Here is my updated version of the driver code for this using the PIC16F628 as a drop in replacement for the F84 (F84 is also still supported). The other main changes are a switch to 4-bit LCD interface to free up some pins and USART output so the frequency can be fed to a PC COM port.
;****************************************************************************** ; FREQUENCY COUNTER ; Model : WTCNT ; Author : Barry Smith (tron at zoidberg dot nl) ; Date : April 2006 ; Version: 0.1 ; ; Adapted from original code by Terry J. Weeder (WWW.WEEDTECH.COM) ; ; The main differences between this code and the original code are: ; ; - Code ported to the 16F628 (should work on all 16F6xx chips) ; ; - Data also sent to USART port to allow PC to read frequency. ; ; - LCD interface modified to 4 data lines to free up I/O pins ; ; - Code uses MPASM include file for all register definitions ; ; - Various code tweaks and changes ; ; Distributed under the GNU public license. This code may be used in ; commercial products provided this source code is also made available. ; If this code is modified the modified source must be made available. ; ;****************************************************************************** IFDEF __16F84A include p16f84a.inc __CONFIG(_CP_OFF & _WDT_OFF & _PWRTE_ON & _XT_OSC) ENDIF IFDEF __16F628 include p16f628.inc __CONFIG(_BODEN_OFF & _CP_OFF & _DATA_CP_OFF & _PWRTE_ON & _WDT_OFF & _LVP_OFF & _MCLRE_OFF & _XT_OSC) #define SERIAL_OUT ; Send data via USART ENDIF ; #define NO_LCD ; Define to work without LCD present (eg RS232 only) ; #define LCD_8X2 ; LCD is an 8x2 screen LCD_E equ 0 ; Port A, bit 0 LCD_RW equ 1 ; Port A, bit 1 LCD_RS equ 2 ; Port A, bit 2 OVRFLW equ 7 IFDEF LCD_8X2 LCD_START equ 0x80 ; Start address on display ELSE LCD_START equ 0x82 ENDIF cblock 0x20 gate cnt1, cnt2, cnt3 calc1, calc2, calc3 sum1, sum2, sum3 rtcc2 DIGITS:0x07 count1 count2 in_reg addcnt status2 TBUF:0x0E ; Text Buffer TBUF_PTR ; Current position in tbuffer TSAVE ; Save INDF when using tbuffer TWTMP ; Also used in text buffering LW_HIGH LW_LOW endc ; org 0 goto start ; ; Writes a character to the end of the text buffer ; Preserves: W, FSR ; Destroys : STATUS tbuffer movwf TWTMP ; Save W movf FSR, W ; Save FSR movwf TSAVE movf TBUF_PTR, W ; Assign pointer to FSR movwf FSR movf TWTMP, W ; Write W value to pointer location movwf INDF incf TBUF_PTR, F ; Increment pointer.. incf FSR, F ; .. and null terminate string. clrf INDF movf TSAVE, W ; Restore FSR movwf FSR movf TWTMP, W ; restore W, in case its useful return ; ; Writes the contents of the tbuffer out tbuffer_out IFNDEF NO_LCD ; LCD only section movlw LCD_START call lcd_inst_out movlw TBUF movwf FSR tbo_loop movf INDF, W btfsc STATUS, Z goto tbo_out2 call lcd_data_out incf FSR, F goto tbo_loop ENDIF ; End LCD only section tbo_out2 IFDEF SERIAL_OUT movlw TBUF movwf FSR tbo_loop2 movf INDF, W btfsc STATUS, Z goto tbo_end call tx_data_out incf FSR, F goto tbo_loop2 tbo_end movlw '\n' ; Newline terminate call tx_data_out ENDIF return IFDEF SERIAL_OUT tx_data_out btfss