Software PWM lockup on a 16F877A

[comwarrior]

Call me a Muppet and stripe me pink!

I could have sworn they were gosubs! Honestly... i seen gosubs...
Well spotted!

I'll re-program in the morning...

[comwarrior]

ok... getting annoyed!
Changed the goto's to gosubs... same fault...
Disabled BOTH interupts so that all it has to do is flash an LED using pauses... same fault...
I've disabled the watchdog, power on timer, brownout reset and LVP and it still does it...

i'm seriously lost now... Help needed

[comwarrior]

Just for the hell of it... I tried another PIC same model and it does it on that too...

Any help is VERY appreciated

[comwarrior]

You are not going to believe this!

i tried a test program, disabled analog, turns all ports to output, sets all ports to low and then enters the same loop to toggle the LED... SIMPLE!
It failed and locked up...

so i asked myself, what is the diference between the 3mm red LED on PORTB.7 and the one on PORTD.0? so i switched them over... same result...

Just for the hell of it, i switched the resisters over and tried it... and it works!
I switched the resisters back and it locks up...

I took the suspect resister out and stuck it on my multimeter... it read less than 1ohm!
The resisters are supposed to be 68 ohms... this one is a faulty one...

So, the problem must have been caused by too much current through one of the IO lines...
I have lost 4 days trying to debug a problem caused by a 5 pence component that i would have never suspected if i was anywhere near sane!

So now i'm going to re-enable all my code and try it... god darn it!

[masosi]

Haha good to hear you found a problem!
I know that feeling too well, you're not alone!

[comwarrior]

it's absolutely ridiculous though!
I would have expected a supply of 5V to kill a 3.3V 3mm red led...
but no, the PIC just had to be clever...
Anyways, it's bed time...