TITLE "Frequency Counter" List P=PIC16F648a, R=DEC INCLUDE "p16f648a.inc" SCL EQU 2 ; Clock line setup SDA EQU 3 ; Data line setup BLANK EQU 11 ESYM EQU 10 ; data segment in BANK 0 CBLOCK 0x20 d, cnt, del:2, FSR_save ; local variables w_save, stat_save, pc_save ; ISR variables dataIO ; I2C interface variable digits:4, digits2:4 ; storage for digits to display on LCD freq:4 ; storage for the (binary) frequency value freqLen ; number of decimal digits in freq tmillions:3, millions:2 ; constants needed for the BCD conversion hthousands:2, tthousands:2 thousands:2 first, order, point, mode ; freq aux. parameters ENDC ; code segment PAGE __CONFIG _CP_OFF & _DATA_CP_OFF & _LVP_OFF & _BOREN_OFF & _MCLRE_OFF & _PWRTE_ON & _WDT_OFF & _XT_OSC ORG 0 goto main ORG 4 ; ISR (execusion time 18*40 = 720usec) movwf w_save ; save Wreg swapf STATUS, w ; save stat reg without movwf stat_save ; changing flags btfss PIR1, TMR1IF ; is it TMR1 interrupt? goto ISR_end ; NO - back to the main code incf freq+3, f ; increment the TMR1 overflow counter bcf PIR1, TMR1IF ; clear TMR1 interrupt flag ISR_end swapf stat_save, w ; get original flags in STATUS movwf STATUS swapf w_save, f ; restore Wreg swapf w_save, w retfie encode7seg ; setup for 7-seg digit codes andlw 0x0F addwf PCL, f ; bit 5 is the decimal point retlw b'11001111' ; digit 0 retlw b'11000000' ; digit 1 retlw b'01011110' ; digit 2 retlw b'11011100' ; digit 3 retlw b'11010001' ; digit 4 retlw b'10011101' ; digit 5 retlw b'10011111' ; digit 6 retlw b'11001000' ; digit 7 retlw b'11011111' ; digit 8 retlw b'11011101' ; digit 9 retlw b'00011111' ; letter E retlw b'00000000' ; blank retlw b'00000000' ; blank retlw b'00000000' ; blank retlw b'00000000' ; blank retlw b'00000000' ; blank getPointIndex ; needed for displaying the decimal point addwf PCL, f retlw 3 ; for mode=0 retlw 2 retlw 1 retlw 3 retlw 2 retlw 1 retlw -1 retlw -1 retlw -1 ; for mode=1 retlw -1 retlw 3 retlw 2 retlw 1 retlw -1 retlw -1 retlw -1 getOrder ; display frequency exponent addwf PCL, f ; E6 = MHz retlw 6 ; E3 = KHz retlw 6 ; E0 = Hz retlw 6 retlw 3 retlw 3 retlw 0 retlw 0 retlw 0 main ; main code bcf STATUS, RP0 ; activate BANK 0 clrf PORTA ; initialize PORT A clrf PORTB ; initialize PORT B movlw 0x07 movwf CMCON ; comparators OFF bsf STATUS, RP0 ; change to BANK 1 movlw b'00101100' movwf TRISA ^ 0x80 ; enable RA5 and RA<3:2> for input movlw b'11110011' movwf TRISB ^ 0x80 ; enable output on RB<3:2> movlw 249 movwf PR2 ^ 0x80 ; TMR2 period (250*4*16*0.01=160msec) bsf PIE1 ^ 0x80, TMR1IE ; enable TMR1 interrupts bcf STATUS, RP0 ; back to BANK 0 movlw 156 movwf CCPR1L ; PWM duty cycle (100msec) movlw b'00011100' movwf CCP1CON ; switch to PWM mode movlw 3 movwf T2CON ; TMR2 1:16 prescaler movlw 6 movwf T1CON ; setup TMR1 (external clock, no synch) clrf TMR1L ; clear the TMR1 counter clrf TMR1H clrf freq+3 ; clear the TMR1 overflow counter clrf mode ; mode=0 if T=0.1sec and mode=1 if T=1sec bsf INTCON, PEIE ; enable periferal interrupts bsf INTCON, GIE ; enable interrupts system call delay1ms ; required for PCF8562 call initialize ; setup PCF8562 bsf PORTB, 2 ; enable 74LV161A counter bsf T2CON, TMR2ON ; start PWM and also Freq count mode bsf T1CON, TMR1ON nop ; short delay ; call testLCD ; goto $ loop btfsc PORTB, 1 ; end of freq measurement cycle? goto $-1 ; Not yet - wait bcf T1CON, TMR1ON ; disable TMR1 for counting call getFreq ; read the freq value from TMR1 and 