;************************************************************************************ ; Software License Agreement ; ; The software supplied herewith by Microchip Technology Incorporated (the "Company") ; for its PICmicro(r) Microcontroller is intended and supplied to you, the Company's ; customer, for use solely and exclusively on Microchip PICmicro Microcontroller ; products. ; ; The software is owned by the Company and/or its supplier, and is protected under ; applicable copyright laws. All rights are reserved. Any use in violation of the ; foregoing restrictions may subject the user to criminal sanctions under applicable ; laws, as well as to civil liability for the breach of the terms and conditions of ; this license. ; ; THIS SOFTWARE IS PROVIDED IN AN "AS IS" CONDITION. NO WARRANTIES, WHETHER EXPRESS, ; IMPLIED OR STATUTORY, INCLUDING, BUT NOT LIMITED TO, IMPLIED WARRANTIES OF ; MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE APPLY TO THIS SOFTWARE. THE ; COMPANY SHALL NOT, IN ANY CIRCUMSTANCES, BE LIABLE FOR SPECIAL, INCIDENTAL OR ; CONSEQUENTIAL DAMAGES, FOR ANY REASON WHATSOEVER. ; ;************************************************************************************ ; ; Filename: BackEMF.asm ; Date: April 18, 2005 ; File Version: 1.00 ; ; Company: Microchip Technology Inc. ; ;************************************************************************************ ; ; Files required: ; BackEM.inc ; LCD.inc ; 16f917.lkr ; LCD.asm ; ;************************************************************************************ ; ; Notes: This project measures the Back Electromagnetic Flux (EMF) produced by ; a brushed DC motor. The windings of a brushed dc motor (or any number of ; other motors) will produce a voltage when the motor is spinning that is ; proportional to the speed of the motor. Therefor if a motor is being ; driven, and the drive voltage is temporarily removed from the motor, the ; voltage across the windings can be measured and the approximate speed of ; the motor deduced. ; ; Connections: ; POT1 (J4) to RA0 (J13) ; BACK EMF (J16) to RA4 (J13) ; P1 (J1) to RD7 (J10) ; N2 (J1) to CCP2 (J10) ; ;************************************************************************************ #include ;********************************************************************** STARTUP code goto Initialize PORT1 code ;************************************************************************************ ; Initialize - Initialize CCP1, comparators, internal oscillator, I/O pins, ; analog pins, motor parameters, variables ; ;************************************************************************************ Initialize clrf STATUS ; bank 0 bsf STATUS,RP0 ; we'll set up the bank 1 Special Function Registers fist ; Configure I/O pins for project bsf TRISA,0 ; RA0 is an input bsf TRISA,4 ; RA4 is an input bsf TRISA,5 ; RA5 is an input bcf TRISD,7 ; RD7 is an output bcf TRISD,2 ; RD2 is an output ; Set internal oscillator frequency movlw b'01110000' ; 8Mhz movwf OSCCON ; Set up A-to-D Module movlw b'00010001' ; enable AN0 and AN4 movwf ANSEL movlw b'01100000' ; Fosc/16 movwf ADCON1 ; Configure PR2 to movlw 0x3F ; 31.2 kHz PWM movwf PR2 ; Set TMR0 parameters MOVLW B'10000111' ;PORTB PULL-UP DISABLED MOVWF OPTION_REG ;TMR0 RATE 1:256 ; Turn off comparators movlw 0x07 movwf CMCON0 ; turn off comparators bcf STATUS,RP0 ; go back to bank 0 ; Finish setting up A-to-D Module movlw b'00010001' ; left justified, AN4 selected, module on movwf ADCON0 ; Configure Capture Compare PWM Module clrf CCPR2L movlw b'00001100' ; pwm mode movwf CCP2CON bsf T2CON,TMR2ON ; turn on PWM clrf PORTD ; Turn off Motor ;************************************************************************************ ; Main - Sets the speed of the motor based on the position of POT1. ; The Back EMF is measured, converted to RPM, and then displayed. ; ;************************************************************************************ Main call InitLCD ; Initialize LCD Special Function Registers bsf P1 ; Turn on P-Channel MOSFET clrf Pointer clrf TimeKeeper Loop btfss INTCON,T0IF ; Every 32.768ms exit this loop and do something goto Loop bcf INTCON,T0IF incf TimeKeeper,f ; This keeps track of the number of time intervals gone by call ReadBackEMF ; Read the Back EMF call SetMotorSpeed ; Set the speed of the motor based on the position of POT1 btfss TimeKeeper,5 ; Every 1.048 seconds display the RPM (Displayed value = RPM x 10^3) goto EndLoop call DisplayRPM clrf TimeKeeper EndLoop goto Loop ;************************************************************************************ ; ReadBackEMF - Read the Back EMF, store the value in a 64-byte circular buffer, ; calculate the average of the values in the buffer, and convert this average to ; RPM. ; ;************************************************************************************ ReadBackEMF ; Read Back EMF and store bcf P1 ; Turn off P-Channel MOSFET movlw 0xF0 andwf CCP2CON,f ; Turn off PWM nop bsf N2 ; Turn on N-Channel MOSFET movlw 0x50 movwf Counter Delay ; Delay for approx 120us (0x50 * 3 instructions * 4/Fosc) decfsz Counter,f goto Delay movlw 0x3F andwf Pointer,w ; pointer is a rolling pointer from 0 to 63 addlw BackEMFValue movwf