LIST P=12F683, R=DEC INCLUDE "p12F683.inc" __CONFIG _BOD_OFF & _CPD_OFF & _CP_OFF & _MCLRE_OFF & _PWRTE_ON & _WDT_OFF & _INTOSCIO #define RXout GPIO,4 ; RX output pin tZone EQU -6 ; setup for CST time zone SCL EQU 2 ; Clock line setup SDA EQU 5 ; Data line setup zeroL EQU 150 * 1000/16 ; zero threshold for PIC @ 4 MHz zeroH EQU zeroL + 100*1000/16 oneL EQU 450 * 1000/16 ; one threshold oneH EQU oneL + 100*1000/16 synL EQU 750 * 1000/16 ; sync threshold synH EQU synL + 100*1000/16 CBLOCK 0x20 ; data segment w_save, stat_save ; storage for saving CPU state length:2 ; storage for pulse width pulse ; storage for received pulse value temp:2 ; temp variable del ; delay variable state ; receiver FSM state seconds, minutes, hours:2 ; storade for the time/datae data days:2, year:2, day, month pulseNo, wwvbByte ; pulse number and byte received dataIO, cnt ; LCD interface ENDC ORG 0 ; code segment goto main ORG 4 ; ISR movwf w_save ; save Wreg swapf STATUS, w ; save stat reg without movwf stat_save ; changing flags btfsc RXout goto pulseEnd ; YES - process end of pulse pulseStart btfsc pulse, 0 ; display previously received pulse bsf GPIO, 0 btfsc pulse, 1 bsf GPIO, 1 call delay100msec bcf GPIO, 0 bcf GPIO, 1 movlw 7 ; increment seconds in BCD addwf seconds, w btfss STATUS, DC addlw -6 movwf seconds movlw 6*16 subwf seconds, w btfsc STATUS, Z ; seconds = 60 ? clrf seconds ; YES - clear seconds process ; call processPulse ; call updateLCD goto ISR_end+1 pulseEnd bcf T1CON, 0 ; disable timer movf TMR1L, w ; save pulse duration movwf length movf TMR1H, w movwf length+1 clrf TMR1L ; clear timer clrf TMR1H movlw 4 movwf pulse btfsc PIR1, TMR1IF ; was there timer overlow? goto ISR_end ; YES - exit movlw LOW zeroL ; check for received 0 subwf length, w movlw HIGH zeroL movwf temp btfss STATUS, C incfsz temp, w subwf length+1, w btfss STATUS, C goto srt ; too short pulse - ignore it movlw LOW zeroH ; check for received 0 subwf length, w movlw HIGH zeroH movwf temp btfss STATUS, C incfsz temp, w subwf length+1, w btfss STATUS, C goto r0 ; accept pulse as 0 movlw LOW oneL ; check for received 1 subwf length, w movlw HIGH oneL movwf temp btfss STATUS, C incfsz temp, w subwf length+1, w btfss STATUS, C goto srt ; too short for 1 - ignore movlw LOW oneH ; check for received 1 subwf length, w movlw HIGH oneH movwf temp btfss STATUS, C incfsz temp, w subwf length+1, w btfss STATUS, C goto r1 ; accept pulse as 1 movlw LOW synL ; check for received sync subwf length, w movlw HIGH synL movwf temp btfss STATUS, C incfsz temp, w subwf length+1, w btfss STATUS, C goto srt ; too short for sync - ignore movlw LOW synH ; check for received sync subwf length, w movlw HIGH synH movwf temp btfss STATUS, C incfsz temp, w subwf length+1, w btfss STATUS, C goto rS ; accept pulse as sync ; goto ISR_end srt decf pulse, f ; out of range duration: pulse=0 r0 decf pulse, f ; received 0: pulse=1 r1 decf pulse, f ; received 1: pulse=2 rS decf pulse, f ; sync signal: pulse=3 call processPulse call updateLCD ISR_end bsf T1CON, 0 ; enable timer bcf INTCON, GPIF ; clear interrupt flag bcf PIR1, TMR1IF ; clear TMR1 interrupt flag swapf stat_save, w ; get original flags in STATUS movwf STATUS swapf w_save, f ; restore Wreg swapf w_save, w retfie main bcf STATUS, RP0 ; switch to BANK 0 movlw b'011000' movwf GPIO ; initialize GPIO movlw 7 movwf CMCON0 ; disable the comparator clrf ADCON0 ; ADC OFF bsf STATUS, RP0 ; change to BANK 1 clrf ANSEL ^ 0x80 ; all inputs digital movlw b'111100' movwf TRISIO ^ 0x80 ; enable GPIO<4:3> for input bsf IOC ^ 0x80, 4 ; enable interrupt on change at GPIO:4 movlw b'01010000' movwf OSCCON ^ 0x80 ; set clock freq = 2MHz bcf STATUS, RP0 ; back to BANK 0 movlw b'01110100' ; setup timer TMR1 with 1:8 prescaler movwf T1CON bsf INTCON, GPIE ; enable interrupts on GPIO change call delay100msec call delay100msec clrf hours clrf