Easy PIC Development Kit 877A - User Manual
Contents
1. Mathematical operations can be difficult since the instruction set includes commands only for addition and subtraction and there are no hardware floating point operations If you reguire this functionality in your code there are some software emulation libraries that can be found on the microchip Webster www microchip com but they are not always easy to find Try a search for math emulation When programming in C many of the advanced math functions are available to you addwf lreg W Add the contents of W and lreg and stores the result in W Here the W register is the destination for the result of the addition as specified by the second argument to the instruction Alternatively you can specify 1reg to be the destination register by replacing W with F file addwf lreg F lreg is now the destination register 2 3 2 Flow Control You can control the flow of your program using conditional or unconditional branches Conditional branches i e btfss btfsc incfsz decfsz test the value of the operand and branch accordingly An example of an unconditional branch is the goto instruction A useful technigue to use with flow control is labeling You can label locations in your program and branch to that location using the label name For example bcf STATUS RPO Select bank 0 bc STATUS RP1 LOOP decfsz lreg F Decrement the value in the lreg register and skips the next goto LOOP instruction if th2. Easy PIC Development Board User Manual 1st Edition April 2005 How to use this manual In an effort to enable PICSTERS with the appropriate skill set needed to make this course as rewarding as possible this manual provides detailed information and walks you through the stages of developing your own codes This manual is divided into four parts There is a lot of material here but you may not use all of it for your project PARTS I The Easy Pic Development Board Design and Assembly This part introduces the features of the Easv Pic Development Board and gives some background information on its design II Getting Started Programming the PIC The second part provides you with a brief review of assembly language programming and the PIC instruction set Here you will find a template that you can use as a starting point for writing your own assembly language program This part concludes with instructions on assembling your assembly language program and downloading object code to the PIC microcontroller III BootLoader This part describes how the actual user codes work with the bootloader This will explain how to load the bootloader program and how to load the user code on the bootloader IV The Easy Pic Development Board In Action This part contains the information you need to make your Easy Pic Development Board actually do something It begins by introducing the operation of the Easy Pic Development Board in t
3. Diodes D1 and D2 provide some reverse polarity protection and power supply transient isolation Capacitors CI and C2 provide power supply bulk charge storage while C3 C6 provide additional power supply transient isolation for their respective supplies ICI 7805 regulates the bulk supply to the 5 Vdc needed for the PIC micro controller and logic devices logic side of MAX232 LCD 7Seg Display etc IC2 7812 and its components regulate the bulk supply for the Relay You will notice that the polarized capacitors have a non polarized capacitor in parallel with them This is not always necessary in designs but is here The reasoning is that real capacitors are not ideal capacitors larger capacitors tend to have greater amounts of intrinsic inductance associated with them due to their construction Their greater inductance gives them poorer high frequency performance Smaller capacitors tend to have better high frequency performance Therefore multiple real capacitors are used to approximate the required ideal capacitor performance 1 2 2 RS 232 Serial Interface The RS 232 circuitry consists of a DB9 female connector the MAX232 and related circuitry The DB9 connector is configured for an IBM PC style 9 pin RS 232 connection The MAX232 converts the RS 232 sometimes called the HIN232 12V signals to logic levels for the micro controller The resistors 330Q limit line slew rates and provide some short circuit protection The resistors R23 R2
4. 5 5 Kev Switches Key Switches are multiplexed with 7segment devices Key switches are connected from RBO RB5 You can use this key switches after changing the jumper to key position See the Board Program which uses the Key Switches Assembly File Hex File RBOinterrupt Example RBOInterrupt asm RBOinterrupt Example RBOinterrupt HEX stopwatch Example StopWatch asm Stopwatch Example StopWatch HEX Scanning c Example AdcScan c Scanning hex Example AdcScan HEX 5 6 Analog to Digital Converter The PIC 16F877A has 8 channels 10bit Analog to Digital Converter These eight channels are multiplexed together the ADC can only sample one input at a time Here Port A has five channels and Port E has remaining 3 channels But in this board Port E pins are used for some other purposes so you can use only PortA analog pins In this board 3 channels are directly connected with internal circuit Power through a Variable POT The POT is used to change the analog input voltage given to the pin The other two channels are used to scan the external analog inputs You should take care about the external input its range should be in between 0 5V DC The entire ADC pins have a limited amount of diode protection to prevent input voltages outside of the Vdd to Vss range A better way to make sure your PIC doesn t get fried by stray analog voltages though is to set up a small circuit before the signal rea
