;|------------------------------------------------------------------------| ;| CONTENTS : Simple low-cost 7-digit frequency meter using a PIC16F84 | ;| COPYRIGHT: Peter Halicky OM3CPH | ;| AUTHORS : Peter Halicky OM3CPH & Peter Halicky Jr., OM2PH ex OM2APH | ;| PCB : Tibor Madarasz OM2ATM | ;|------------------------------------------------------------------------| ;| E-Mail: peter@halicky.sk | ;| | ;| Bratislava, Slovakia, February, 1998, debugged & revised February, 2000| ;|------------------------------------------------------------------------| ;| This is 7-digit frequency meter counting up to 35 MHz. The decimal | ;| point is after MHz digit, but can be set at any position. Two dots can | ;| be set too (timing formula will change!). | ;| | ;| Power consumption with calculator display: 2.5V/9mA, 3V/13mA, 5V/35mA. | ;| | ;| Hardware is very simple: | ;| | ;| It contains : PIC 16F84 | ;| 4051 (BCD -> 1 of 8 decoder) | ;| 8 NPN low power Si transistors, | ;| 7-digit calculator display (common cathode), | ;| some resistors, capacitors and 2 switching diodes | ;| | ;| Note: | ;| "Calculator display" means (say) 7 digit LED multiplexed display. | ;| Both common cathode and common anode can be used. Software is written | ;| for both common cathode and common anode display. For common anode | ;| displays it requires very slight software (uncomment what is commented | ;| and comment what isn't...;-) and hardware modification (switching | ;| transistors are PNP instead NPN, ther emiters are connected with +5V | ;| and also pin No.3 of 4051 should be grounded). | ;| | ;| PIC is used as 3 byte counter. If it counts 0.1 s maximum measured | ;| frequency is FF FF FF, e. g. 167.77215 MHz (theoretically). | ;| | ;| In reality the maximum measured frequency will not exceed 50 MHz | ;| what is maximum input frequency of PIC precounter. But real one is | ;| around 27 MHz and with 1/6 of 74HC14 (Schmitt trigger) up to 38 MHz. | ;| | | | ;| +-+ +-+ | ;| | | | | | ;| | 470| | 470 | | | ;| | | | | | | ;| | +-+ +---\ +-+ | ;| RA4 | +------+ | | | | | ;| RA3 |--| 470 |-+--| +0-+-\ | ;| RA2 | +------+ | | \|___ | ;| ------+ +---/ /| | ;| V | ;| | | ;| --- | ;|------------------------------------------------------------------------| ;| | ;| The scale uses internal prescaler of PIC as low byte of counter, | ;| TMR0 as middle byte and some register as high byte of counter. The | ;| software DOESN'T read anything from any input port. RA4 is used as | ;| prescaler input. | ;| | ;|------------------------------------------------------------------------| ;| | ;| Measuring period is 100 000 us. | ;| Procesor cycle is T = 4/Fx us [MHz], fx is Xtal frequency | ;| | ;| Number of procesor cycles per measuring period: | ;| | ;| N = 100 000/T procesor cycles | ;| N = Fx * 100 000/4 = 25 000 * Fx | ;| | ;| The main steps of measuring period: | ;| | ;| 1. start measurement, | ;| 2. precode decimal value of digit to segments, | ;| 3. if it's 5th digit set decimal point, | ;| 4. output to PortB, | ;| 5. output digit number to PortA | ;| (numbers from left to right are 6543210), | ;| 6. test TMR0 overflow bite, if YES increase TimerH, | ;| 7. leave digit to light, | ;| 8. increase digit number, | ;| 9. if <7 goto 2, | ;| 10. else zero digit number, decrease counter and goto 2, | ;| 11. stop measurement, | ;| 12. shift out precounter content, | ;| 13. in case of digital scale add/substract RF, | ;| 14. precode 3-byte value into 7 decimal numbers, | ;| 15. goto 1 | ;| | ;|------------------------------------------------------------------------| ;| | ;| Total timing formula: | ;| | ;| N = 25 000 * Fx = 60*[7*(36 + 3*T1) + 6 + 3*T2] + 12 + 3*T3 + Z | ;| | ;| where T1,T2,T3 are initial values of timing loops, | ;| Z are additional tunig NOPs, | ;| Fx Xtal frequency in MHz. | ;| | ;|------------------------------------------------------------------------| ;| Some ideas were taken from "Simple low-cost digital frequency