gnupic: Re: [gnupic] help - weird intermittent resets
Subject:
Re: [gnupic] help - weird intermittent resets
From:
Dan Andersson ####@####.####
Date:
30 Jul 2005 09:07:00 +0100
Message-Id: <1122710816.8260.12.camel@hecate.andersson.co.uk>
As my old teacher in electronics always said...
Have you measured the circuit?
No, not with a DVM! With an oscilloscope!
You cannot claim a rock solid 4.85V from the supply until you measured
it with an oscilloscope.
Cheers
Dan
On Sat, 2005-07-30 at 14:13 +1200, David McNab wrote:
> Hi,
>
> I'm getting a weird and frustrating problem with a pic18f252 that
> intermittently resets itself.
>
> I've reduced my test program to the bare essentials - pseudo-code is:
>
> - clear trisc.0
> - while true
> - reset portc.0 # turn on piezo buzzer
> - wait 1ms # long enough to click buzzer
> - set portc.0 # turn off buzzer
> - wait 249ms
>
> Config:
> - wdt and bor are on
> - 20 MHz crystal, with 18pF caps to ground
>
> Observations:
> - pic resets at random times, varying between 1s and 20s
> - pic resets much less often when I disconnect the
> max232-based tty interface
> - pic resets less often with much smaller progs (eg, the above
> test prog written in c and compiled under ccs, as opposed to written
> in forth and bloated out to 4k by the vm and support code)
> - power supply is delivering rock-solid 4.85 volts
> - i cannot reproduce this resetting when running the prog via gpsim
>
> Thoughts:
> - crystal is dodgy, locking up
> - pic is affected by ambient electrical noise
>
> Any ideas on cause, and fix/workaround?
>