5. 7 Pulse Width Modulation 5 8 Relay 5 9 Buzzer 5 10 Master Synchronous Serial Port MSSP 5 10 1 Serial Peripheral Interface SPI 5 10 2 I2C 5 11 Universal Synchronous Asynchronous Receiver Transmitter USART 5 12 Timer Modules Part V How to use the Easy Pic Development Board Part I The Easv Pic Development Board Design and Assembly 1 0 Introduction to the Easy Pic Development Board The Easy Pic Development Board is a compact low power controller board that is based on the MicroChip Technologies This Easy Pic Development Board has a PIC16F877Aseries microcontroller The PIC is the heart and soul of the Easy Pic Development Board containing the central processing unit for the board The Easy Pic Development Board will be common to all projects with the addition of student designed and built circuits This Easy Pic Development Board comes loaded with the following features Communication Interfaces RS 232 communication with a PC SPI and EC busses for communicating with other chips and standard 5V CMOS digital I O for anything else The PIC16F877A Easy Pic Development Board supports Parallel Slave Port Communication Extra Features Three timer modules a multi channel analog to digital converter two pulse width modulated outputs LCD Device 7Segment Led Kev Switches Relav Buzzer and Led Additional Features of the PIC16F877 Easv Pic Development Board Bootloader that allows you to develop
6. PR2 holds an 8 bit number and TMR2 prescale value can be eitherl 4 or 16 TMR2 prescale value is set using the T2CKSP1 T2CKSPO bits T2CON lt 1 0 gt See section 7 0 Register 7 1 in the PIC16F87X data sheet Tosc is the oscillator period 0 25 us For example if PR2 contains B 01100111 103 and T2CKSP1 T2CKSPO B 01 prescale 4 then the PWM period is 103 1 4 0 25 4 416 us The duty cycles are specified with a 10 bit number Each PWM pin has an associated CCPRxL register and CCPxCON register The CCPRIL register holds the upper 8 bits of the duty cycle value for CCP1 and CCP1CON lt 5 4 gt holds the lower 2 bits For CCP2 the CCPR2L and CCP2CON registers are used The following eguation defines the PWM duty cycle For example if CCPR1L contains B 00110011 and CCP1CON lt 5 4 gt contains B 10 the duty cycle for CCPI is 206 0 25 4 206 us Program which use the PWM Assembly File Hex File Pwm asm Example Pwm asm Pwm hex Example Pwm HEX 5 8 Relay The PIC has a 25mA current drive capabilitv and this current is guite good for most low power circuits Sometimes a component like a motor or light bulb may need to be controlled by a PIC output pin and more than likely these types of components will draw more than 25mA which can be supplied by the PIC pin Figure Relay One way around this problem is to use a relay to switch the high currents needed In some cases a relay can be c
7. and load your own code to the PIC without the need of Programmer Two Methods to load the user program to the PIC BootLoader mode BootLoader Mode is very useful for code development Here Bootloader is used to load your code to the PIC Programmer mode Programmer mode uses assembly code you have written and then burned to the PIC This mode uses Programmer Complete with a relatively powerful processor and large I O capability the Easy Pic Development Board is an impressive control system The range of projects is virtually limitless you can control robots perform wireless communication carry out digital signal processing or even connect your Easy Pic Development Board to the Internet The only limit is your imagination Peripheral Features OO 1 VO Ports 2 LED 3 7Segment LED 4 LCD Device 5 Key Switches 6 10bit Analog to Digital Converter 7 Pulse Width Modulation 8 Relay Operation 9 Buzzer 10 SPI Communication 11 I2C Communication 12 USART 13 Timer Modules 1 1 Easy Pic Development Board Specifications These table lists the electrical characteristics of the Easy Pic Development Board exceeding maximum values will very quickly damage your board PIC16F877A Total Number of Pins on PIC DIP package 40 Range of Input Voltage to Barrel Connector 6 18 Vde 5 Vde PIC Supply Voltage 4 MHz Upgradeable to 20 MHz Clock Speed Digital I O P
8. determine through status bits which subsystem generated the interrupts 2 Context of the CPU is not saved except for the return Program Counter Your ISR must be written to compensate for this 3 Each interrupt uses one internal stack location until processing is complete Only 8 stack locations are available and subroutine calls also use them Due to this limitation use of nested interrupts is discouraged However nesting is disabled by default 2 6 Putting It All Together Now you are almost ready to write our own PIC assembly program You can use any text editor to write your source code as long as you save it with a asm extension It is recommended that you use MPLAB a free program provided by Microchip to write and compile your source code You can download a copy of MPLAB from the Microchip website www microchip com Below is a very simple program that is used to show the necessary components for an assembly program Also MPLAB contains source code templates f873temp asm and f877temp asm which can be found in mplab template code You can use these as a starting point ge ee KKK KK ske ske ske sie sk kokos ske k kikikikikkkkkkikikikkkkkkkikkkkkkkkkikkkikkkkkkkkk This is a program header Here you give a brief description of what your program does and any other important information about it You should include the name of the program your name the date you wrote the program and or the last date it was
9. program to the PIC These are Bootloader mode programmer mode Bootloader mode is explained in the next Section In this section you will see the Programmer mode You should buy any programmer to burn your program to the PIC Before using the Programmer you should read the manual given with it The manual describes how to put the PIC on the Socket The position where you place the PIC is very important If you do anything wrong that will permanently damage your Programmer and destroys your PIC They will provide the user friendly software to do the following Select the PIC to burn Select the hex file Configure the PIC Erase the codes in the PIC Read the PIC Burn the program to the PIC VVVVVV Using the software burn the program to the PIC You will receive a message notifying you if the program was transferred to the PIC successfully Take the PIC out of the Programmer plug it backs into your Easy Pic Development Board and you re ready for business Part III PIC 16F8xx Boot Loader 4 0 Introduction A bootloader is used to guickly download a new program into your PIC micro in a few seconds Once you have it set up you can guickly update the hex file in your PIC micro with a single keystroke Bootloading is easily performed in circuit with the PIC micro still plugged into your PCB BootLoader reserves top 255bytes in the Program memory If you use this bootloader you can t use the upper
