Interrupts and WDT are driving me nuts!

I am adding a feature to an existing device (I know, I know, leave well enough alone).

Essentially, when one of the switches is on (logic low), I want an LED on steady. When the switch is off, I want the LED to be on for 1/4 second out of two - in other word, off for 1.75 seconds.

To accomplish this I planned on a sleep (already in the program - the existing wakes up only on change of state for PORTB.0) and have it wake up every 250 (or so) milliseconds, go to the interrupt handler and, based on a counter, turn the LED on or off.

I have used interrupts when I programmed in assembler but never in PBP.

I have tried several versions of this, and have even pared the program down to JUST doing the above - but no matter what I do, it doesn't function properly - the blinking doesn't happen, but the switch DOES turn on the LED as long as its held. Almost like the WDT is not running, or its not jumping to the interrupt handler.

BTW, its a 16F886.

Anyway, below is the listing. If anyone has any idea what I'm doing wrong, let me know - I'm tired of tearing my hair out. And this is PERSONAL now! :wink:

Code:

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#CONFIG
 __config _CONFIG1, _INTRC_OSC_NOCLKOUT & _WDT_ON & _MCLRE_OFF & _LVP_OFF & _CP_OFF

#ENDCONFIG

DEFINE OSC 8  'LETS PBP KNOW THE OSCILLATOR IS RUNNING AT 8MHz

OSCCON = %01110001 '8 MHz INTERNAL OSCILLATOR, INTERNAL OSCILLATOR IS USED FOR SYSTEM CLOCK

DISABLE DEBUG 'NO DEBUG

ANSEL = 0 'PORTA ALL DIGITAL
ANSELH = 0 'PORTB ALL DIGITAL

OPTION_REG = %10000000 'PORT B PULLUPS ENABLED, TMR0 PRESCALER IS *NOT* ASSIGNED TO WDT
WPUB = %01111111 'PULL UPS ENABLED ON PORTB 0-6

INTCON = %10001000 'GIE ENABLED, PORTB CHANGE OF STATE INTERRUPT ENABLED
IOCB = %00000001 'PORTB.0 INTERRUPT ON CHANGE ENABLED
WDTCON = %00010000 '1:8192 PRESCALER (272MS)

TRISA = 0 'PORTA ALL OUTPUTS
TRISB = %01111111 'B7 OUTPUT, ALL THE OTHERS INPUTS
TRISC = 0 'PORTC ALL OUTPUTS

SWITCH VAR PORTB.0
LED VAR PORTC.6

DEBOUNCE VAR BYTE
DUMMY VAR BYTE
BLINK_COUNT VAR BYTE

DEBOUNCE = 30 'MILLISECONDS

ON INTERRUPT GOTO MY_INT
BLINK_COUNT = 0
MAIN_LOOP:
        DO 'ENDLESS LOOP
                        IF SWITCH = 0 THEN 'SWITCH ON
                        PAUSE DEBOUNCE 'DELAY TO DEBOUNCE
                                IF SWITCH = 0 THEN 'SWITCH STILL ON
DISABLE INTERRUPT
                                        LED = 1 'TURN LED ON STEADY WHILE SWITCH IS OPERATED
                                        DO WHILE SWITCH = 0
                                        LOOP
                                        PAUSE DEBOUNCE
                                        LED = 0 'TURN OFF THE LED TO ALLOW THE INTERRUPT HANDLER TO BLINK IT
                                        BLINK_COUNT = 0
                                        GOTO DONE_LOOP
                                ENDIF
                        ENDIF
DONE_LOOP:
                INTCON = %10001000 'TURN ON GIE AND INTERRUPTS FOR PORTB.0 CHANGE OF STATE AND CLEAR FLAGS
                WDTCON = %00010000 '1:8192 PRESCALER - 272MS (CLRWDT RESETS THIS TO 17MS)
ENABLE INTERRUPT                                       
                ASM
                        SLEEP        'SLEEP UNTIL WDT TIMES OUT OR PORTB.0 CHANGES STATE
                        NOP                'NOP BECAUSE THE PROCESSOR PREFETCHES PC+1 ON SLEEP
                ENDASM

        LOOP
       
DISABLE 'DISABLE INTERRUPTS BELOW THIS POINT
MY_INT:
        DUMMY = PORTB 'READ PORTB TO CLEAR THE SWITCH MISMATCH IF THAT GENERATED THE INTERRUPT
        IF BLINK_COUNT = 8 THEN BLINK_COUNT = 0
        IF STATUS.4 = 0 THEN 'WDT TIME OUT OCCURRED
                BLINK_COUNT = BLINK_COUNT + 1
                IF BLINK_COUNT > 1 THEN
                        LED = 0
                ELSE
                        LED = 1
                ENDIF
        ENDIF
        INTCON = %10001000 'TURN ON GIE AND INTERRUPT PORTB.0 CHANGE OF STATE, AND CLEAR FLAGS       
        WDTCON = %00010000 '1:8192 PRESCALER - 272MS (CLRWDT RESETS THIS TO 17MS)
        RESUME  'IF NO WDT TIME-OUT OCCURRED, THEN THE SWITCH WAS TURNED ON NO NEED TO DO ANYTHING
                        'AS THE SWITCH WILL BE CAUGHT BY THE MAIN LOOP               
               
END

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