74LV161A bcf PORTB, 2 ; clear 74LV161A and disable it for counting call freq2BCD ; convert freq into BCD representation movf freqLen, w addwf freq, f ; now freq = 1 iff originally freq = 0 movlw 5 ; default freq counting interval is 0.1sec subwf freqLen, w ; if freq value is less than 5 decimal digits decf freq, f ; (here Z=1 iff originally freq=0) movlw 5 ; we measure the freq again in a 1sec interval andwf STATUS, w ; and set mode=1 btfsc STATUS, Z ; here we check if both Z and C bits are 0 call countLowFreq ; count freq in 1 sec interval call displayFreq ; display freq on LCD clrf TMR1L ; clear the freq counters clrf TMR1H ; for the next cycle clrf freq+3 clrf mode ; back to default mode=0 and 0.1sec counting btfss PORTB, 1 ; wait for a PWM pulse goto $-1 ; (probably not needed) btfsc PORTB, 1 ; wait for the end of pulse goto $-1 bsf PORTB, 2 ; enable 74LV161A for counting bsf T1CON, TMR1ON ; enable TMR1 for counting btfss PORTB, 1 ; wait for a PWM pulse again goto $-1 goto loop ; procedures countLowFreq incf mode, f ; set mode=1 movlw 52 ; settings for a 1sec delay movwf del movlw 13 movwf del+1 movlw 0xF0 andwf CCP1CON, f ; disable PWM at RB3 bcf INTCON, GIE ; disable interrupts clrf TMR1L ; clear the TMR1 counter clrf TMR1H bsf T1CON, TMR1ON ; enable TMR1 for counting bsf PORTB, 2 ; stop clearing 74LV161A bsf PORTB, 3 ; enable 74LV161A for counting movlw 1 ; this fragment takes 25000 instruction subwf del, f ; cycles and provides a 1 sec delay btfss STATUS, C ; by running PIC at 100KHz decf del+1, f movf del+1, w ; during this time interval the freq btfss STATUS, Z ; count is taken by 74LV161A and TMR1; goto $-6 ; TMR1 does not overflow, so freq+3 = 0 nop ; end of a 1sec delay bcf PORTB, 3 ; disable 74LV161A for counting bcf T1CON, TMR1ON ; disable TMR1 for counting call getFreq ; read the freq value from TMR1 and 74LV161A clrf freq+3 bcf PIR1, TMR1IF ; clear TMR1 interrupt flag bsf INTCON, GIE ; enable interrupts bcf PORTB, 2 ; clear 74LV161A and disable it for counting movlw 0x0F iorwf CCP1CON, f ; enable PWM at RB3 call freq2BCD ; convert freq into BCD representation return getFreq movf PORTB, w ; get 74LV161A counted value movwf freq rlf freq, f bcf freq, 4 btfsc STATUS, C bsf freq, 4 movlw 0xF0 ; clear the lower nibble andwf freq, f movf TMR1L, w ; get the TMR1 value in freq+2:freq+1 movwf freq+1 ; freq+3 is set by the ISR movf TMR1H, w movwf freq+2 ; at this point the freq counter is set up return ; code from here to freq2BCD is under development btfss freq, 7 ; software correction of the TMR1 value: return ; it is only needed if not all bits movlw b'11110000' ; of freq are set subwf freq, w ; in this case TMR1 has counted an extra pulse btfsc STATUS, Z ; so we need to subtract 1 from return ; (freq+3):(freq+1) to compensate this correction movlw 1 ; decrementing a 3-byte value subwf freq+1, f clrw clrf d btfss STATUS, C incfsz d, w subwf freq+2, f clrw btfss STATUS, C addlw 1 subwf freq+3, f ; end of software correction btfss freq+3, 7 ; the above correction was only needed return ; if freq+3:freq+2:freq+1 is non-zero clrf freq+1 ; in which case no correction is needed clrf freq+2 ; we fix it by clearing the values of clrf freq+3 ; freq+3:freq+2:freq+1 return freq2BCD clrf freqLen ; number of decimal digits in freq call getFirstDigit call getSecondDigit call getThirdDigit call getFourthDigit bcf STATUS, C ; shift freq 4 bits to the right rrf freq+2, f ; at this point freq is at most 16-bit rrf freq+1, f rrf freq, f rrf freq+2, f rrf freq+1, f rrf freq, f rrf freq+2, f rrf freq+1, f rrf freq, f rrf freq+2, f rrf freq+1, f rrf freq, f call getFifthDigit call getSixthDigit call getLastDigits movlw 8 subwf freqLen, w sublw 0 movwf first ; index of freq's first digit movlw 6 ; no rounding off is needed subwf freqLen, w ; C=0 if freqLen < 6 btfss STATUS, C goto normalize roundoff movlw digits movwf FSR movf first, w addlw 5 ; index of the rounding off digit addwf FSR, f movf INDF, w ; w = rounding off digit sublw 4 ; C=0 if digit >=5 btfsc STATUS, C goto normalize decf FSR, f ; get to the 5-th freq digit incf INDF, f ; round it off movlw 10 subwf INDF, w ; is it 10 after rounding off? btfss STATUS, Z goto normalize ; NO - proceed clrf INDF ; YES - clear the digit decf FSR, f ; and round off the previous one incf INDF, f ; round off the 4-th digit movlw 10 subwf INDF, w ; is it 10 after rounding off? btfss STATUS, Z goto normalize ; NO - proceed clrf INDF ; YES - clear the digit decf FSR, f ; and round off the previous one incf INDF, f ; round off the 3-rd digit movlw 10 subwf INDF, w ; is it 10 after rounding off? btfss STATUS, Z goto normalize ; NO - proceed clrf INDF ; YES - clear the digit decf FSR, f ; and round off the previous one incf INDF, f ; round off the 2-nd digit movlw 10 subwf INDF, w ; is it 10 after rounding off? btfss STATUS, Z goto normalize ; NO - proceed clrf INDF ; YES - clear the digit decf FSR, f ; and round off the previous one incf INDF, f ; round off the 1-st movlw 10 subwf INDF, w ; is it 10 after rounding off? btfss STATUS, Z goto normalize ; NO - proceed clrf INDF ; YES - clear the digit decf FSR, f ; and round off the previous one incf INDF, f ; the previous digit=0; this happens decf first,f ; only for freq=999999, so the prev. exists normalize movf first, w ; compute the order call getOrder movwf order movf mode, w ; compute position of the decimal point btfss STATUS, Z movlw 8 ; w = mode*8 addwf first, w call getPointIndex ; get position from the table movwf point return displayFreq movlw 5 ; freqLen = max(freqLen, 5) subwf freqLen, w movlw 5 btfsc STATUS, C movwf freqLen call start_I2C movlw b'01110000' ; slave address movwf dataIO call write_I2C clrf dataIO ; clear the address pointer call write_I2C movf order, w ; sending the order call encode7seg movwf dataIO call write_I2C movlw ESYM ; sending the E symbol call encode7seg movwf dataIO call write_I2C movlw BLANK ; separating space character call encode7seg movwf dataIO call write_I2C movf freqLen, w ; sending freqLen digits to the LCD movwf d movlw digits addwf first, w addwf freqLen, w addlw -1 movwf FSR_save ; FSR points to the last digit digitsLoop movf FSR_save, w ; restore the FSR movwf FSR ; index of the first digit movf INDF, w ; get digit call encode7seg movwf dataIO movf d, w ; check if the decimal point subwf point, w ; should be displayed btfsc STATUS, Z bsf dataIO, 5 ; ... and turn it on, if needed decf FSR, w ; update the digits pointer movwf FSR_save ; and save it movlw 0x85 ; load FSR with the address of TRISB movwf FSR call write_I2C decfsz d, f goto digitsLoop movf freqLen, w sublw 4 ; w = 4 - freqLen btfss STATUS, C ; C=1 if freqLen < 5 goto $+9 addlw 1 movwf d ; add d spaces movlw BLANK ; send the blanks to the LCD call encode7seg movwf dataIO call write_I2C decfsz d, f goto $-5 call stop_I2C return getFirstDigit clrf