10. 255 bytes for your normal program As well as you should also include the following four additional lines in your assembly program Org Movlw Movwf Goto Nop Org Goto Main Isev End 0x0000 These four lines should be included 0x00 PCLATH Main 0x0004 Optional Isev For CCS C language you don t need to include any additional lines 4 1 How to use the BootLoader e The PIC 16F877A that we have given to you has already programmed with the bootloader code If any case it lost load bootloader hex file to the PIC For this purpose you should use any programmer the below figure Set baud rate is 9600 to the PIC Put that PIC on the Zip Socket on the given board Plug in the RS232 serial adapter to your Board Give the power supply to the board Use MPLAB for your code creation and corrections Compile with MPLAB to produce Hex file If finished open PIC Bootloader Software BootL Sw PICbootPlus exe That window is look like Select the Com Port which will be used you will need one free com port on your system Click the search button to select your hex file Click Write button on the window software then press the reset key on the board to burn your hex file If everything is ok you will see the OK message in the info box e The bootloader remains active for 0 2 seconds after reset to give you the option of uploading new code and after 0 2 seconds or uploading complete you can use the serial port
11. 4 not shown here see Appendix A Easy Pic Development Board Schematic Diagrams R33 and R34 provide output contention protection contention is created if the Digital I O pin of PIC incorrectly configured as an output and is connected to the output of the MAX232 C24 C25 are used by the on board charge pump note that the supply is 5V and yet the IC can deliver RS 232 level signals TIOUT TIIN i pa T20UT T2IN R1IN R1IOUT R2IN R2OUT OBASF Figure 1 3 RS 232 Serial Interface Schematic Part Il Getting Started Programming the PIC 2 0 Programming the PIC Microcontroller The main focus of this manual is assembly language programming of the PIC microcontroller You will have access to a C compiler in your lab however the discussion on programming the PIC in C is limited and you will likely need to seek other resources 2 1 Assembly Language Programming Here we will review some of the basics of assembly language programming First it is important to understand the memory structure of the PIC16F877A microcontroller For detailed information on memory structure see the PIC16F877A data sheet 2 2 Memory Structure There are three memory blocks Program memory Data memory EEPROM data memory 1 Program Memory The program memory is as you may have guessed the section where your program instructions are stored The size of the program memory for the PIC16F87
12. 7A is 8Kx14 which means that it can hold 8x 1024 8192 14 bit instructions The program memory is divided into 2K blocks called pages So it has 4 pages In order for commands on a certain program memory page to be executed the corresponding page must be selected To switch between program memory pages use the pagesel directive A recommended way to use the pagesel directive is to first define the following values at the beginning of your assembly language program as follows also see section 3 6 page0 EQU 0x0000 pagel EQU 0x0800 page2 EQU 0x1000 page3 EQU 0x1800 start address of pageo start address of pagel start address of page2 start address of page3 1 Then to select a page say page 2 for example use the following in the body of your main program pagesel page2 selects program memory page 2 2 Data Memory The data memory is divided up into 4 banks bank 0 bank 3 that contain both Special Function Registers and General Function Registers The special function registers are named and have a predefined function They are used for controlling the operation of the microcontroller General function registers are used for data storage The PIC16F877A has 368 8 bit general function registers To access a register in a certain data memory bank you must ensure that the appropriate bank is selected The status of the bank select bits RPO and RPI located in the STATUS register determine which data memory bank is active For ex
13. MCP3202 is a 12 bit analog to digital converter There are two input channels available on the MCP3202 Both the inputs are multiplexed together the ADC can read only one input at a time Using the SPI MCP3202 is connected to PIC16F877A Pin Diagram of MCP3202 and Function of each pin is as follows CS SHDN VDD CHO CLK MCP3202 CH1 DOUT SS DIN Figure 6 2 MCP3202 Pin Diagram PIN FUNCTION TABLE 42 7V to 5 5V Power Supply and Reference Voltage Input Channel 0 Analog Input Channel 1 Analog Input Serial Clock Serial Data In Serial Data Out Chip Select Shutdown Input Figure 6 3 MCP3202 Pin Function Table Consider the following schematic PIC16F87X ANALOG I P 0 ANALOG I P 1 MCP3202 Figure 6 4 Schematic External ADC Using SPI The above schematic explains how to connect the external peripheral to the PIC You should read the datasheet for peripheral before using it Programs which use the SPI Function Assembly File Hex File Adc Example ExternalAdc asm Adc Example ExternalAdc HEX 5 10 2 I2C The MSSP module in I2C mode fully implements all master and slave functions including general call support and provides interrupts on START and STOP bits in hardware to determine a free bus multi master function The MSSP module implements the standard mode specifications as well as 7 bit and 10 bit addressing Two pins are