PIR1, TXIF goto tx_data_out ; Wait for buffer to empty movwf TXREG return ENDIF ; int_del movlw 0x05 ;delay 2.5 ms (4 MHz clock) movwf count1 d1 movlw 0xA5 movwf count2 d2 decfsz count2 ,f goto d2 decfsz count1 ,f goto d1 retlw 0x00 ; sub bcf status2,OVRFLW ;clear overflow bit movf calc1,w ;subtract calc1 from cnt1 subwf cnt1 ,f btfsc STATUS,C goto sb1 movlw 0x01 ;borrow from cnt2 if overflow subwf cnt2 ,f btfsc STATUS,C goto sb1 subwf cnt3 ,f ;borrow from cnt3 if cnt2 overflow btfss STATUS,C bsf status2,OVRFLW ;set overflow bit if result is negative sb1 movf calc2,w ;subtract calc2 from cnt2 subwf cnt2 ,f btfsc STATUS,C goto sb2 movlw 0x01 ;borrow from cnt3 if cnt2 overflow subwf cnt3 ,f btfss STATUS,C bsf status2,OVRFLW ;set overflow bit if result is negative sb2 movf calc3,w ;subtract calc3 from cnt3 subwf cnt3 ,f btfss STATUS,C bsf status2,OVRFLW ;set overflow bit if result is negative retlw 0x00 ; add movf calc1,w ;add calc1 to cnt1 addwf cnt1 ,f btfss STATUS,C goto ad1 incfsz cnt2 ,f ;add to cnt2 if cnt1 overflow goto ad1 incf cnt3 ,f ;add to cnt3 if cnt2 overflow ad1 movf calc2,w ;add calc2 to cnt2 addwf cnt2 ,f btfsc STATUS,C incf cnt3 ,f ;add to cnt3 if cnt2 overflow movf calc3,w ;add calc3 to cnt3 addwf cnt3 ,f retlw 0x00 ; ; Begin by writing '/' (or 0x2F) to DIGITS+0 - 7 cnvt movlw 0x07 ;7 digits in display movwf count1 movlw DIGITS+0 ;set FSR for MSB in display movwf FSR movlw 0x2F ;one less that ASCII "0" cnvt0 movwf INDF incf FSR ,f decfsz count1,F goto cnvt0 movlw 0x0F ;load "1,000,000" in calc1-3 (0x0F4240) movwf calc3 movlw 0x42 movwf calc2 movlw 0x40 movwf calc1 cnvt1 call sub ;subtract number from count incf DIGITS+0 ,f ;increment 1,000,000's register movlw 0x3A xorwf DIGITS+0,w btfsc STATUS,Z goto overflow btfss status2,OVRFLW ;check if overflow goto cnvt1 call add ;add back last number movlw 0x01 ;load "100,000" in calc1-3 movwf calc3 movlw 0x86 movwf calc2 movlw 0xA0 movwf calc1 cnvt2 call sub ;subtract number from count incf DIGITS+1 ,f ;increment 100,000's register btfss status2,OVRFLW ;check if overflow goto cnvt2 call add ;add back last number clrf calc3 ;load "10,000" in calc1-3 movlw 0x27 movwf calc2 movlw 0x10 movwf calc1 cnvt3 call sub ;subtract number from count incf DIGITS+2 ,f ;increment 10,000's register btfss status2,OVRFLW ;check if overflow goto cnvt3 call add ;add back last number movlw 0x03 ;load "1,000" in calc1-3 movwf calc2 movlw 0xE8 movwf calc1 cnvt4 call sub ;subtract number from count incf DIGITS+3 ,f ;increment 1,000's register btfss status2,OVRFLW ;check if overflow goto cnvt4 call add ;add back last number clrf calc2 ;load "100" in calc1-3 movlw 0x64 movwf calc1 cnvt5 call sub ;subtract number from count incf DIGITS+4 ,f ;increment 100's register btfss status2,OVRFLW ;check if overflow goto cnvt5 call add ;add back number movlw 0x0A ;load "10" in calc1-3 movwf calc1 cnvt6 call sub ;subtract number from count incf DIGITS+5 ,f ;increment 10's register btfss status2,OVRFLW ;check if overflow goto cnvt6 call add ;add back last number movf cnt1,w ;put remainder