarmTMR3 h c 11 3 TMR3_X_mode X A B or C char TMR3_X_mode unsigned char setting Function Sets the behavior of the output on the Output Compare pin OC3A C6 The exact effect depends on the type of waveform set by TMR1_set_mode setting The desired pin output behavior TMR3_PIN_NORMAL TMR3_PIN_TOGGLE TMR3_PIN_CLEAR TMR3_PIN_SET Prerequisites In order to use this function to generate a PWM signal the appropriate mode must be selected using TMR3_set_mode and the timer should set to run using TM
52. rd B4 RST Button If the function usb_initalize maevarmUSB h c is used to initialize usb connection the B4 RST button can be used to perform a soft reset This sends the program back to the line of the code where usb_initialize is called allowing users to start from the beginning of the usb interaction without disconnecting the usb terminal as opposed to when using the MaEvArM s reset switch which cuts off the usb connection The advantage of this is that there is less chance that the user will miss MaEvArM communications due to delay between initialization of connection and connection of the terminal and that it makes it easier to start from the beginning of the program CAVEATS This is not a true reset in that values of registers and variables will stay as they are when the button is pressed so the user should write the program to take this into account Also the switch is connected to B4 so the user should not utilize pin B4 if usb_initalize is called Sample Case A usb initialize lt B4 Button takes program back to here char var 0 variable initialized after usb_initialize vartt variable starts counting up from O when B4 is pressed Case B char var 0 variable initialized before usb_initialize usb initialize lt B4 Button takes program back to here var variable starts counting up whatever the value was when B4 was pressed Page 3 2 Development Environment Installati
53. rd Layout MaEvArM Banana Jacks s4 pe H C1 9V Battery or Wall Plug saqOJg ado gt s0 1 gt SO 104 puno 5V Regulator siapeaH OVLE Reset Switch for USB Communication Figure 1 JHURSAEB and MaEvArM A MaEvArM B 9V Battery Slot Converted to 5V by regulator and used to power the MaEvArM C AC Adapter Jack 6 12V DC Converted to 5V by regulator and used to power the MaEvArM D Power LED Will light up if power is being provided to the MaEvArM E B4 RST Button A USB use soft reset button See below F Jumpers If you wish to disconnect the B4 RST Button then take off the jumper and put it over only one pin G Breadboard MaEvArM Headers Use the breadboard to construct circuits The header pins to the left of the breadboard connect to pins on the MaEvArM and the 5V headers at the top right connect to the V pin of the MaEvArM Page 2 1 Introduction H JTAG Headers Allows connection of MaEvArM to JTAG dongle for in circuit debugging GND Test Points Clamp oscilloscope probes ground clamps to these to reduce some clutter J LCD Backpack Pin Connect the pins of the LCD Backpacks used in class to these headers K Banana Jacks These allow for easy connection of power from power supply using banana plugs and connect directly to corresponding header pins CAUTION The GND banana plug connects to GND of the MaEvArM so make sure you only connect GND to the pin 1 3 JHURSAEB Boa
54. rs Log in as Guest instead 1 Open Start gt All Programs gt Amtel AVR Tools gt AVR Studio 4 2 Select New Project or Open a For New Project choose BAVYRGCC set the project name and directory tick Create initial file and Create folder and press Finish not Next b Save your project in a new project directory under C Users Guest RSA_2011 your_name for example C Users Guest RSA_2011 Whitcomb My_Hello_World_Project c See Figure 2 for a careen shot Page 4 3 Creating Compiling and Running Code on the JHURSAEB MaEvArM Create new project Project type Project name Atmel AVR Assembler Hello_world SAVR GCC Create initial file Create folder Initial file HelloWorld Location CARSA_2011 Whitcomb Ld Ver 4 18 684 Show dialog at startup Finish Cancel Help Figure 2 Creating a New Project 3 Go under Project gt Configuration Options a Set frequency to 16000000 if you are not using maevarmGEN h then set it to 200000 and device to atmega32U4 b See Figure 3 for a screen shot Hello_World Project Options 7 Active Configuration w Edit Configurations SS al C Use External Makefile War General gt Include Directories Output File Name Hello_World elf k Output File Directory defaults EE la Fonny 16000000 Y Unsigned Bitfields funsigned bitfields gt s Y Pack Structure Members
55. sed to usb_printf If nothing is displaying on the terminal then this may be the reason Don t forget to utilize n or r to create line breaks or the terminal may become difficult to read Sample usb_initialize initialize usb communication while usb_configured wait for initialization to complete usb_printf Ways to print 77 n no formatting usb_printf decimal d n 77 formatting using d usb_printf 4 digit hex 04X n 77 formatting and padding using 04X Result Ways to print 77 decimal 77 4 digit hex 004D See Also usb init Page 15 5 USB Communication maevarmUSB h c 5 3 usb_scanf char usb_printf const char fmt Function Works like the standard scanf function except that it takes its input from the USB line The first argument should be a string containing format tags and the following arguments should contain pointers to the variables that you wish to store values into Prerequisites usb_init or usb_initailize should be called beforehand Notes This function looks for the carriage return CR to indicate the end of the string from the computer so it is critical that you check append CR before sending data when using this function This function will pause your program until data is available on the USB line See available formats here http cplusplus com reference clibrary cstdio scanf Tips Tricks and Co