14. PO and RPI bits are used to select the data memory bank The instructions above will select bank 1 i e RB0 RB1 01 The following is an example of a byte oriented instruction clrf STATUS Clear the entire STATUS register Many instructions use the W register which you can think of as a temporary storage place To store a value in one of the general purpose registers say at address 0x20 in bank 0 you could use the following commands bef STATUS RPO select bank 0 bef STATUS RP1 movlw 0x35 writes 0x35 to the W register movwf 0x20 moves the value from the W register to the general purpose register at address 0x20 To make your code more readable you can define labels to replace numerical values These labels are defined at the beginning of your program using the EQU eguate assembler directive length EQU 0x35 Eguate the label length with value 0x35 lreg EQU 0x20 Equate the label lreg with value 0x20 With these defined the above instructions could now be replaced with movlw length Load the W register with the value 0x35 movwf lreg Move the value from the W register to the General purpose register at address 0x20 An additional benefit to using labels is that if you decide to change any one of the values in your source code you need to only change the value of the label rather than having to search through your entire source code for every occurrence of that value 2 3 1 Mathematical Operations
15. ample to access the general purpose register at address 0xA0 you must select bank 1 i e RP1 RPO 01 The banksel directive can also be used to select the desired data memory bank similar to the way in which the pagesel command is used to select the desired program memory page First define the following values BANKO EQU 0x0000 Data Memorv start positions BANKI EQU 0x0080 BANK2 EQU 0x0100 BANK3 EQU 0x0180 Then to select the bank say bankl for example use the following in the body of your main program banksel BANKI select data memory bank 1 3 EEPROM Memory The EEPROM memory is nonvolatile meaning its contents are not erased when you turn off the power to the PIC This is useful for storing information such as the state of your system before it is powered down since this information can then be retrieved when the system is powered up again Data stored in the Data memory section RAM is erased when the power is removed from the PIC 2 3 Instruction Set The PIC16F877A uses a RISC based architecture with only 35 instructions See the PIC16F877A data sheet for instruction descriptions Some of the more common instructions will be reviewed here An instruction is either byte oriented or bit oriented The following bits of a register bef STATUS RPO Clear the RPO bit in the STATUS register bsf STATUS RP1 Set the RP1 bit in the STATUS register Anything after a semicolon is a comment Remember that the R
16. as normal and also it executes the user code e Ifnot it will display the relevant error message 1 PIC Bootloader es com z 1320 2 7 1 Figure BootLoader Part IV The Easy Pic Development Board in Action 5 0 Peripheral Features This section will explain the features of the Easv Pic Development Board It has following features 1 VO Ports 2 LED 3 7Segment LED 4 LCD Device 5 Key Switches 6 10bit Analog to Digital Converter 7 Pulse Width Modulation 8 Relay Operation 9 Buzzer 10 SPI Communication 11 I2C Communication 12 USART 13 Timer Modules 5 1 VO Ports The PIC16F877 has 33 I O pins divided into 5 ports Port A Port E which can be configured in various ways to communicate with many different peripheral devices Port A has 6 pins Port B Port D each have 8 pins and Port E has 3 pins Many of these pins are multiplexed with more than one function You can control the function of each pin or group of pins by writing the proper value to the appropriate Special Function Register The simplest function for these pins is general purpose digital I O You can configure any pin as a digital output and set its value high 5V or low OV or configure it as a digital input and read its present value Each port has an associated PORTx register bi directional port and a TRISx register data direction register Setting a bit in the TRISx register makes the
17. ches the ADC pin similar to the one to the right This circuit will not let any voltage hit the ADC pin unless it is between 0 and 5V and doesn t depend on the PIC s limited protection The PIC16F877A data sheet also recommends that the maximum input impedance of an analog source be less than 10kQ and that any current on any pin should not exceed 20mA ADC converts the given analog inputs to the 10bit digital output It is stored in the register ADRESH ADRESL This conversion uses TRISA PORTA ADCONO and ADCONI register Refer 16F877A datasheet for further need ADC line 1kb2 PIC 16F877A 1 MicroBoard i DP Program which uses the ADC Assembly File Hex File Adc asm Example A dc asm Adc hex Exampletadc HEX Acd led c ExamplelAdc Led c Acd led hex Scanning c Example AdcScan c Scanning hex Example AdcScan HEX Relay asm Example Relay asm Relay hex Example Relay HEX Adc volt Example Adc_volt asm Ade volt Example Adc volt HEX 5 7 Pulse Width Modulation You can think of the Pulse Width Modulator as a square wave generator where the period and duty cycle are variable There are 2 PWM outputs CCP1 and CCP2 and they may have different duty cycles but they share a common period The PWM period is calculated using the following formula You have control over the value in the PR2 register Timer2 module s register and the TMR2 prescale value
18. corresponding pin an input clearing the bit makes it an output For example setting bit 4 in the TRISB register makes pin RB4 an input Setting a bit in the PORTx register sets the corresponding pin high as long as it is configured as an output Clearing the bit set the pin low For example setting bit 3 in the PORTC register sets the output pin RC3 high Data is input by reading from the PORTx register The following code is an example of how to implement this in your program bsf STATUS RPO select bank bcf STATUS RPl mov lw B 11110000 configure RB7 RB4 as inputs movwf TRISB configure RB3 RBO as outputs bcf STATUS RPO select banko movf PORTB W reads inputs and stores in W register movlw B 1010 sets outputs RB3 and RB1 high movwf PORTB RB2 and RBO low Each port and the alternate function s of its pins is discussed in its own section below Refer to section 3 0 of the PIC16F87X data sheet for additional information on I O ports 5 1 1 Port A In this section port A is discussed It is multiplexed with analog inputs with the exception of pin RA4 which is multiplexed with the Timer0 module Instead of Port A Port E is also multiplexed with analog inputs but in this board these pins are used to control Relays and Buzzer So you have only 5 analog channel instead of 8 In these five channels 3 channels are connected internally and analog voltage is controlled through POT The remaining two chan
