Frequency detection (audio)

[HankMcSpank]

Hi Bert,

I re-enabled hserout out in the ISR again, and these are the TMR1 counts I'm getting for successive comparator2 interrupts with an audio input of 82.4Hz (the lowest note/frequency on a standard tuning electric guitar)...

42947
42995
42946
42998
42944
43003
42960
43012
42964
43022
42974
43032
42991
42948
18932
18559
42953
43012
42955
43005
42957
43001
42943


A couple of dodgy ones in there, but those aside, the TMR1 counts are coming in lower at about 43,000?

@ __CONFIG _CONFIG1, _FCMEN_OFF & _FOSC_INTOSC & _WDTE_OFF & _MCLRE_OFF & _CP_ON & _IESO_OFF & _BOREN_OFF & _PWRTE_OFF
@ __CONFIG _CONFIG2, _PLLEN_OFF & _STVREN_OFF & _LVP_OFF 
DEFINE  OSC 16
INCLUDE "DT_INTS-14.bas"     
INCLUDE "ReEnterPBP.bas"     ' Include if using PBP interrupts
DEFINE HSER_RCSTA 90h ' Enable serial port & continuous receive
DEFINE HSER_TXSTA 20h ' Enable transmit, BRGH = 0
DEFINE HSER_CLROERR 1 ' Clear overflow automatically
DEFINE HSER_SPBRG 25  ' 38400 Baud @ 16MHz, 0.16%
SPBRGH = 0
BAUDCON.3 = 1         ' Enable 16 bit baudrate generator
'16F1828 Pin settings....
' PIN# NAME     USE & CONNECTION
           '  1   Vdd      +5VDC power supply
TRISA.5 = 0'  2   RA5      
TRISA.4 = 1'  3   RA4      
TRISA.3 = 1'  4   RA3      
TRISC.5 = 0'  5   RC5      
TRISC.4 = 0'  6   RC4      C2OUT 
TRISC.3 = 1'  7   RC3         
TRISC.6 = 0'  8   RC6           
TRISC.7 = 0'  9   RC7      
TRISB.7 = 0'  10  RB7       
TRISB.6 = 1'  11  RB6       
TRISB.5 = 1'  12  RB5       
TRISB.4 = 1'  13  RB4       
TRISC.2 = 1'  14  RC2      
TRISC.1 = 1'  15  RC1      C12IN1- (FREQ DETECT)
TRISC.0 = 1'  16  RC0      
TRISA.2 = 0'  17  RA2               
TRISA.1 = 0'  18  RA1      
TRISA.0 = 0'  19  RA0      
'             20  Vss      Ground
ANSELA     = 0 
ANSELC     = 0   
          
APFCON0.2 = 0  'put hserout onto RB7 pin 10 (Pickit 2 RX pin)
  
'-------------------------------------------------------------------------
Osccon = %01111010   'sets the internal oscillator 
CPSCON0 = 0    ' capacitive sense module off
CM1CON0 = 0     ' comparator1 module off
CM2CON0.7 = 1 ' comparator2 on.
CM2CON0.5 = 1   'enable the output on a pin
CM2CON0.4 = 1 'invert the polarity
CM2CON0.1 = 1   'ENABLE HYSTERISIS
CM2CON1.7 = 1' enable interrupts on _+ve going transition
CM2CON1.5 = 0   ' set comparator comparison input pin to the DAC
CM2CON1.4 = 1   ' set comparator comparison input pin to the DAC
CM2CON1.1 = 0   'SELECT C12IN1- (PIN 15, RC1)
CM2CON1.0 = 1   'SELECT C12IN1- (PIN 15, RC1)

DACCON0.7 = 1 ' DAC ON
DACCON0.6 = 1 ' DAC ON
DACCON0.5 = 0  'put the output of the DAC o the DAC out pin
DACCON0.3 = 0   'SET DAC +VE REFERENCE REFERENCE TO VCC
DACCON0.2 = 0   'SET DAC +VE REFERENCE REFERENCE TO VCC
DACCON1 = %00000001   'sets the DAC voltage output to be very low (to use for the comparator to compare against.
OPTION_REG.7 = 0
ASM
INT_LIST  macro ; IntSource,    Label,         Type, ResetFlag?
    INT_Handler  CMP2_INT,  _CMP2_Interrupt,  ASM,  YES 
    endm
    INT_CREATE       ; Creates the interrupt processor
ENDASM
TMR1 = 0
T1CON = %00000111
@ INT_ENABLE CMP2_INT   ; Enable 'Int On Change' interrupts
loop1:
PAUSE 1
GOTO loop1

'Interrupt+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++

CMP2_Interrupt:   ' COMPARATOR2 INTERRUPT.
@ INT_DISABLE CMP2_INT
BSR=0
hserout [dec tmr1,13,10] 
toggle portc.7
TMR1=0
@ INT_ENABLE CMP2_INT
@ INT_RETURN