digits movf tmillions, w ; 24-bit subtract subwf freq+1, f movf tmillions+1, w btfss STATUS, C incfsz tmillions+1, w subwf freq+2, f movf tmillions+2, w btfss STATUS, C incfsz tmillions+2, w subwf freq+3, f ; subtraction is completed incf digits, f ; update the counter btfsc STATUS, C goto getFirstDigit+1 decf digits, f ; restore the counter btfss STATUS, Z incf freqLen, 1 ; update the number of decimal digits movf tmillions, w ; restore freq (add 10^7 to it) addwf freq+1, f movf tmillions+1, w btfsc STATUS, C incfsz tmillions+1, w addwf freq+2, f movf tmillions+2, w btfsc STATUS, C addlw 1 ; here the correct C bit is not needed addwf freq+3, f return getSecondDigit clrf digits+1 movf millions, w ; get the first byte subwf freq+1, f ; movf millions+1, w btfss STATUS, C incfsz millions+1, w subwf freq+2, f clrw clrf d ; the 3d byte of millions is 0 btfss STATUS, C incfsz d, w subwf freq+3, f ; subtraction is completed incf digits+1, f ; update the counter btfsc STATUS, C goto getSecondDigit+1 decf digits+1, f ; restore the counter movf digits+1, w ; update the freq length addwf freqLen, w btfss STATUS, Z incf freqLen, f movf millions, w ; restore freq (add 10^6 to it) addwf freq+1, f movf millions+1, w btfsc STATUS, C incfsz millions+1, w addwf freq+2, f clrw btfsc STATUS, C addlw 1 ; here the correct C bit is not needed addwf freq+3, f return getThirdDigit clrf digits+2 movf hthousands, w ; get the first byte subwf freq+1, f movf hthousands+1, w btfss STATUS, C incfsz hthousands+1, w subwf freq+2, f ; subtraction is completed incf digits+2, f ; update the counter btfsc STATUS, C goto getThirdDigit+1 decf digits+2, f ; restore the counter movf digits+2, w ; update the freq length addwf freqLen, w btfss STATUS, Z incf freqLen, f movf hthousands, w ; restore freq (add 10^5 to it) addwf freq+1, f movf hthousands+1, w btfsc STATUS, C addlw 1 addwf freq+2, f return getFourthDigit clrf digits+3 movf tthousands, w ; get the first byte subwf freq+1, f movf tthousands+1, w btfss STATUS, C incfsz tthousands+1, w subwf freq+2, f ; subtraction is completed incf digits+3, f ; update the counter btfsc STATUS, C goto getFourthDigit+1 decf digits+3, f ; restore the counter movf digits+3, w ; update the freq length addwf freqLen, w btfss STATUS, Z incf freqLen, f movf tthousands, w ; restore freq (add 10^4 to it) addwf freq+1, f movf tthousands+1, w btfsc STATUS, C addlw 1 addwf freq+2, f return getFifthDigit clrf digits+4 ; at this point freq is 16-bit movf thousands, w ; get the first byte subwf freq, f movf thousands+1, w btfss STATUS, C incfsz thousands+1, w subwf freq+1, f ; subtraction is completed incf digits+4, f ; update the counter btfsc STATUS, C goto getFifthDigit+1 decf digits+4, f ; restore the counter movf digits+4, w ; update the freq length addwf freqLen, w btfss STATUS, Z incf freqLen, f movf thousands, w ; restore freq (add 10^3 to it) addwf freq, f movf thousands+1, w btfsc STATUS, C addlw 1 addwf freq+1, f return getSixthDigit clrf digits+5 ; at this point freq is 16-bit movlw 100 subwf freq, f clrw clrf d btfss STATUS, C incfsz d, w subwf freq+1, f ; subtraction is completed incf digits+5, f ; update the counter btfsc STATUS, C goto getSixthDigit+1 decf digits+5, f ; restore the counter movf digits+5, w ; update the freq length addwf freqLen, w btfss STATUS, Z incf freqLen, f movlw 100 ; restore freq (add 100 to it) addwf freq, f clrw btfsc STATUS, C addlw 1 addwf