19. e result is 0 goto ZERO Branch to LOOP if result not 0 branch to ZERO if result is 0 ZERO instructions 2 4 Subroutines Using subroutines is a way to make your program modular It also shortens the length of your main program making it easier to follow You can think of subroutines as mini programs that are called from the main program Subroutines are usually defined after the main program Consider the code below main main program instructions call incW call incW subroutine goto main return to beginning of main program subroutines are declared here incW incf W increment the value in the W register 3 times incf W incf W return return to main program Here a subroutine called incf W is defined The purpose of the subroutine is to increment the value in the W register 3 times In the main program you call the subroutine using the call instruction with the subroutine name as the operand When the call command is executed the main program jumps to the incf W subroutine executes the commands defined there then returns to the main program when the return instruction is executed Unlike many other microcontrollers the PIC contains no user accessible stack Adding the fact that the programmer s model contains only one working register subroutines passing more than a single byte need to make use of the file register memory Additionally the stack in the PIC16F877a devices is only 8 locations deep R
20. e your initial circuit designs on this Easy Pic Development Board then later transfer your design to a PCB CAD to have it milled into a clean PCB In general rats nests of wires don t hold up very well and in accordance with Murphy s Law will inevitably let you down when you need them the most during demonstrations of coursel Contributors This document was created bv contributions from Advanced Embedding and Packing solutions Pvt Ltd Future Tecknics Pvt Ltd and Winnii Solutions Pvt Ltd Chennai Table of Contents Part I The Easy Pic Development Board Design and Assembly 1 0 Introduction to the Easy Pic Development Board 1 1 Easy Pic Development Board Specifications 1 2 Functional Description 1 2 1 DC Power Supplies 1 2 2 RS 232 Serial Interface Part II Getting Started Programming the PIC 2 0 Programming the PIC Microcontroller 2 1 Assembly Language Programming 2 2 Memory Structure 2 3 Instruction Set 2 3 1 Mathematical Operations 2 3 2 Flow Control 2 4 Subroutines 2 5 Interrupts 2 6 Putting It All Together 3 0 Assembling Your PIC Program 3 1 Developing your PIC program 3 2 Writing Your Program to the PIC Part III BootLoader 4 1 Introduction 4 2 How to use the bootloader Part IV Easy Pic Development Board In action 5 0 Peripheral Features 5 1 VO Ports PortA B C D E 5 2 Led 5 3 7Segment 5 4 LCD Device 5 5 Key Switches 5 6 Analog to Digital Converter 5
21. ecursive calling is thereby discouraged Interrupts described next also reguire stack locations and reduce the possible call depth 2 5 Interrupts Interrupts are an alternative to polling for events and can make processing time more efficient since your program doesn t need to wait for selected events to occur by polling Every time a selected event triggers an interrupt the PIC stops execution of the program and jumps to the interrupt service routine Once finished the PIC resumes normal execution of your program where it left off Each of the built in modules has the ability to cause an interrupt for one reason or another The ADC for example can cause an interrupt when it has completed a conversion while the UART can produce an interrupt when its transmit buffer is empty or when its receive buffer is full When an interrupt occurs the PIC jumps to the program memory location 0x0004 the interrupt vector The program space available in this location is very limited so it s recommended that you place your interrupt service routine ISR elsewhere in program memory and just put a GOTO command in the interrupt vector space For Ex ORG 0X0000 Goto Start ORG 0X0004 Goto Isev Start Write your codes here Isev Write your Interrupt subroutine here End Compared with other microcontrollers the PIC16F877A family has a few notable differences with respect to interrupt processing 1 Only one interrupt vector is used Your ISR must
22. f PCLATH goto Main nop S 0x20 0x21 0x0000 0x0080 0x0100 0x0180 Data Memory start positions for use with banksel directive see section 3 2 program memory start positions for use with pagesel directive see section 3 2 where your program code begins when the PIC is powered up or after a reset the instruction at address 0x00 is the first to be executed The ORG instruction tells the device programming the PIC to start writing the following instructions at the address indicated in this case at address 0x00 selects page0 of the program memory jumps to beginning of your program Only include this next section if you are using interrupts ORG 0x04 when an interrupt occurs the program jumps to the instruction at address 0x04 jumps to the subroutine service which will handle the interrupt goto Service i this is the start of your main program Main the instructions for your main program go here this is the interrupt service routine Service the instructions for your interrupt service routine go here END this is the end of the program The source code for some example programs is available on the CD Disk It may help to take a quick look at the code to become more familiar with the contents of an assembly language program 3 0 Assembling Your PIC Program It has the following two parts 3 1 Developing Your PIC Program O To actually make your Easy Pic Developme