minutes clrf seconds clrf days clrf days+1 clrf year clrf year+1 clrf pulse clrf month clrf day ; movlw 0x15 ; movwf hours ; goto correctHours ; movlw 0x33 ; movwf days+1 ; movlw 0x20 ; goto computeDate btfss RXout ; wait for the pulse absence goto $-1 clrf state clrf TMR1L ; clear timer clrf TMR1H bcf INTCON, GPIF ; clear interrupt flag bcf PIR1, TMR1IF ; clear TMR1 interrupt flag bsf T1CON, 0 ; enable timer bsf INTCON, GIE ; enable interrupts globally loop ; sleep nop goto loop ;#################### procedures processPulse movf pulse, w ; check pulse duraction for being legal btfss STATUS, Z goto accept clrf state ; illegal duration - return to state 0 return accept movf state, w andlw 0x03 addwf PCL, f goto sync1 goto sync2 goto getByte sync1 ; state 0: waiting for the first sync pulse clrf seconds movlw 3 subwf pulse, w ; Z=0: sync btfsc STATUS, Z ; was it sync pulse ? incf state, f ; YES - enter state 1 return ; otherwise keep waiting for sync sync2 ; state 1: waiting for the second sync pulse clrf state movlw 3 subwf pulse, w ; Z=0: sync btfss STATUS, Z ; was it sync pulse ? return ; NO - keep waiting incf state, f ; YES - enter state 2 incf state, f clrf seconds ; reset seconds counter: 1 second has been passed incf seconds, f ; when a double sync is received movlw 9 ; prepare to receive 9 pulses movwf pulseNo return getByte call getBit ; analyse the received bit and shift it into addlw 0 ; the wwvb byte if accepted btfss STATUS, Z ; is byte complete ? return ; NO - wait for another bit movf state, w ; save the received byte wwvbByte andlw 0xF0 ; in one of time holding variables depending movwf temp ; on the byte number in temp swapf temp, f ; the byte numbers start with 1 movf wwvbByte, w decf temp, f btfsc STATUS, Z movwf minutes ; load minutes decf temp, f btfsc STATUS, Z call correctHours ; load hours decf temp, f btfsc STATUS, Z movwf days+1 ; load day # (first byte) decf temp, f btfsc STATUS, Z ; movwf days ; load day # (second byte) call computeDate decf temp, f btfsc STATUS, Z movwf year+1 ; load year (first byte) decf temp, f btfss STATUS, Z return movwf year ; load year (second byte) + leap info clrf state ; since the 59th sync bit is received incf state, f ; we return back to state 1 return getBit decf pulseNo, f ; update # of pulses to receive movlw 5 subwf pulseNo, w ; bit #5 is meaningless btfsc STATUS, Z retlw 1 ; ignore it movlw 3 ; if sync is received we either complete subwf pulse, w ; the byte or return back to state 0 btfss STATUS, Z goto addBit ; the received bit is not sync - process it movf state, w ; the received bit is sync - check for clrf state ; byte completion; in this case pulseNo=0 incf state, f movf pulseNo, f btfss STATUS, Z ; pulseNo = 0? retlw 1 ; NO - error; return to state 1 addlw 16 ; YES - update the byte number movwf state movlw 10 movwf pulseNo ; reset # of pulses to receive retlw 0 ; signal processing request to the caller addBit movlw 2 ; now we know that either 1 or 0 is received subwf pulse, w ; C = pulse rlf wwvbByte, f ; shift in the received bit retlw 1 getNoDays movf month, w addwf PCL, f retlw 31 ; January retlw 28 retlw 31 retlw 30 retlw 31 retlw 30 retlw 31 ; July retlw 31 retlw 30 retlw 31 retlw 30 retlw 31 ; December correctHours andlw 0x3F movwf hours movwf hours+1 ; copy CBD(hours) in hours+1 swapf hours+1, f ; convert hours+1 into binary rep movlw 0x0F andwf hours+1, w movwf hours+1 ; retrieve tens of hours bcf STATUS, C rlf hours+1, f rlf hours+1, f addwf hours+1, f ; hours+1 *= 5 rlf hours+1, f ; hours+1 *= 10 movf hours, w andlw 0x0F addwf hours+1, f ; conversion is complete movlw tZone ; correct hours wrt time zone btfsc year, 0 ; summer time correction addlw 1 addwf hours, f movlw 36 btfss STATUS, C addwf hours, f movlw -6 btfss STATUS, DC addwf hours, f return computeDate movwf days swapf days+1, w ; convert the day number from BCD into decimal andlw 0x03 ; we use Horner's schema movwf temp ; temp = hundreds of days bcf STATUS, C rlf temp, f rlf temp, f ; temp *= 4 addwf temp, f ; temp *= 5 rlf temp, f ; temp *= 10 movf days+1, w ; w = tens of days andlw 0x0F addwf temp, w ; w = temp = hund.