;------------------------------------------------------------------------------------------------------------------------ ; Source code for the PIC16F627 based Low Cost CPU Fan Speed Tester. ;------------------------------------------------------------------------------------------------------------------------ ; ; **Fan Tachometer ; TMR0 is the counter for the fan clock pulses. ; TMR1 is the timer to time every 0.5 seconds. ; ; **Output to CD4511 ; RB0 - RB3 for digits. ; RB4 - RB6 for 7 segment selector. ; ; RB4 - 2nd digit from the right. (Numbers in RPM) ; RB5 - 3rd digit from the right. ; RB6 - 4th digit from the right. ; RB7 - 1st digit from the right. (Random number XD) ; ; Instruction Cycle Time = 1 / (4MHz / 4) = 1us per instruction ;------------------------------------------------------------------------------------------------------------------------ LIST P=16F627 INCLUDE "p16f627.inc" ; ERRORLEVEL -302 __CONFIG _PWRTE_OFF & _HS_OSC & _WDT_OFF & _LVP_OFF & _BODEN_OFF; configuration switches CBlock 0x20 rmng_num ; Digit breaker registers. temp_num quotient N ; Delay registers. FIXDELAY digitfan0 ; Individual digit registers. digitfan1 digitfan2 digitfan3 prevdigitfan0 multiplier ; Manipulator storage registers. adder passer pulsetotal rdmhold prevfreq prevpulse EndC org 0x00 nop goto start org 0x04 goto ISR ; Interrupt Vector. start call initports call initTMRnINT awaitint call displayfanspd movf TMR1L, w ; Generate random number. movwf rdmhold movlw 0x0F andwf rdmhold, f goto awaitint ; Wait for interrupt to happen. ;------------------------------------------------------------------------------------------------------------------------ ; Subroutine to initialize the PORTs as Inputs or Outputs. ;------------------------------------------------------------------------------------------------------------------------ initports banksel PORTB clrf PORTB banksel TRISB ; Select TRISB bank. movlw 0x00 ; Define PORTB as Outputs. movwf TRISB return ;------------------------------------------------------------------------------------------------------------------------ ; Initialize Timer and Interrupts Subroutine. ;------------------------------------------------------------------------------------------------------------------------ initTMRnINT banksel INTCON ; Enable all unmasked interrupts and peripheral interrupts. movlw b'11000000' movwf INTCON banksel PIE1 ; Enable TMR1 overflow interrupt. movlw b'00000001' movwf PIE1 banksel OPTION_REG ; 1:1 Prescaler to TMR0, rising edge of the clock, Clock = RA4 Transition, TMR0 as counter. movlw b'11101000' movwf OPTION_REG banksel T1CON ; 1:8 Prescalar to TMR1, osc off, internal Fosc/4 clock, Enable TMR1. movlw b'00110001' movwf T1CON return ;------------------------------------------------------------------------------------------------------------------------ ; Interrupt Service Routine. (ISR) ;------------------------------------------------------------------------------------------------------------------------ ISR btfss PIR1, TMR1IF ; Check if TMR1 overflowed. goto intdone ; If no, return from interrupt. Else, service interrupts. beginISR bcf T1CON, TMR1ON ; Disable TMR1. bcf PIR1, TMR1IF ; Clear TMR1 interrupt flag. movf TMR0, w movwf prevfreq ; Pass TMR0 value to pulse counters. movwf rmng_num movwf pulsetotal movf prevpulse, w ; Adds previous fan speed value to current fan speed value and average the two. addwf rmng_num, f bcf STATUS, C ; Divides summed value by 2. rrf rmng_num, f call breakdigitfanspd ; Break pulse total to individual digits. call convertrpm ; Convert Hertz to RPM. movf prevfreq, w ; Pass previous counted frequency to prevpulse. movwf prevpulse clrf TMR1L ; Clear all timers. clrf TMR1H clrf TMR0 bsf T1CON, TMR1ON ; Re-enable TMR1. intdone retfie ;------------------------------------------------------------------------------------------------------------------------ ; N DELAY SUBROUTINE, delay in multiples of 200us up to 200us*255 = 51ms (or more) ;------------------------------------------------------------------------------------------------------------------------ NDELAY MOVWF N ; N is delay multiplier NOTOVER CALL DELAY200 ; Call for 200us DECFSZ N, 1 ; Decrease N by 1 GOTO NOTOVER ; The delay isn't done RETURN ;------------------------------------------------------------------------------------------------------------------------ ; FIXED 200us DELAY (Possibly more due to execution time of the DECFSZ instruction.) ;------------------------------------------------------------------------------------------------------------------------ DELAY200 MOVLW 0x42 ; 66 LOOPS MOVWF FIXDELAY ; 200us fixed delay NOTDONE200 DECFSZ FIXDELAY, 1 ; Decrement of FIXDELAY GOTO NOTDONE200 ; If 200us isn't up go back to NOTDONE200 RETURN ; If 200us is up then return to instruction. ;------------------------------------------------------------------------------------------------------------------------ ; Breaks down the temperature reading to its individual digits. ;------------------------------------------------------------------------------------------------------------------------ get_dig movlw d'10' ; To split the digits, divide them by 10. incf quotient, f ; Increment of quotient with each subtraction by 10. subwf rmng_num, f ; Subtract the number by 10. skpnc ; If already negative, stop division. goto get_dig ; Else, continue dividing. addwf rmng_num, f ; Restore number. decf quotient, f ; Restore quotient. movf rmng_num, w ; Move rmng_num to temp_num. movwf temp_num movf quotient, w ; Move quotient to rmng_num. movwf rmng_num movf temp_num, w return ;------------------------------------------------------------------------------------------------------------------------ ; Break down fanspeed to individual digits. ;------------------------------------------------------------------------------------------------------------------------ breakdigitfanspd clrf quotient call get_dig ; Get 1st digit. movwf digitfan0 clrf quotient call get_dig ; Get 2nd digit. movwf digitfan1 clrf quotient call get_dig ; Get 3rd digit. movwf digitfan2 return ;------------------------------------------------------------------------------------------------------------------------ ; Convert frequency to RPM. ;------------------------------------------------------------------------------------------------------------------------ convertrpm banksel multiplier ; Fan Speed in RPM = Fan Speed in Hz * 60 digitfanspd0x6 movlw d'6' movwf multiplier movf digitfan0, w movwf adder keepmult0 movf adder, w addwf digitfan0, f decfsz multiplier, f goto keepmult0 subwf digitfan0, f movlw d'10' keeppass0 incf passer, f subwf digitfan0, f skpnc goto keeppass0 addwf digitfan0, f decf passer, f digitfanspd1x6 movlw d'6' movwf multiplier movf digitfan1, w movwf adder keepmult1 movf adder, w addwf digitfan1, f decfsz multiplier, f goto keepmult1 subwf digitfan1, f movf passer, w addwf digitfan1, f clrf passer movlw d'10' keeppass1 incf passer, f subwf digitfan1, f skpnc goto keeppass1 addwf digitfan1, f decf passer, f digitfanspd2x6 movlw d'6' movwf multiplier movf digitfan2, w movwf adder keepmult2 movf adder, w addwf digitfan2, f decfsz multiplier, f goto keepmult2 subwf digitfan2, f movf passer, w addwf digitfan2, f clrf passer movlw d'10' keeppass2 incf passer, f subwf digitfan2, f skpnc goto keeppass2 addwf digitfan2, f decf passer, f spincheck movlw d'0' ; Checks if the fan is actually spinning. subwf pulsetotal, f skpnz goto notspinning goto spinning notspinning movlw d'0' ; If not spinning then write 0 to the last digit. movwf digitfan3 goto rpmconvdone spinning movlw d'10' ; If it is spinning display the generated random number. subwf rdmhold, f skpc addwf rdmhold, f movf rdmhold, w movwf digitfan3 goto rpmconvdone rpmconvdone clrf passer return ;------------------------------------------------------------------------------------------------------------------------ ; Display fan speed on 7 segment displays. ;------------------------------------------------------------------------------------------------------------------------ displayfanspd bsf PORTB, 4 ; Display digit0. bcf PORTB, 5 bcf PORTB, 6 bcf PORTB, 7 movf prevdigitfan0, w ; Obtain average value for digit0 from the current and previous values. addwf digitfan0, f bcf STATUS, C rrf digitfan0, f movlw 0xF0 ; Strip lower 4 bits. andwf PORTB, f movf digitfan0, w iorwf PORTB, f movf digitfan0, w ; Pass current digitfan0 value to previous value. movwf prevdigitfan0 movlw d'20' ; Small delay for viewing. call NDELAY bcf PORTB, 4 ; Display digit1. bsf PORTB, 5 bcf PORTB, 6 bcf PORTB, 7 movlw 0xF0 andwf PORTB, f movf digitfan1, w iorwf PORTB, f movlw d'20' ; Small delay for viewing. call NDELAY bcf PORTB, 4 ; Display digit2. bcf PORTB, 5 bsf PORTB, 6 bcf PORTB, 7 movlw 0xF0 andwf PORTB, f movf digitfan2, w iorwf PORTB, f movlw d'20' ; Small delay for viewing. call NDELAY bcf PORTB, 4 ; Display digit2. bcf PORTB, 5 bcf PORTB, 6 bsf PORTB, 7 movlw 0xF0 andwf PORTB, f movf digitfan3, w iorwf PORTB, f movlw d'20' ; Small delay for viewing. call NDELAY return ;------------------------------------------------------------------------------------------------------------------------ ; End of programme. ;------------------------------------------------------------------------------------------------------------------------ end