FSR ; point to next storage byte clrf STATUS ; IRP bit needs to be clear bsf ADCON0,GO_DONE ; Start A-to-D conversion ReadBEMFLoop btfsc ADCON0,GO_DONE ; Wait for conversion to complete goto ReadBEMFLoop movf ADRESH,w ; Store Back EMF value in buffer movwf INDF incf Pointer,f movlw b'00000001' ; aquire AN0 in preparation for POT1 read movwf ADCON0 TurnOnMotor movlw 0x0F ; Turn on PWM iorwf CCP2CON,f bsf P1 ; Turn on P-Channel MOSFET call AverageBEMF ; Find the average Back EMF Value and Convert to RPM return ;************************************************************************************ ; SetMotorSpeed - Read the analog voltage output by the potentiometer. Move this ; 8-bit value into the duty cycle registers of the CCP2 module. This module is ; running with a duty cycle resolution of 8-bits in order to produce a frequency of ; 31.2kHz. This frequency is sufficient high to prevent the motor for making an ; annoying whine at low speeds. (31.2kHz is outside the audible range of the human ; ear.) ; ;************************************************************************************ SetMotorSpeed bsf ADCON0,GO_DONE ReadPOT1Loop btfsc ADCON0,GO_DONE goto ReadPOT1Loop movf ADRESH,w ; store POT1 ADC value movwf DutyCycle movlw b'00010001' ; aquire AN4 in preparation for Back EMF read movwf ADCON0 swapf DutyCycle,w ; bits 4 and 5 of CCP2CON andlw 0x30 iorlw 0x8D movwf CCP2CON rrf DutyCycle,f ; move most significant 6 bits of duty cycle into rrf DutyCycle,w ; CCPR2L andlw 0x3F movwf CCPR2L return ;************************************************************************************ ; DisplayRPM - Convert RPM to binary coded decimal and display the 3 most significant ; bits (thousands, hundreds, and tens. ; ; Example: RPM = 4520 ; Display will show 4.52 K (K indicates the display number should be multiplied by ; 1000) ; ;************************************************************************************ DisplayRPM movf RPM_High,w movwf H_byte movf RPM_Low,w movwf L_byte call ConvertToBCD ; This function is taken from AN526. Why write code that is already written? swapf R2,w ; This is the Tens digit andlw 0x0F call DisplayDigit1 movf R1,w ; This is the Hundreds digit andlw 0x0F call DisplayDigit2 swapf R1,w ; This is the Thousands digit andlw 0x0F call DisplayDigit3 call Display3DP ; Put the decimal point between the hundreds and thousands digits call DisplayK ; Display K to indicate RPM = (value on LCD) * 1000 return ;************************************************************************************ ; AverageBEMF - Adds all 64 BackEMF values that are stored. This number is divided ; by 64. This gives the average Back EMF value. This number is then muliplied by ; 26. (In actuality, the divide by 64 and multiply by 26 are done simultaneously) ; ;************************************************************************************ AverageBEMF clrf STATUS clrf Math_Low clrf Math_High movlw BackEMFValue movwf FSR movlw .64 movwf Counter AddLoop ; Add up all 64 Back EMF measurements stored in the circular buffer movf INDF,w addwf Math_Low,f btfsc STATUS,C incf Math_High,f incf FSR,f decfsz Counter,f goto AddLoop ConvertToRPM ; We have to divide by 64 and then multiple by 26. Why not do it simultaneously? AverageAndMultiply ; Divide by 64 while multiplying by 26 (26 = 16+8+2) bcf STATUS,C rrf Math_High,f ; /4 (multiply by 16) rrf Math_Low,f rrf Math_High,f rrf Math_Low,f movf Math_Low,w andlw b'11110000' movwf RPM_Low movf Math_High,w andlw b'00001111' movwf RPM_High bcf STATUS,C rrf Math_High,f ; /8 (add multiply by 8) rrf Math_Low,f movf Math_Low,w andlw b'11111000' addwf RPM_Low,f btfsc STATUS,C incf RPM_High,f movf Math_High,w andlw b'00000111' addwf RPM_High,f bcf STATUS,C rrf Math_High,f ; /32 (add multiply by 2) rrf Math_Low,f rrf Math_High,f rrf Math_Low,f movf Math_Low,w andlw b'11111110' addwf RPM_Low,f btfsc STATUS,C incf RPM_High,f movf Math_High,w andlw b'00000001' addwf RPM_High,f return ;************************* Taken from AN526 ********************************** ; Binary To BCD Conversion Routine ; This routine converts a 16 Bit binary Number to a 5 Digit ; BCD Number. This routine is useful since PIC16C55 & PIC16C57 ; have two 8 bit ports and one 4 bit port ( total of 5 BCD digits) ; ; The 16 bit binary number is input in locations H_byte and ; L_byte with the high byte in H_byte. ; The 5 digit BCD number is returned in R0, R1 and R2 with R0 ; containing the MSD in its right most nibble. ; ; Performance : ; Program Memory : 35 ; Clock Cycles : 885 ; ; ; Program: B16TOBCD.ASM ; Revision Date: ; 1-13-97 Compatibility with MPASMWIN 1.40 ; ;*******************************************************************; ConvertToBCD bcf STATUS,0 ; clear the carry bit movlw .16 movwf count clrf R0 clrf R1 clrf R2 loop16 rlf L_byte, F rlf H_byte, F rlf R2, F rlf R1, F rlf R0, F ; decfsz count, F goto adjDEC RETLW 0 ; adjDEC movlw R2 movwf FSR call adjBCD ; movlw R1 movwf FSR call adjBCD ; movlw R0 movwf FSR call adjBCD ; goto loop16 ; adjBCD movlw 3 addwf 0,W movwf temp btfsc temp,3 ; test if result > 7 movwf 0 movlw 30 addwf 0,W movwf temp btfsc temp,7 ; test if result > 7 movwf 0 ; save as MSD RETLW 0 END ; directive 'end of program'