23. ins 33 Analog to Digital Channels 8 multiplexed Pulse Width Modulated Pins 2 10 Pin LCD Interface Yes Power Consumption with all IC s 140 mA 8 16 Vdc Max current drawn from 12Vdc connector 500 mA Max current drawn from 5Vdc connector 500 mA 50 mA Max current drawn from 12Vdc connector Table 1 1 Easy Pic Development Board Specifications 1 2 Functional Description The Easy Pic Development Board is designed in a modular manner as shown in the block diagram below Refer to the Easy Pic Development Board schematic and board layout diagrams found in appendix as necessary to improve your understanding PIC16FS77A Digital Interface Support amp Micro Controller H bridge Drivers Analog Digital Interface Support DC Power Supplies u g Analog Supply Inverter Figure 1 1 Block Diagram of the Easy Pic Development Board Design 1 2 1 DC Power Supplies 2999909 A o am sm A A l te eD z as am ao ee zm e V E sl A da mm m sm m Figure 1 2 DC Power Supplies Schematic DC power is supplied to the board through a 2 1mm coaxial barrel connector with center positive polaritv Normally this power comes from a 18Vdc 500mA wall adaptor plugged into the barrel connector However a I2Vdc LA wall adaptor or suitably sized battery array can also be used The Body or the barrel is negative supply
24. ith PORTD In this board PORTD is multiplexed with LCD Device and 7Segment LED LCD Device uses RDO RD6 pins RDO RD3 gt Control Lines Rs Rw and Es RD4 RD6 gt Data Lines Here this board has multiplexed six 7segment LED This uses Port D for data line and Port B for segment selection Data is read from written to Port D using the PORTD port register The data direction register is TRISD 5 1 5 Port E Port E is multiplexed with analog input But here these pins are dedicated to some other application like Relay operation REO RE1 and Buzzer RE2 Data is read from written to Port D using the PORTD port register The data direction register is TRISD Table 6 4 Summary of Registers Associated with PORTE Mame Add ss Bi pits its pra Bis miz BRL Biro Forte OT ner nes Res Rea Res RE Rei Reo TRISE oxe9 mr opr IBOV PSPMODE PORTE data direction bits 5 2 LED In this board Led is connected in Port B LED is used to indicate the pin status There is a Jumper to enable or diable the Led s Program which uses the LED function Assembly File Hex File Flash asm Example Flash asm Flash hex Example flash HEX Shifting asm Example Shifting asm Shifting hex Example shifting HEX 5 3 7Segment LED Here we have six 7Segment Led These are multiplexed with one another This function uses Port D and Port B Port D is used to send the data to
25. lex svnchronous system that can communicate with peripheral devices such as A D or D A integrated circuits serial EEPROMs etc The USART can be configured in the following modes Asynchronous full duplex Synchronous Master half duplex Synchronous Slave half duplex Bit SPEN RCSTA lt 7 gt and bits TRISC lt 7 6 gt have to be set in order to configure pins RC6 TX CK and RC7 RX DT as the Universal Synchronous Asynchronous Receiver Transmitter The USART module also has a multi processor communication capability using 9 bit address detection Program which use the USART Function Assembly File Hex File Usart asm Example Usart asm Usart hex Example Usart HEX In this example the USART module will be used to communicate with a personal computer HyperTerminal or other terminal program on your PC is used to communicate with the Easy Pic Development Board Easy Pic Development Board is connected using a computer serial cable The male end of the cable connects to the DB 9 connector on your Easy Pic Development Board and the female end connects to one of the serial connectors COM1 or COM2 on the back of your PC To properly communicate both the HyperTerminal and the USART must be configured with the same settings The below example program uses 9600 baud rate The mode of communication is Asynchronous since there is no clock signal Instead start and stop bits are used When asynchronous m
26. modified Include a course name if applicable name example asm date 9 July 2002 created by Murali course EEE program name that s me This program doesn t do anything since there are no instructions in the main program It is just used to illustrate the necessary components of an assembly language program for the PIC microcontroller date created ki pk kk kk kk ki ikikkkkkkkkikikikkkkkkikkikkkkkkkkikikkkkkkkkikikikkkkkkkkk list p 16f877 this tells MPLAB which PIC microcontroller you are using use p 16 877 when necessary Hinclude lt pl6f877 inc gt this file defines the names and locations of all the Special Function Registers i e W register use pl6f877 inc when necessary The following commands set the PIC s configuration bits For now you don t really need to understand how the configuration bits affect anything PIC16F87X data sheet You can also set the configuration bits manually when you are downloading your program to the PIC see section 4 1 but if you really want to see section 12 1 in the CONFIG CP OFF WDT OFF amp BODEN OFF PWRTE OFF amp XT OSC 6 WRT ENABLE ON LVP OFF amp CPD OFF Label Definition TEMP1 EQU TEMP2 EQU BANKO EQU BANKI EQU BANK2 EQU BANK3 EQU page EQU 0x0000 pagel EQU 0x0800 page2 EOU 0x1000 page3 EQU 0x1800 This is ORG 0x00 movlw 0x00 movw
