Please help me understand this code

[lilimike]

Hi,
From the code bellow, I am expecting to have the DEBUG line running only when the variable "ReadFlag" is set and it does, so far so good.
But once it ran, I clear ReadFlag and it should become set again ONLY if I=10 and this should happen only after the Interrupt has ran 10 times right? Well it is not happening.

In my DEBUG line "I" shows up as 0,2,4,5 randomly
I am not using variable "I" anywhere else other than:

I VAR BYTE
I = 0

at the top of my program.


Can someone help me understand this?

Goto main 
    
Main:
    DO while readflag = 1 
        debug dec Fvalue," i=",dec i," R=",dec readflag,10,13  ; Display on terminal if ReadFlag = 1
        readflag = 0            ; do not update until the next 10 readings
        Fvalue = 0
    LOOP
goto main

'---[INT - interrupt handler]------Signal found at RB0, take a reading
SignalFound:
    T1CON.0 = 0                             ; Stop timer1
    i = i + 1                               
    FValue = TMR1H * 256 + TMR1L + fvalue   ; Add 10 readings to FValue
    if i = 10 then
        fvalue = fvalue / 10                ; get the average of one reading
        i = 0                               ; Reset counter
        ReadFlag = 1                        ; FValue is ready to read 
    endif        
    TMR1H = 21                              ; reset timer1 to 60mS
    TMR1L = 167
    T1CON.0 = 1                             ; Start timer1
@ INT_RETURN

Thanks

Mike

[lilimike]

Getting even more confusing, I tried:

DO while I = 0

And still the DEBUG line shows up even when: I > 0

[Bruce]

In my DEBUG line "I" shows up as 0,2,4,5 randomly

You probably have several timer interrupts while it's inside your DO LOOP, so I ends up with unexpected values.

Example: With i = i + 1 being first in your timer interupt, it's changing the value of i on every interrupt, and sometimes even during the process of PBP trying to output everything with DEBUG.

When DEBUG actually starts, your interrupt is still changing I before PBP outputs it.

[Jerson]

Try this. Changes are in Bold

'---[INT - interrupt handler]------Signal found at RB0, take a reading
SignalFound:
    T1CON.0 = 0                             ; Stop timer1
    i = i + 1                               
    FValue = TMR1H * 256 + TMR1L + fvalue   ; Add 10 readings to FValue
    if i >= 10 then                        ' COMPARISON CHANGED TO >=
        fvalue = fvalue / i                ; get the average of one reading CHANGED HERE
        i = 0                               ; Reset counter
        ReadFlag = 1                        ; FValue is ready to read 
    endif        
    TMR1H = 21                              ; reset timer1 to 60mS
    TMR1L = 167
    T1CON.0 = 1                             ; Start timer1
@ INT_RETURN

[lilimike]

Hi Bruce and Jersen,

That is really fast !

Jerson,
I was able to observe the proper values by moving the DEBUG line inside the INT handler.

Is there a more efficient way to observe variables values within a program?
It seams like LCDOUT and DEBUG are taking too long to operate and are giving false values.

Thank you

Mike

[lilimike]

Bruce,

I came across this link you wrote Entitled "Using MicroCode Studio ICD
With The PIC16F628 Microcontroller" http://www.rentron.com/PicBasic/MCS_X3.htm
Would this enable me to view each step of a program as well as where the PIC timer is at while executing a specific line of code?

Mike