meter | ;| using a PIC 16C54" (frqmeter.asm) | ;| written by James Hutchby, MadLab Ltd. 1996 | ;|------------------------------------------------------------------------| ;| | ;| This software is free for private usage. It was created for HAM radio | ;| community members. Commercial exploatation is allowed only with | ;| permission of authors. | ;| | ;|------------------------------------------------------------------------| ; include include ;-------------------------------------------------------------------------- Index equ 0Ch ; dummy register Count equ 0Dh ; inkremental register Help equ 0Eh ; dummy register LED0 equ 0Fh LED1 equ 010h LED2 equ 011h LED3 equ 012h LED4 equ 013h LED5 equ 014h LED6 equ 015h LED7 equ 016h TimerH equ 017h ; higher byte of SW counter LowB equ 018h ; low byte of resulted frequency MidB equ 019h ; middle byte of resulted frequency HigB equ 01Ah ; high byte of resulted frequency Temp equ 01Bh ; temporary register HIndex equ 01Ch ; index register LEDIndex equ 01Dh ; LED pointer ;-------------------------------------------------------------------------- include ; timing loop values ;-------------------------------------------------------------------------- org 0 Start clrf Index clrf LEDIndex clrf LED0 clrf LED1 clrf LED2 clrf LED3 clrf LED4 clrf LED5 clrf LED6 clrf LED7 clrf LowB clrf MidB clrf HigB bsf STATUS,RP0 movlw b'00010000' ; RA0..RA3 outputs movwf TRISA ; RA4 input movlw b'00000000' ; RB0..RB7 outputs movwf TRISB clrwdt ; movlw b'00100111' ; Prescaler -> TMR0, movwf OPTION_REG ; 1:256, rising edge bcf STATUS,RP0 ; goto Go ; line 370 ;+-------------------------------------------------------------------------+ ;| The block of subroutines and constants tables | ;+-------------------------------------------------------------------------+ ;+-------------------------------------------------------------------------+ ;| 3 byte substraction of the constant from the table, it sets carry | ;| if result is negative | ;+-------------------------------------------------------------------------+ Subc24 clrf Temp ; it will temporary save CF movf Index,W ; pointer to low byte of constant movwf HIndex ; W -> HIndex call DecTable ; W returned with low byte of constant bsf STATUS,C ; set CF subwf LowB,F ; LowB - W -> LowB ; if underflow -> C=0 btfsc STATUS,C goto Step1 bsf STATUS,C movlw 1 subwf MidB,F ; decrement MidB ; if underflow -> C=0 btfsc STATUS,C goto Step1 bsf STATUS,C movlw 1 subwf HigB,F ; decrement HigB btfsc STATUS,C ; if underflow -> C=0 goto Step1 bsf Temp,C ; set C Step1 decf HIndex,F movf HIndex,W ; pointer to middle byte of const call DecTable bsf STATUS,C subwf MidB,F ; MidB - W -> MidB btfsc STATUS,C ; if underflow -> C=0 goto Step2 bsf STATUS,C movlw 1 subwf HigB,1 ; decrement HigB btfsc STATUS,C ; if underflow -> C=0 goto Step2 bsf Temp,C ; set C Step2 decf HIndex,F movf HIndex,W ; pointer to middle byte of constatnt call DecTable bsf STATUS,C subwf HigB,F ; HigB - W -> HigB btfsc STATUS,C ; if underflow -> C=0 goto ClearCF bsf STATUS,C goto SubEnd ClearCF rrf Temp,C ; C -> STATUS SubEnd retlw 0 ;+-------------------------------------------------------------------------+ ;| 3 byte addition of the constant from the table, it sets carry if | ;| result overflows | ;+-------------------------------------------------------------------------+ Addc24 clrf Temp ; register for temporary storage of CF movf Index,W ; pointer to lower byte of const into W movwf HIndex ; save it into HIndex call DecTable ; W contains low byte of const bcf STATUS,C ; clear C addwf LowB,1 ; W + LowB -> LowB btfss STATUS,C ; test overflow goto Add2 bcf STATUS,C ; clear C movlw 1 addwf MidB,F ; increment MidB btfss STATUS,C goto Add2 bcf STATUS,C movlw 1 addwf HigB,F ; increment HigB btfss STATUS,C ; test overflow goto Add2 bsf Temp,C ; store C Add2 decf HIndex,F ; pointer to middle byte into W movf HIndex,W call DecTable bcf STATUS,C addwf MidB,1 ; W + MidB -> MidB btfss