freq+1, f return getLastDigits clrf digits+6 ; at this point freq is 8-bit movlw 10 ; get the first byte subwf freq, f ; C=0 if diff<0 incf digits+6, f ; update the counter btfsc STATUS, C goto getLastDigits+1 decf digits+6, f ; restore the counter movf digits+6, w ; update the freq length addwf freqLen, w btfss STATUS, Z incf freqLen, f movlw 10 ; restore freq (add 10 to it) addwf freq, w movwf freq movwf digits+7 ; set the last digit incf freqLen, f ; update freq length return testLCD clrf digits movlw 1 movwf digits+1 movlw 2 movwf digits+2 movlw 3 movwf digits+3 movlw 4 movwf digits+4 movlw 5 movwf digits+5 movlw 6 movwf digits+6 movlw 7 movwf digits+7 clrf d call start_I2C movlw b'01110000' ; slave address movwf dataIO call write_I2C clrf dataIO ; reset the address pointer call write_I2C movf digits, w call encode7seg movwf dataIO call write_I2C movf digits+1, w call encode7seg movwf dataIO call write_I2C movf digits+2, w call encode7seg movwf dataIO call write_I2C movf digits+3, w call encode7seg movwf dataIO call write_I2C movf digits+4, w call encode7seg movwf dataIO call write_I2C movf digits+5, w call encode7seg movwf dataIO call write_I2C movf digits+6, w call encode7seg movwf dataIO call write_I2C movf digits+7, w call encode7seg movwf dataIO call write_I2C call stop_I2C return initialize call start_I2C ; PCF8562 initialization movlw b'01110000' ; slave address movwf dataIO call write_I2C movlw b'11001011' ; 1:3 drive mode w. 1/3 bias movwf dataIO call write_I2C clrf dataIO ; reset the address pointer call write_I2C clrw call encode7seg ; display 0 movwf dataIO call write_I2C call stop_I2C ; end of initialization movlw b'01101000' ; constants used for BCD conversion movwf tmillions movlw b'10001001' movwf tmillions+1 movlw 9 movwf tmillions+2 movlw b'00100100' movwf millions movlw b'11110100' movwf millions+1 movlw b'01101010' movwf hthousands movlw b'00011000' movwf hthousands+1 movlw b'01110001' movwf tthousands movlw 2 movwf tthousands+1 movlw b'11101000' movwf thousands movlw 3 movwf thousands+1 return start_I2C ; start setup for I2C interface movlw 0x85 ; setup FSR to point to TRISA movwf FSR movlw b'11110011' andwf PORTA, f bsf INDF, SDA ; pull high SDA and SCL bsf INDF, SCL goto $+1 ; delay slot bcf INDF, SDA ; set data low nop ; wait for slave to detect it bcf INDF, SCL ; set clock low return stop_I2C ; stop setup for I2C interface movlw b'11110011' andwf PORTA, f bcf INDF, SCL ; make sure that clock and data bcf INDF, SDA ; lines are low goto $+1 bsf INDF, SCL ; release clock line goto $+1 bsf INDF, SDA ; release data line return write_I2C ; write byte to I2C line movlw b'11110011' andwf PORTA, f bcf INDF, SCL ; make sure that clock is low movlw 8 movwf cnt ; bits counter w_loop bcf INDF, SDA ; start w. data bit low rlf dataIO, f ; get the rightmost data bit btfsc STATUS, C bsf INDF, SDA ; now the data bit is on the data bus bsf INDF, SCL ; raise clock up bcf INDF, SCL ; ... and low decfsz cnt, f goto w_loop ; repeat this 8 times bsf INDF, SDA ; get ACK from slave nop ; let slave respond bsf INDF, SCL ; clock up nop ; slave responds OK (hopefully) bcf INDF, SCL ; clock down return delay1ms movlw 5 sublw 1 ; this loop takes 200us*5 = 1ms sublw 0 ; for PIC16F648a @ 100 kHz btfss STATUS, Z goto $-3 return setTestFreq movlw b'10110000' movwf freq movlw b'00000000' movwf freq+1 movlw b'00000000' movwf freq+2 movlw b'00000000' movwf freq+3 return end