56. ter and write it in decimal or hexadecimal or create your own header file containing text macros that will make the conversions for you get a compiler error that says unexpected EOF while looking for matching This is most likely caused by one of the directories containing the project files having a character that will confuse the compiler If you re working in the Wyman lab this most likely means that you ve logged in as Station x and the symbol is causing the error Switch user to guest or put the project files into a directory that won t contain characters that will confuse the compiler uploaded my program but it doesn t do anything and stays in programming mode This is most likely caused by not loading a hex file when you first start FLIP If you do this the FLIP loads a blank program onto the device which leaves only the bootloader in the MaEvArM causing it to constantly be in programming mode The timings of my functions are way off Under compiler options check to make sure that the clock has been set to the correct frequency of 16000000 2000000 if you don t include maevarmGEN h The terminal crashes when I try to communicate with the maevarm This may be caused by using the usb_initialize function and then setting the B4 pin to HIGH Page 12 4 Using this Manual Name of Source Code and Header File 4 Using this Manual Name of Source Code and Header File Function
57. ther words sets the definition of an event setting desired edge selection TMR1_ES_RISING Rising edge select TMR1_ES_FALLING Falling edge select Notes By default the IC unit is set to be triggered by a falling edge See Also TMR1_IC read Page 40 10 16 Bit Timer Counter 1 maevarmTMR1 h c 10 7 TMR1_IC_read unsigned int TMR1_IC_read Function Waits for a flag to be set by an event on the Input Capture pin ICP1 D4 and returns the counter value at the event After reading the value the function clears the flag Prerequisites ICP1 pin D4 should be set to input before calling this function Timer1 clock must be set to run using the TMR1_source functions The TOP of the Output Compare unit set by TMR1_set_mode must not equal ICP Notes This function waits until the flag is set and returns the store value but it does not discriminate as to when this event occurred If an event had occurred before calling this function and the flag is set it will immediately return the stored counter value Tips Tricks and Common Errors To guarantee returning of a count value of a future event call the function TMR1_IC_clear right before calling this function Sample int value 0 initialize variable TMR1_edge_select TMR1_ES_RISING select rising edge TMR1_IC_clear clear IC flag value TMR1_IC_read read and store the value See Also TMR1 source IMR
58. these math functions in your program you need to tell the linker to link the math library libm a into your program executable This is described in the next section See Figure 5 for a screen shot Page 6 3 Creating Compiling and Running Code on the JHURSAEB MaEvArM AVR Studio C RSA_2011 Whitcomb Hello_World Hello_World c B File Project Build Edit View Tools Debug Window Help AS E maevarmGEN c maevarmUSB c Header Files External Dependencies Other Files User CARSA_2011 WhitcombHello_WorldWHello_World c El Build Message 5H Find in Files 3 Breakpoints and Tracepoints ini col Figure 5 Specifying Library Source Files 3 2 Linker Options Setting up your project to use usb_printf and usb_scanf and the standard C math library Because a fully functional printf and scanf functions take a lot of memory AVR Studio offers 3 different versions of printf and scanf functions To choose between the three go to Project gt Configuration Option and then click on the Libraries button to get to the screen shown in Figure 6 below Hello_World Project Options X _ a Library Search Path XJ Include Directories Libraries Available Link Obiects Link with These Obiects libc a f Add Library gt libprintt_fit a y libm a libm a libobjc a Memory libprintf_flt a Settings libprintt_min a libscanf_fit a A libscanf_min a Add Obj
59. used baud rate is 9600 There will be a lower limit on baud rate due to the speed of the CPU speed This function DOES NOT enable transmission or reception or takes control over the I O pins Because the two functions are independent of each other and users may find themselves using one or the other enabling and disabling of transmission and reception have been separated into their own functions See Also USART tx enable USART rx enable Page 53 13 USART maevarmUSART h c 13 2 USART_size char USART_size char size Function Sets the bit size of the data to be transmitted or received size number of bits 579 Notes Because atmega32U4 has an 8 bit CPU working with 9 bit data requires extra steps Therefore make sure to use the appropriate 9 bit functions that have been written By default the data size is set to 8 See Also USART tx9 USART rx9 13 3 USART_set_parity char USART_set_parity char setting Function Sets the parity bit option setting desired parity option USART_PARITY_OFF USART_PARITY_EVEN USART_PARITY_ODD Notes By default parity bits are turned off 13 4 USART_set_stopbit char USART_set_stopbit char setting Function Sets the size of the stop bit setting desired stop bit size USART_STOPBIT1 USART_STOPBIT2 Notes By default the stop bit size is set to 1 Page 54 13 USART maevarmUSART h c 13 5 USART_tx_enable char USA
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