*10 + tens movwf temp ; still an 8-bit value clrf temp+1 ; 16-bit multiply by 10 bcf STATUS, C rlf temp, f rlf temp, f rlf temp+1, f addwf temp, f btfsc STATUS, C incf temp+1, f ; temp *= 5 bcf STATUS, C rlf temp, f rlf temp+1, f ; *temp *= 10 swapf days, w andlw 0x0F addwf temp, f btfsc STATUS, C incf temp+1, f ; temp = decimal of days (2 bytes) movf temp, w ; decrement days # to make days counting btfsc STATUS, Z ; start with 0 decf temp+1, f decf temp, w movwf days movf temp+1, w movwf days+1 clrf month movlw tZone ; correct days # according to UTC time addwf hours+1, w btfsc STATUS, C goto cdLoop1 movf days, w btfsc STATUS, Z decf days+1, f decf days, f cdLoop1 call getNoDays ; w = # of days in a month movwf temp movf year, w ; check for leap year and increment andwf month, w ; the # of days in February andlw 1 ; leave only 1 bit btfss STATUS, Z incf temp, w ; temp = corrected # of days movf temp, w movwf temp+1 subwf days, f ; 16-bit subtract clrw clrf temp btfss STATUS, C incfsz temp, w subwf days+1, f incf month, f btfsc STATUS, C goto cdLoop1 movf temp+1, w addwf days, w ; days = day of the month addlw 1 movwf day movlw 10 ; convert month into BCD clrf temp cdLoop2 subwf month, f incf temp, f btfsc STATUS, C goto cdLoop2 addwf month, w decf temp, f swapf temp, f addwf temp, w movwf month movlw 10 ; convert date into BCD clrf temp cdLoop3 subwf day, f incf temp, f btfsc STATUS, C goto cdLoop3 addwf day, w decf temp, f swapf temp, f addwf temp, w movwf day return delay100msec ; a 100-msec delay movlw 64 movwf del movlw 195 addlw -1 btfss STATUS, Z goto $-2 decfsz del, f goto delay100msec+2 return ;##################### custom LCD interface updateLCD movlw b'10000000' ; move cursor home call writeLCD swapf hours, w andlw 0x03 addlw 48 ; ASCII conversion call writeLCD ; write tens of hours movf hours, w andlw 0x0F addlw 48 call writeLCD ; write units of hours movlw ':' call writeLCD swapf minutes, w andlw 0x07 addlw 48 ; ASCII conversion call writeLCD ; write tens of minutes movf minutes, w andlw 0x0F addlw 48 call writeLCD ; write units of minutes movlw ':' call writeLCD swapf seconds, w andlw 0x0F addlw 48 ; ASCII conversion call writeLCD ; write tens of seconds movf seconds, w andlw 0x0F addlw 48 call writeLCD ; write units of seconds movlw ' ' call writeLCD movlw 'C' call writeLCD movlw 'S' call writeLCD movlw 'T' call writeLCD movlw 0xC0 call writeLCD ; move cursor to the second line swapf month, w ; write month andlw 0x0F addlw 48 call writeLCD movf month, w andlw 0x0F addlw 48 call writeLCD movlw '/' call writeLCD swapf day, w ; write month andlw 0x0F addlw 48 call writeLCD movf day, w andlw 0x0F addlw 48 call writeLCD movlw '/' ; output year call writeLCD movlw '2' call writeLCD movlw '0' call writeLCD movf year+1, w andlw 0x0F addlw 48 call writeLCD swapf year, w andlw 0x0F addlw 48 call writeLCD ; movlw ' ' ; output leap and time saving info ; call writeLCD ; movf year, w ; andlw 0x09 ; addlw 48 ; call writeLCD return writeLCD ; write byte in W to the LCD bus movwf dataIO movlw b'011011' andwf GPIO, f movlw 0x85 ; setup FSR to point to TRISIO movwf FSR bsf INDF, SCL ; make sure that clock is high movlw 8 movwf cnt ; bits counter w_loop btfss GPIO, SCL ; wait for release of the clock line goto $-1 bcf INDF, SCL ; set clock low rlf dataIO, f ; get the rightmost data bit btfss STATUS, C bcf INDF, SDA btfsc STATUS, C bsf INDF, SDA ; now the data bit is on the line goto $+1 ; short delay bsf INDF, SCL ; raise clock up movlw 6 ; a 20 usec delay addlw -1 btfss STATUS, Z goto $-2 decfsz cnt, f goto w_loop ; repeat this 8 times return END