27. nels is used for the external analog input The function of each pin in this port is selected using the A D port configuration control bits the lower four bits of the ADCONI register Refer to Section 11 0 Register 11 2 in the PIC16F877A data sheet for a table of the A D port configuration control bits For example to configure all the pins in ports A and E for general purpose digital I O you must write B 011x B 0110 or B 0111 to the lower four bits of the ADCONI register The analog inputs are used with the Analog to Digital Converter A D module See section 6 7 for instructions on using the A D module The ADON bit ADCONO lt 0 gt controls whether or not the A D module is operating If you are not using the A D module then it is recommended that you turn it off by clearing the ADON bit Data is read from written to ports A and E using the PORTA and PORTE port registers respectively The data direction registers are TRISA and TRISE Name Adies Bit pits Bas Bra Bas siz Bil sro l ma o ii FETA rana ara Table 6 1 nannies of Registers Associated with PORTA The following code shows how ports A can be initialized for digital I O bef STATUS RPO select banko bc STATUS RP1 clrf PORTA clear ports A to initialize bsf STATUS RPO select bank bef STATUS RP1 movlw b 0110 configure ports A and E for movwf ADCON1 digital I O movlw b 111000 set RA5 RA3 and REO as in
28. nt Board do anything it needs to be running a program In this section you will use MPLAB to develop your own assembly code In the next section you will burn the program s object code to your Easy Pic Development Board To develop and assemble the program follow these steps Open MPLAB Create New Project Project gt New Create New File File gt New Write Your assembly code Add your source code to the Project Project Add files to project Compile your source code Project gt Build All DA a o ES And that s it A new window will open that shows the results of the process If your source code is error free the message Build Completed Successfully will appear in this window Assembling generates a hex file and places it in the same directory as your source code file This is the file that you will download to the PIC microcontroller You can also copy the hex file from the Disk If there are errors in your code then this window will contain the appropriate error messages 3 2 Writing Your Program to the PIC The PIC has a flash type program memory which can be written erased and rewritten This is very useful for debugging you can test out the capabilities and connections of your circuitry before letting your project run amuck Typically the flash memory can go through several thousand of these cycles so you don t need to worry about it breaking down on you Here we are providing two methods to burn a
29. ode is selected the USART automatically attaches start and stop bits to the data We will only be sending byte size data chunks so 8 bit transmit and receive is selected Hardware flow control will be used Now open and configure HyperTerminal with the following settings refer to section 5 0 if necessary 1 9600 Bits Per Second 2 8 Data Bits 3 No Parity 4 1 Stop Bits 5 Hardware Flow Control Load the above program to the PIC and watch the output 5 12 Timer Modules Built into the PIC are three timer modules Timer 0 is a general purpose 8 bit timer counter Timer 1 is a 16 bit timer counter that can be used with the capture compare PWM module Finally timer 2 is an 8 bit timer that is used to control the PWM module Refer to sections 5 7 in the PIC16F87X data sheet for detailed instructions on using the respective timer modules Program which use the Timer Assembly File Hex File Buzzer Example Buzzer asm Buzzer Example Buzzer HEX Pwm Example Pwm asm Pwm Example Pwm HEX Stopwatch Example StopWatch asm Stopwatch Example StopWatch HEX 6 0 How to use the Board Here we have given PIC 16F877A datasheet and Easy Pic Development Board Manual Read the documents carefully As well as we have provided some example files to you Load the hex file to the PIC using the Bootloader software Refer Part III 1 Check the jumper position see Board feature for LCD LED 7Seg amp Key S
30. onnected directly to the PIC but usually a transistor is used A transistor reguires only a small base current to let a much larger current flow through it s collector Also the component that the transistor is switching can have an operating voltage higher than the 5 volts supplying the PIC This makes it an ideal component to control relays from the IO pins of the PIC The relay supplied with this board has an operating voltage of 12 volts Program which use the Relay Assembly File Hex File Relay asm Example Relay asm Relay hex Example Relay HEX 5 9 Buzzer Buzzer is connected in the pin RE2 Normally Buzzer is used to indicate some status to the user This pin can be activated in your programs to audiable indications like pressing of a key confirmation error etc Programs which use the Buzzer Assembly File Hex File Buzzer Example Buzzer asm Buzzer Example Buzzer HEX 5 10 Master Synchronous Serial Port MSSP The Master Synchronous Serial Port MSSP module is used for serial communication with peripheral devices The MSSP module can operate in one of two modes 1 Serial Peripheral Interface SPI 2 Inter Integrated Circuit FC These modes are multiplexed with each other So you can use only one mode at a time Before using MSSP you should remove the I2C or SPI ADC as appropriate see the board 5 10 1 SPI The SPI mode allows 8 bits of data to be svnchronousiv
31. puts movwf TRISA RA2 RAO and RE2 RE1 as outputs 5 1 2 Port B Port B is a general purpose Digital I O Port Data is read from written to port B using the PORTB port register The data direction register This Port is multiplexed with following function e Glow the led in output mode e Getthe input through Key Switches e Control the multiplexed 7Segment LED This Port has following features Support External Interrupt in RBO Support the interrupt on change in RB4 RB7 Table 6 2 Summary of Registers Associated with PORTB m me lu mu us 5 1 3 Port C Port C is shared by many of the peripheral functions such as the timer modules the pulse width modulator the analog to digital converter and the serial communication modules Data is read from written to port C using the PORTC port register The data direction register is TRISC Table 6 3 Summary of Function Associated with PORTC No Port Pins No Functions 1 RCI RC2 Pulse Width Modulation 2 RC0 RC3 RC5 SPI 3 RC3 RC4 RC 4 RC6 RC7 USART Table 6 3 Summary of Registers Associated with PORTC Pra nana Va a rave ser mel 3 1 4 Port D Port D is multiplexed with the Parallel Slave Port PSP module To disable the PSP module the PSPMODE bit TRISE lt 4 gt must be cleared PORTD data direction bits TRISE oxss BE OBP mov Psemope PORTE data direction bits Table 6 4 Summary of Registers Associated w