STATUS,C goto Add3 bcf STATUS,C ; clear C movlw 1 addwf HigB,1 ; increment HigB btfss STATUS,C goto Add3 bsf Temp,C Add3 decf HIndex,F ; pointer to higher byte into W movf HIndex,W call DecTable bsf STATUS,C addwf HigB,F ; W + HigB -> HigB, btfss STATUS,C goto ClarCF bsf STATUS,C goto AddEnd ClarCF rrf Temp,C ; C -> STATUS AddEnd retlw 0 ;+------------------------------------------------------------------------+ ;| Tables of 3-byte constants | ;+------------------------------------------------------------------------+ ;| Table of decades | ;+------------------------------------------------------------------------+ DecTable addwf PCL,F ; W + PCL -> PCL retlw 0 ; 10 retlw 0 ; retlw 0Ah ; retlw 0 ; 100 retlw 0 ; retlw 064h ; retlw 0 ; 1 000 retlw 03h ; retlw 0E8h ; retlw 0 ; 10 000 retlw 027h ; retlw 010h ; retlw 01h ; 100 000 retlw 086h ; retlw 0A0h ; retlw 0Fh ; 1 000 000 retlw 042h ; retlw 040h ; ;+-----------------------------------------------------------------------+ ;| Table for conversion BCD -> 7 segments | ;+-----------------------------------------------------------------------+ LEDTable addwf PCL,F ; W + PCL -> PCL retlw b'00111111' ; ..FEDCBA = '0' retlw b'00000110' ; .....CB. = '1' retlw b'01011011' ; .G.ED.BA = '2' retlw b'01001111' ; .G..DCBA = '3' retlw b'01100110' ; .GF..CB. = '4' retlw b'01101101' ; .GF.DC.A = '5' retlw b'01111101' ; .GFEDC.A = '6' retlw b'00000111' ; .....CBA = '7' retlw b'01111111' ; .GFEDCBA = '8' retlw b'01100111' ; .GF..CBA = '9' retlw b'10000000' ; H....... = '.' ;It follows COMMON ANODE data table ;LEDTable addwf PCL,F ; W + PCL -> PCL ; retlw b'11000000' ; ..FEDCBA = '0' ; retlw b'11111001' ; .....CB. = '1' ; retlw b'10100100' ; .G.ED.BA = '2' ; retlw b'10110000' ; .G..DCBA = '3' ; retlw b'10011001' ; .GF..CB. = '4' ; retlw b'10010010' ; .GF.DC.A = '5' ; retlw b'10000010' ; .GFEDC.A = '6' ; retlw b'11111000' ; .....CBA = '7' ; retlw b'10000000' ; .GFEDCBA = '8' ; retlw b'10011000' ; .GF..CBA = '9' ; retlw b'01111111' ; H....... = '.' ;+------------------------------------------------------------------------+ ;| The main cycle entry point | ;+------------------------------------------------------------------------+ ;| Routine for conversion of 3-byte number into 7 digits | ;+------------------------------------------------------------------------+ Go bsf STATUS,RP0 movlw b'00000000' movwf TRISB bcf STATUS,RP0 movlw 6*3-1 ; pointer to dec. table movwf Index ; 6*3-1 -> Index movlw 9 ; maximum of substractions movwf Count ; 9 -> Count clrf Help movlw 6 movwf LEDIndex Divide call Subc24 ; substract untill result is negative, btfsc STATUS,C ; add last substracted number goto Add24 ; next digit incf Help,F decf Count,F btfss STATUS,Z goto Divide movlw 3 subwf Index,F goto Next Add24 call Addc24 movlw 3 subwf Index,F Next movlw 9 movwf Count movlw LED1 ; LED1 -> W addwf LEDIndex,W ; LED1 + LEDIndex -> W movwf Temp decf Temp,F ; LEDIndex+LED1-1 -> TEMP movf Temp,W movwf FSR ; W -> FSR movf Help,W ; Help -> W clrf Help ; save result at LEDx movwf INDF ; W -> LED(6..1) decf LEDIndex,F movlw 1 addwf Index,W btfss STATUS,Z goto Divide movf LowB,W movwf LED0 ; the rest -> LED0 ;+-----------------------------------------------------------------------+ ;| Registers LED0..LED6 are filled with values | ;+-----------------------------------------------------------------------+ clrf TimerH clrf TMR0 nop nop clrf LEDIndex movlw .60 ; set initial counter value movwf Index ; 60 -> Index clrf INTCON ; global INT disable, TMR0 INT disable ; clear TMR0 overflow bite ;+---------------------------------------------------------------------+ ;| Start of the measurement: RA3 + RA4 set input | ;+---------------------------------------------------------------------+ movlw b'00010000' ; all ports set L, RA4 set H movwf PORTA bsf STATUS,RP0 movlw b'00011000' ; RA0..RA2 output, RA3, RA4 input movwf TRISA bcf STATUS,RP0 ;+-----------------------------------------------------------------------+ ;| 7-step cycle of digits | ;+-----------------------------------------------------------------------+ LEDCycle movlw LED0 addwf LEDIndex,W ; LED1 + LEDIndex -> W movwf FSR ; W -> FSR movf INDF,W ; LED(0..6) -> W call LEDTable ; W contains segments movwf Temp ; test for decimal point movlw 5 bsf STATUS,Z subwf LEDIndex,W btfss STATUS,Z goto NoDot bsf Temp,7 ; common cathode.... ; bcf Temp,7 ; common anode.... NoDot movf Temp,W movwf PORTB ; segments -> PORTB movf LEDIndex,W ; LEDIndex -> W nop movwf PORTA ; digit number -> PORTA ;+------------------------------------------------------------------------ ;Test for TMR0 overflow ;+------------------------------------------------------------------------ btfss INTCON,2 ; Test for TMR0 overflow goto DoNothing incf TimerH,F ; YES! Increment SW counter bcf INTCON,2 ; clear overflow bite goto O_K DoNothing nop nop nop ;+-----------------------------------------------------------------------+ ;| The first timing loop 2+3*T1 procesor cycles | ;+-----------------------------------------------------------------------+ O_K movlw T1 movwf Temp Pause decfsz Temp,F goto Pause nop ;+-----------------------------------------------------------------------+ ;| The end of one digit processing | ;+-----------------------------------------------------------------------+ incf LEDIndex,F movlw 7 ; is 7th? bcf STATUS,Z subwf LEDIndex,W btfss STATUS,Z goto LEDCycle ; next digit nop ;+-----------------------------------------------------------------------+ ;| The second timing loop 2+3*T2 procesor cycles | ;+-----------------------------------------------------------------------+ movlw T2 movwf Temp Again decfsz Temp,F goto Again nop ;+-----------------------------------------------------------------------+ ;| The end of one 7-digits processing | ;+-----------------------------------------------------------------------+ clrf LEDIndex decfsz Index,F goto LEDCycle ; next 7 * LED nop ;+-----------------------------------------------------------------------+ ;| The third timing loop 2+9*T3+Z procesor cycles | ;+-----------------------------------------------------------------------+ movlw T3 movwf Temp EndPause decfsz Temp,F goto EndPause nop include ; nop ; Z times NOP ; nop ; 60 * (6 + 7 * (36 + 3*T1) + 3*T2) + 2 + 3*T3 + Z ; ------------------------------------------------------------------------ ; Final test for TMR0 overflow ; ------------------------------------------------------------------------ btfss INTCON,2 ; 1 goto Nothing2Do ; 3 incf TimerH,F ; 3 bcf INTCON,2 ; 4 goto Nx ; 6 Nothing2Do nop ; 4 nop ; 5 nop ; 6 60 * (6 + 7 * (36 + 3*T1) + 3*T2) + 8 + 3*T3 + Z ;+---------------------------------------------------------------------+ ;| Stop of the measurement: RA3 set output RA4 set input | ;+---------------------------------------------------------------------+ Nx clrw ; For common cathode ;Nx movlw b'11111111' ; For common anode movwf PORTB movlw b'00010000' ; RA0..RA3 = 0 movwf PORTA ; W -> PORTA bsf STATUS,RP0 movlw b'00010000' ; RA0..RA3 output movwf TRISA ; RA4 input bcf STATUS,RP0 btfsc INTCON,2 ; really final check incf TimerH,F bcf INTCON,2 ;+-----------------------------------------------------------------------+ ;| Analyse precounter and store counted value in registers | ;+-----------------------------------------------------------------------+ movf TMR0,W movwf MidB ; TMR0 -> MidB movf TimerH,W movwf HigB ; TimerH -> HigB clrf Temp CountIt incf Temp,F bsf PORTA,3 ; _| false impulz bcf PORTA,3 ; |_ bcf INTCON,2 movf TMR0,W ; actual TMR0 -> W bcf STATUS,Z subwf MidB,W btfsc STATUS,Z goto CountIt incf Temp,F comf Temp,F incf Temp,F incf Temp,W movwf LowB ;-------------------------------------------------------------------------- goto Go ;|------------------------------------------------------------------------| ;| The main cycle end | ;|------------------------------------------------------------------------| end