Measuring audio phase shift through a circuit with a PIC

[HankMcSpank]

Ok. I've hit a wall - & I can't get passed it - I need a leg up!

Te recap, I'm using a PIC to measure frequency (80Hz thru 1.4Khz) by counting the number of clock pulses between successive comparator interrupts. It works well.

I now need to measure phase shift .....but how to actually use the PIC hardware options available, to detect the amount of clock pulse between the non phase shifted signal & phase shifted signal's leading edges?

Here's a schematic of my test circuit...



I detect frequency as follows...

DT's Comp1 interrupt - start a timer
DT's Comp1 interrupts again - stop a timer.

so want to add in phase shift detect by bringing in another timer and measuring the clock counts until the second (lagging) signal's leading edge arrives, therefore the enlarged picture....

Comp1 interrupt - start a timer
Comp1 interrupts again - stop a timer.
start another timer
second (phase shifted) signal's leading edge arrives - stop the other timer.



here's the bit I'm using for frequency detection (for clarity I've ommited the config/registers as this bit works)...

INCLUDE "DT_INTS-14.bas"     ' Base Interrupt System  PO90OOO9
INCLUDE "ReEnterPBP.bas"     ' Include if using PBP interrupts

ASM
INT_LIST  macro    ; IntSource,        Label,  Type, ResetFlag?
        INT_Handler   CMP2_INT,  _Comp2_Int,   PBP,  yes
    endm
    INT_CREATE               ; Creates the interrupt processor
ENDASM

@ INT_ENABLE  CMP1_INT     ; enable Comparator 1 interrupts
@ INT_ENABLE  CMP2_INT     ; enable Comparator 1 interrupts

Comp1Time = 0 'clear down Comp1Time, prior to starting.
comp2Time = 0  'clear down Comp2Time, prior to starting

'Main body of Code*********************************************************************************************
Main:

        HSEROUT ["comp2=", dec comp2Time,9,"comp1=", dec Comp1Time, 13, 10]
        goto Main
        end
   
'Comparator1 Interrupt Handler+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++        
Comp2_Int:
        if T1CON.0= 0 then 'if timer1 is not running then...
        TMR1H = 0 'Set the high part of the timer value to 0
        TMR1L = 0 'Set the low part of the timer value to 0 
        T1CON.0= 1  'start timer
        else        
        T1CON.0= 0  'stop timer1
        Comp2Time.Lowbyte = TMR1L            'puts the timer's low byte in Comp1Time's lower 8 bits 
        Comp2Time.Highbyte = TMR1H           'puts the timer's high byte in Comp1Time's upper 8 bits
        Comp2Time = Comp2Time
        endif
@ INT_RETURN

but when I add in a little bit extra (bolded below in red), the HSEROUT chokes....

@ INT_ENABLE  CMP1_INT     ; enable Comparator 1 interrupts
@ INT_ENABLE  CMP2_INT     ; enable Comparator 1 interrupts

Comp1Time = 0 'clear down Comp1Time, prior to starting.
comp2Time = 0  'clear down Comp2Time, prior to starting

'Main body of Code*********************************************************************************************
Main:

        HSEROUT ["comp2=", dec comp2Time,9,"comp1=", dec Comp1Time, 13, 10]
        goto Main
        end
   
'Comparator1 Interrupt Handler+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++        
Comp2_Int:
        if T1CON.0= 0 then 'if timer1 is not running then...
        TMR1H = 0 'Set the high part of the timer value to 0
        TMR1L = 0 'Set the low part of the timer value to 0 
        T1CON.0= 1  'start timer1
        else        
        T1CON.0= 0  'stop timer1
        TMR2 = 0 'clear tmr2
        T2CON.2 = 1  'start tmr2
        Comp2Time.Lowbyte = TMR1L            'puts the timer's low byte in Comp1Time's lower 8 bits 
        Comp2Time.Highbyte = TMR1H           'puts the timer's high byte in Comp1Time's upper 8 bits
        Comp2Time = Comp2Time
        endif
@ INT_RETURN

Comp1_Int:  ' store the amount of clock pulses elapsed since routine above finished
        T2CON.2 = 0
        COMP1TIME = TMR2
        TMR2= 0
@ INT_RETURN