Audio Frequency Counter

[charudatt]

Hello Steve,

I have run into some problem using your code for a 16F628A with a 16x2 LCD.

I am basically making a audio frequency counter, which would then be used to control a set of 8 LED's depending upon the Input frequency on PORTB.

Keeping this in mind I tried to output the frequency on the LCD but I get jumping figures at high speed. I believe , I have to introduce a delay between the display. Secondly , connecting 10K to ground on Pin#3 with 1K in series , as your circuit says, I don't get any reading. Which means , I need some impedence matching or may be a signal conditioner.

My audio source is from my desktop computer , audio out.

my code so far -

@   __CONFIG  _HS_OSC & _MCLRE_OFF  &  _LVP_OFF & _WDT_ON & _PWRTE_ON  & _BODEN_ON
DEFINE OSC 20

            ;76543210           
    TRISB = %00000000			
    TRISA = %11110000
 
DEFINE LCD_DREG PORTB 			'Define PIC port used for LCD Data lines
DEFINE LCD_DBIT 0 			    'Define first pin of portb connected to LCD DB4
DEFINE LCD_RSREG PORTB 			'Define PIC port used for RS line of LCD
DEFINE LCD_RSBIT 5 			    'Define Portb pin used for RS connection
DEFINE LCD_EREG PORTB 			'Define PIC prot used for E line of LCD
DEFINE LCD_EBIT 4 			    'Define PortB pin used for E connection
DEFINE LCD_BITS 4 			    'Define the 4 bit communication mode to LCD
DEFINE LCD_LINES 2 			    'Define using a 2 line LCD
'DEFINE LCD_COMMANDUS 2000 		'Define delay between sending LCD commands
'DEFINE LCD_DATAUS 50 			'Define delay time between data sent.

    
    ' Interrupt and register definition
    ' ---------------------------------
    '
    OPTION_REG = %1111000   ' TMR0 clock source : RA4/T0CKI
                            ' increment on low to high transition
                            ' Prescaler assign to WDT
                            ' WDT rate 1:1
                            '
    INTCON = %10100000      ' Enable global interrupt
                            ' Disable EE write interrupt
                            ' Enable TMR0 overflow interrupt
    CMCON = 7            ' disable analog comparator
    VRCON = 0            'turns off Vref for min current 

        
    ' Variable definition
    ' -------------------
    '
    DisplayPort  var PORTB   ' Port for 7 Segments     
    ClockInput   var PORTA.4 ' Input pin for signal
    _7Seg1       con 14      ' enable more significant 7 segment display
    _7Seg2       con 13      ' enable mid significant 7 segment display
    _7Seg3       con 11      ' enable less significant 7 segment display
    Digit_1	     var byte    ' Hundreds digit
    Digit_2	     var byte    ' Tenth digit
    Digit_3	     var byte    ' Unit digit
    ToBeDisplay	 var word    ' Result of count to be send to 7 segment display
    Display      var byte    ' Temp variable
    DisplayLoop  var byte    ' 
    Delay        var word    ' Variable for Delay loop
    OverFlowVar  var word	 '
    Thousands	 var bit	 ' Flag for count >= 1000 & < 10 000 
    TenThousands var bit	 ' Flag for count >= 10 000

    ' Variable and software initialisation
    ' ------------------------------------
    '
    tobedisplay = 0 ' set initial value of count
    TMR0 = 0        ' reset prescaller 
    on interrupt goto SetVarToBeDisplay
    
MainLoop:

    ' MainLoop
    ' ---------
    '
    ' 1. display the result of the count on RA4 pin
    ' 2. refresh display
    ' 3. reset Timer0 
    ' 4. reload prescaler.
    '
    ' Duration of the procedure : 1 sec 
    '           fine tuned by DelayBetweenEachDisplay Sub
    '
    ' Looping 1 sec and get results of the pulse count in
    ' TMR0 + OverFlowVar
    '
DisplayRefresh:
	'
    ' Testing amount of count
    ' -----------------------
    '
    ' Get the result of count and place decimal point flag
    ' on the according 7 segments
    '
    If tobedisplay>=1000 then
    	tobedisplay=tobedisplay/10
    	if tobedisplay>=1000 then
    		tobedisplay=tobedisplay/10
    		Thousands=0
    		TenThousands=1
    	else
    		TenThousands=0
    		thousands=1
    	endif
     else
    	thousands=0
    	tenthousands=0
    endif
    
    LCDOut $FE,$C0, "COUNT: ",DEC tobedisplay , "    " 
    gosub DelayBetweenEachDigit
    tobedisplay = OverFlowVar + TMR0
    OverFlowVar = 0 ' Reset OverFlowVar
    TMR0 = 0        ' reset prescaller

    goto DisplayRefresh
    goto DisplayRefresh
    goto DisplayRefresh
    goto DisplayRefresh
    goto DisplayRefresh
    goto DisplayRefresh


DelayBetweenEachDigit:

    ' DelayBetweenEachDigit
    ' ---------------------
    ' Produce delay of about 3 mSec 
    '
    ' Fine tuned with MPLAB StopWatch to get MainLoop = 1 sec
    '
	for delay=1 to 307
	    @ nop
	next
	@ nop
	@ nop
	@ nop
	@ nop
	@ nop
	@ nop
	@ nop
    return


    disable
SetVarToBeDisplay:
    '
    ' SetVarToBeDisplay
    ' -----------------
    ' interrupt routine of TMR0 overflow
    '
    ' Reset prescaller
    ' Reset overflow flag
    '
    OverFlowVar = OverFlowVar + 256 
    INTCON.2 = 0 ' clear overflow flag
    TMR0 = 0     ' reload TMR0
    resume
enable