in 1's register addwf DIGITS+6 ,f incf DIGITS+6 ,f retlw 0x00 ; count BANKSEL OPTION_REG movlw b'00110111' ;rtcc = ext, 1/256 movwf OPTION_REG BANKSEL TRISA movlw b'00010000' ;define PORTA as output movwf TRISA BANKSEL PORTA bcf PORTA,3 bcf PORTA,2 clrf cnt3 clrf TMR0 clrf rtcc2 bsf PORTA,2 ;toggle rtcc pin bcf PORTA,2 movf gate,w ;get gate time movwf count1 bsf PORTA,3 ;start count fr4 movlw 0xFA movwf count2 goto fr6 fr5 nop nop nop nop nop nop fr6 movf TMR0,w ;test for rtcc rollover (12) subwf rtcc2 ,f btfss STATUS,Z goto fr7 nop goto fr8 fr7 btfsc STATUS,C incf cnt3 ,f fr8 movwf rtcc2 nop nop nop decfsz count2 ,f goto fr5 decfsz count1 ,f goto fr4 bcf PORTA,3 ;stop count movf TMR0,w ;get rtcc count movwf cnt2 subwf rtcc2 ,f ;test for rtcc rollover btfss STATUS,C goto fr9 btfss STATUS,Z incf cnt3 ,f fr9 clrf cnt1 ;set to get prescaler count fr10 decf cnt1 ,f bsf PORTA,2 ;toggle rtcc pin bcf PORTA,2 movf TMR0,w ;test if rtcc has changed xorwf cnt2,w btfsc STATUS,Z goto fr10 retlw 0x00 ; ; IFNDEF NO_LCD lcd_data_out bsf PORTA, LCD_RS goto lcd_w_out lcd_inst_out bcf PORTA, LCD_RS ; ; 4 bit W out routine ; lcd_w_out movwf LW_HIGH movwf LW_LOW bcf PORTA, LCD_RW movlw b'00001111' ; Set RB7:4 as outputs BANKSEL TRISB andwf TRISB, F BANKSEL PORTB movlw b'11110000' andwf LW_HIGH, F movlw b'00001111' andwf LW_LOW, F swapf LW_LOW, F ; Now LW_HIGH = 7654xxxx, LW_LOW = 3210xxxx from orig. W movf PORTB, W andlw b'00001111' iorwf LW_HIGH, W movwf PORTB ; Writes high order bits out bsf PORTA, LCD_E nop bcf PORTA, LCD_E movf PORTB, W andlw b'00001111' iorwf LW_LOW, W movwf PORTB ; Writes low order bits out bsf PORTA, LCD_E nop bcf PORTA, LCD_E lcd_busy_wait call lcd_w_in movwf LW_HIGH btfss LW_HIGH, 7 goto lcd_shift goto lcd_busy_wait ; lcd_shift IFDEF LCD_8X2 movlw 0x08 xorwf LW_HIGH, W btfss STATUS, Z return movlw 0xC4 call lcd_inst_out ENDIF return ; ; Routine to read the BF/Addr information from the LCD ; lcd_w_in movlw b'11110000' ; Set RB7:4 as inputs BANKSEL TRISB iorwf TRISB, F BANKSEL PORTB bcf PORTA, LCD_RS nop ; Safety nop bsf PORTA, LCD_RW nop ; Safety nop bsf PORTA, LCD_E ; Trigger read (high bits) nop movf PORTB, W bcf PORTA, LCD_E ; Clock low movwf LW_HIGH bsf PORTA, LCD_E ; Trigger read (low bits) movlw b'11110000' andwf LW_HIGH, F swapf PORTB, W bcf PORTA, LCD_E andlw b'00001111' iorwf LW_HIGH, F bcf PORTA, LCD_RW movlw b'00001111' ; Reset RB7:4 as outputs BANKSEL TRISB andwf TRISB, F BANKSEL PORTB movf LW_HIGH, W return ENDIF ; end LCD only section ; ;****************************************************************************** ; START ;****************************************************************************** ; start clrf PORTA ;instruction, write, enable low IFDEF __16F628 movlw 0x07 movwf CMCON ENDIF movlw b'00010000' BANKSEL TRISA movwf TRISA BANKSEL PORTB clrf PORTB movlw b'00000110' ; For 628 RX/TX must be inputs BANKSEL TRISB movwf TRISB BANKSEL PORTB IFDEF SERIAL_OUT BANKSEL SPBRG movlw d'25' ; 9600 baud (with BRGH=1) movwf SPBRG BANKSEL TXSTA bcf TXSTA, SYNC bsf TXSTA, TXEN bsf TXSTA, BRGH