PIC16F84A Tachometer LED routine

[ThaSanta]

'****************************************************************
'*  Name    : RPM.BAS                                           *
'*  Author  : Christian Lerche                                  *
'*  Notice  : Copyright (c) 2009 DSB El-teknik                  *
'*          : All Rights Reserved                               *
'*  Date    : 28-05-2009                                        *
'*  Version : 1.0                                               *
'*  Notes   : PIC16F913, Boden Off, WDT off, PWR off            *
'*          :                                                   *
'****************************************************************
'
' Includes
'

'
' Defines-----------------------------------------------------------------------
'
    Define  osc 10                          ' Define oscillator XT 10 MHz
    DEFINE  ADC_BITS 10                     ' Define A/D Converter 10 bit
    DEFINE  ADC_CLOCK 3                     ' Define ADC clock source 
    DEFINE  ADC_SAMPLEUS 50                 ' Wait 50 µS before convert to digi
'
' INPUT / OUTPUT----------------------------------------------------------------
'
    TRISA = 0                               ' PORTA is output
    TRISA.5 = 1                             ' PORTA.5 is input
    TRISB = 1                               ' PORTB is input
    TRISC = 0                               ' PORTC is Output
    TRISB.0 = 1                             ' B0 / Int is count input
    ADCON0 = %10010001                      ' ADC On, right justified
    ADCON1 = 0                              ' ADC Freq = 625KHz
    ASM                                     ; Insert ASM
    BANKSEL LCDCON                          ; LCD Configuration
    CLRF    LCDCON                          ; Turn off LCD Driver
    ENDASM                                  ; End of ASM
'
' Variables and constants-------------------------------------------------------
'
    W1  VAR WORD                            ' W1 is 16 bit variable
    W2  var word                            ' W2 is 16 bit variable 
    W3  var word                            ' W3 is 16 bit variable
    B0  var byte                            ' B0 is 8 bit variable 
'
' Main program------------------------------------------------------------------
'
Main:
    ADCIN 4, W2                             ' Read Freq-to-voltage device
    W3 = W2 * 9774                          ' 9999 / 1023 = 9.774
    W1 = DIV32 1000                         ' Put the result in W1
    GOSUB GETNUM                            ' Show RPM
    Goto Main                               ' Do this forever
    END                                     ' For the compilers sake       
'
' Subroutines-------------------------------------------------------------------
' 
GETNUM:
    IF W1 >= 1000   THEN display4
    IF W1 >= 100    THEN display3
    IF W1 >= 10     THEN display2
    IF W1 >= 0      THEN display1
display4:
    B0 = W1 / 1000	                        ' Find number of thousands
	W1 = W1 // 1000	                        ' Remove thousands from W1
    Lookup B0,[$3F,$06,$5B,$4F,$66,$6D,$7D,$07,$7F,$67],B0
    PORTC = B0      	                    ' Send segments to LED
	PORTA = $01     	                    ' Turn on fourth digit
	Pause 1		                            ' Leave it on 1 ms
	PORTA = $00	                            ' Turn off digit to prevent ghosting 
display3:
	B0 = W1 / 100	                        ' Find number of hundreds
	W1 = W1 // 100	                        ' Remove hundreds from W1
	Lookup B0,[$3F,$06,$5B,$4F,$66,$6D,$7D,$07,$7F,$67],B0
	PORTC = B0	                            ' Send segments to LED
	PORTA = $02	                            ' Turn on third digit
	Pause 1		                            ' Leave it on 1 ms
	PORTA = $00     	                    ' Turn off digit to prevent ghosting 
display2
	B0 = W1 / 10	                        ' Find number of tens
	W1 = W1 // 10	                        ' Remove tens from W1
	Lookup B0,[$3F,$06,$5B,$4F,$66,$6D,$7D,$07,$7F,$67],B0
	PORTC = B0      	                    ' Send segments to LED
	PORTA = $04  	                        ' Turn on second digit
	Pause 1		                            ' Leave it on 1 ms
	PORTA = $00	                            ' Turn off digit to prevent ghosting 
display1
	B0 = W1		                            ' Get number of ones
    Lookup B0,[$3F,$06,$5B,$4F,$66,$6D,$7D,$07,$7F,$67],B0
	PORTC = B0	                            ' Send segments to LED
	PORTA = $08     	                    ' Turn on first digit
	Pause 1		                            ' Leave it on 1 ms
    PORTA = $00	                            ' Turn off digit to prevent ghosting     
    RETURN                                  ' Return to caller!

Here's the code for the project. I've made it, so it doesn't show the zeroes before the actual RPM.

I hope some of you can use it. Later I'll post the schematic for F/V converter

** EDIT **


Here's the schematic for the F/V Converter. For the 8V source, i use a small regulator, so that the car can run between 12 and 13.8 V at the battery. Depending on the source to the converter, the potentiometer is turned, until satisfied. Mine will run of the 12V to the ignition coil, so that i have 4 pulses for one revolution of the engine.
Depending on your choice of pulses, you may use a Frequency generator, at square-wave, and if your car pulses 4 times per revolution, then adjust it, until you get 5V out, at 4*166.66.
If the car pulses once per revolution, set your frequency generator to 166.66 (mine was digital), and adjust the potentiometer until 5V is reached.

You've now succesfully made a digital tachometer, that updates faster than the code could ever do, by it self.

Good luck, and have fun all of you!