32. the Segment and Port B is used to select the particular Segment to Glow You have already known the 7Segments are multiplexed with the LCD Before proceeding it you should select 7segment display by changing the jumper to 7Seg position See the Easy Pic Development Board Port B is multiplexed with the keyswitches so changing the jumper to LED position Program which uses the 7Segment LED function Assembly File Hex File 7segment asm Example 7Segment asm 7segment hex Example count HEX Multiplex Example Multiplexing asm Multiplex Example Multiplexing HEX Arith asm Example arith asm Arith hex Example arith HEX Adc asm Example Adc_volt asm Adc hex Example Adc_volt HEX Load the hex file to the PIC and see the output If anything goes wrong check the power socket amp Jumper position 5 4 LCD Device Now you knew this device is multiplexed with 7Segment And you also knew it uses Port D for both control and data lines Before using this device you should change the jumper position to LCD Device See the Board Program which uses the LCD function Assembly File Hex File Leddisplay asm Example LcdDisplay asm Leddisplay hex Example LcdDisplay HEX Acd led c ExampletAde Led c Acd led hex Scanning c Example AdcScan c Scanning hex Example AdcScan HEX Eeprom asm Example EepromLcd asm Eeprom hex Example EepromLed HEX
33. transmitted and received simultaneously All four modes of SPI are supported To accomplish communication typically three pins are used Serial Data Out SDO RC5 SDO Serial Data In SDI RC4 SDI SDA e Serial Clock SCK RC3 SCK SCL LVDIN Additionally a fourth pin may be used when in a Slave mode of operation Slave Select SS RA5 SS AN4 SPI mode uses following register e MSSP Control Register SSPCON e MSSP Status Register SSPSTAT Serial Receive Transmit Buffer SSPBUF e MSSP Shift Register SSPSR Not directly SSPCON and SSPSTAT are the control and status registers in SPI mode operation The SSPCON register is readable and writable The lower 6 bits of the SSPSTAT are read only The upper two bits of the SSPSTAT are read write SSPSR is the shift register used for shifting data in or out SSPBUF is the buffer register to which data bytes are written to or read from In receive operations SSPSR and SSPBUF together create a double buffered receiver When SSPSR receives a complete byte it is transferred to SSPBUF and the SSPIF interrupt is set During transmission the SSPBUF is not double buffered A write to SSPBUF will write to both SSPBUF and SSPSR This board has ADC MCP3202 to explain SPI operation You can connect any other SPI device with the SPI pins Before that you should remove the ADC MCP3202 from the IC socket See the Board Let us see how the SPI device connected with SPI pins External ADC
34. used for data transfer e Serial clock SCL RC3 SCK SCL e Serial data SDA RC4 SDI SDA The user must configure these pins as inputs or outputs through the TRISC lt 4 3 gt bits The MSSP module has six registers for I2C operation These are e MSSP Control Register SSPCON e MSSP Control Register 2 SSPCON2 e MSSP Status Register SSPSTAT e Serial Receive Transmit Buffer SSPBUF e MSSP Shift Register SSPSR Not directly accessible e MSSP Address Register SSPADD Please refer the PIC datasheet for more information It uses only two pins Please remove the SPI device ADC MCP3202 from the board This board has an EEPROM 24LS256 I2C device Also you can connect any number of peripheral that support the I2C communication This EEPROM 24LS256 I2C device is configured as device 1 Programs which use the I2C Function Assembly File Hex File I2C Examplei2c 241c256 HEX I2C Example i2c_241c256 HEX Load the above hex file to the PIC and check the result 5 11 Universal Synchronous Asvnchronous Receiver Transmitter USART The Universal Synchronous Asynchronous Receiver Transmitter USART module is one of the two serial VO modules USART is also known as a Serial Communications Interface or SCI The USART can be configured as a full duplex asynchronous system that can communicate with peripheral devices such as CRT terminals and personal computers or it can be configured as a half dup
35. witch 2 Connect the RS232 cable connector to the Board Port and free com port of computer 3 Connect the power wall adapter 18VDC Barrel Ground 500ma 4 Upload the hex file to the PIC through Bootloader software 5 Check for user file execution by the PIC 6 To view the source code open asm file in Mplab 7 Make correction to asm file if necessary 8 Compile source code with Mplab 9 Repeat steps 4 to 8 as needed
36. wo modes One mode is bootloader mode and another one is Programmer mode It then steps through the features of the PIC microcontroller one by one complete with instructions diagrams sample code and working examples Eguipped with the information provided here you will be able to unleash the full capabilities of the Easy Pic Development Board V Appendices These are referenced by the three previous parts Feel free to detach the appendices from the bulk of this manual you will likely refer to them often This manual is intended to be a supplement to the PIC16F877A data sheet The PIC16F877A data sheet includes absolutely everything you will need to know about the PIC16F87X microcontroller and this user manual refers to it often Another helpful reference is the PICmicro Midrange Reference Manual I would sincerely recommend taking the time to read this entire manual from beginning to end and to familiarize yourself with the data sheet the things you will learn along the way will be helpful when it comes to designing your own project Be aware however that completion of this manual will merely lay the groundwork for more interesting albeit more useful applications of the Easy Pic Development Board Keep in mind that the Easy Pic Development Board is just the central nervous system of your project You are responsible for the design of the extraneous circuits that your project will utilize sensors motors etc It would be prudent to mak
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