BANKSEL RCSTA bsf RCSTA, SPEN ENDIF IFNDEF NO_LCD ; It is necessary to wait for 15ms after Vcc rises to ; 4.5V and 40ms after it rises to 2.7V. However, as we ; use PWRTE_ON which gives a 72ms delay, this should be ; fine and we should need no extra delay here. ; movlw b'00001111' ; Note: PORTA is low so RS & RW andwf PORTB,F ; are both 0. movlw b'00110000' ; Puts 0011 on lcd D7:D4 iorwf PORTB, F ; yes, this does mean 8 bit! bsf PORTA,LCD_E ; toggle enable nop bcf PORTA,LCD_E call int_del call int_del ; Wait at least 4.1ms (5ms here) bsf PORTA,LCD_E ; Send 8-bit initialise again... nop bcf PORTA,LCD_E movlw d'50' ; Now need 100us delay movwf TWTMP lcd_init_del1 decfsz TWTMP, F goto lcd_init_del1 ; about 150us in fact... bsf PORTA, LCD_E ; Yet again we set it to 8-bit nop ; what a wierd initialisation bsf PORTA, LCD_E ; this is! bcf PORTB, 4 ; Change 8 line -> 4 line nop bsf PORTA,LCD_E ; Finally we can send the 4-bit init nop bcf PORTA,LCD_E movlw d'15' ; Now need 40us delay movwf TWTMP lcd_init_del2 decfsz TWTMP, F goto lcd_init_del2 ; about 150us in fact... ; Finally we can send 4-bit instructions, starting with ; the yet another initialisation instruction. movlw b'00101000' ;initialise (again) call lcd_inst_out movlw b'00001100' ;display on, cursor off call lcd_inst_out movlw b'00000001' ;clear display call lcd_inst_out movlw b'00000110' ;entry mode call lcd_inst_out movlw b'10000000' ;cursor to start call lcd_inst_out ENDIF ; end LCD only section ; mhz movlw 0x14 ;0.1 sec gate movwf gate call count call cnvt ;convert binary to ASCII ; ; If first 2 digits are zeros, goto khz1, otherwise mhz1 ; movlw '0' ;test if "0" xorwf DIGITS+0,w btfss STATUS,Z goto mhz1 movlw '0' ;if 1st digit is 0... test if "0" xorwf DIGITS+1,w btfsc STATUS,Z goto khz1 mhz1 movlw TBUF ; Reset TBUF pointer movwf TBUF_PTR movlw 0x02 ;output first 2 characters movwf count1 movlw DIGITS+0 ;MSD of freq movwf FSR ; ; mhz2/mhz3 loop puts out 2 (count1) digits, printing spaces for leading zeros. ; mhz2 movlw '0' ;test if "0" xorwf INDF,w btfss STATUS,Z goto mhz3 movlw ' ' ;change preceeding "0's" to "space" call tbuffer incf FSR ,f decfsz count1 ,f goto mhz2 goto mhz4 mhz3 movf INDF,w call tbuffer incf FSR ,f decfsz count1,f goto mhz3 ; ; We know we're dealing with Mhz here, or we would have jumped to kHz ; by now, so put out '.' ; mhz4 movlw '.' call tbuffer movlw 0x05 ;output last 5 characters movwf count1 mhz5 movf INDF,w call tbuffer incf FSR ,f decfsz count1 ,f goto mhz5 movlw ' ' call tbuffer movlw 'M' call tbuffer movlw 'H' call tbuffer movlw 'z' call tbuffer movlw ' ' call tbuffer movlw ' ' call tbuffer call tbuffer_out goto mhz ; ; If first 2 digits were 00 then we try here for kHz ; khz movlw 0x14 ;0.1 sec gate movwf gate call count call cnvt ;convert binary to BCD movlw '0' ;test if 0 xorwf DIGITS+0,w btfss STATUS,Z goto mhz1 movlw '2' ;test if < 2 subwf DIGITS+1,w btfsc STATUS,C goto mhz1 movlw '0' ;test if "0" xorwf DIGITS+1,w btfss STATUS,Z goto khz1 movlw '0' ;test if "0" xorwf DIGITS+2,w btfsc STATUS,Z goto xkhz khz1 movlw TBUF ; Reset TBUF pointer movwf TBUF_PTR movlw 0x05 ; output first 5 characters movwf count1 movlw DIGITS+0 ; MSD of freq movwf FSR khz2 movlw '0' ; test if "0" xorwf INDF,w btfss STATUS,Z goto khz3 movlw ' ' ; change preceeding "0's" to "space" call tbuffer incf FSR ,f decfsz count1 ,f goto khz2 goto khz4 khz3 movf INDF,w call tbuffer incf FSR ,f decfsz count1 ,f goto khz3 khz4 movlw '.' call tbuffer movf INDF,w ;output last 2 characters call tbuffer incf FSR ,f movf INDF,w call tbuffer movlw ' ' call tbuffer movlw 'k' call tbuffer movlw 'H' call tbuffer movlw 'z' call tbuffer movlw ' ' call tbuffer movlw ' ' call tbuffer call tbuffer_out goto khz ; ; Now routines with modified 1 sec gates for < 100kHz ; xkhz movlw 0xC8 ;1 sec gate movwf gate call count call cnvt ;convert binary to BCD movlw '0' ;test if 0 xorwf DIGITS+0,w btfss STATUS,Z goto khz movlw '2' ;test if < 2 subwf DIGITS+1,w btfsc STATUS,C goto khz movlw '0' ;test if 0 xorwf DIGITS+1,w btfss STATUS,Z goto xkhz1 movlw '0' ;test if 0 xorwf DIGITS+2,w btfsc STATUS,Z goto hz0 xkhz1 movlw TBUF ; Reset TBUF pointer movwf TBUF_PTR movlw 0x04 ;output first 4 characters movwf count1 movlw DIGITS+0 ;MSD of freq movwf FSR xkhz2 movlw '0' ;test if "0" xorwf INDF,w btfss STATUS,Z goto xkhz3 movlw ' ' ;change preceeding "0's" to "space" call tbuffer incf FSR ,f decfsz count1 ,f goto xkhz2 goto xkhz4 xkhz3 movf INDF,w call tbuffer incf FSR ,f decfsz count1 ,f goto xkhz3 xkhz4 movlw '.' call tbuffer movf INDF,w ;output last 3 characters call tbuffer incf FSR ,f movf INDF,w call tbuffer incf FSR ,f movf INDF,w call tbuffer movlw ' ' call tbuffer movlw 'k' call tbuffer movlw 'H' call tbuffer movlw 'z' call tbuffer movlw ' ' call tbuffer movlw ' ' call tbuffer call tbuffer_out goto xkhz ; hz movlw 0xC8 ;1 sec gate movwf gate call count call cnvt ;convert binary to BCD movlw '0' ;test if "0" xorwf DIGITS+0,w btfss STATUS,Z goto xkhz1 movlw '0' ;test if "0" xorwf DIGITS+1,w btfss STATUS,Z goto xkhz1 movlw '2' ;test if < 2 subwf DIGITS+2,w btfsc STATUS,C goto xkhz1 hz0 movlw TBUF ; Reset TBUF pointer movwf TBUF_PTR movlw 0x07 ;output first 7 characters movwf count1 movlw DIGITS+0 ;MSD of freq movwf FSR hz1 movlw '0' ;test if "0" xorwf INDF,w btfss STATUS,Z goto hz2 movlw ' ' ;change preceeding "0's" to "space" call tbuffer incf FSR ,f decfsz count1 ,f goto hz1 goto hz3 hz2 movf INDF,w call tbuffer incf FSR ,f decfsz count1 ,f goto hz2 hz3 movlw ' ' call tbuffer movlw 'H' call tbuffer movlw 'z' call tbuffer movlw ' ' call tbuffer movlw ' ' call tbuffer movlw ' ' call tbuffer movlw ' ' call tbuffer call tbuffer_out goto hz ; overflow IFNDEF NO_LCD movlw 0x01 ;clear display call lcd_inst_out ENDIF movlw TBUF ; Reset TBUF pointer movwf TBUF_PTR movlw 'O' call tbuffer movlw 'v' call tbuffer movlw 'e' call tbuffer movlw 'r' call tbuffer movlw 'f' call tbuffer movlw 'l' call tbuffer movlw 'o' call tbuffer movlw 'w' call tbuffer call tbuffer_out IFNDEF NO_LCD movlw 0x02 ;cursor at home call lcd_inst_out ENDIF goto mhz ; end
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