gnupic: Pic A/d Weirdness.
Subject:
Re: Pic A/d Weirdness.
From:
Declan Moriarty ####@####.####
Date:
11 Nov 2002 17:38:38 -0000
Message-Id: <02111117132601.00832@genius.chateau.dec>
Was it Rogier Wolff who wrote on Monday 11 November 2002 11:17:
> On Sat, Nov 09, 2002 at 07:13:01PM -0800, Scott Dattalo wrote:
> > On Sat, 9 Nov 2002, Declan Moriarty wrote:
> > > I have a little pic project goine here - e v e n t u a l l y!
> > >
> > > The one fly in the ointment is a temprature routine, in which my A/D
> > > doesn't make sense, but returns a value of 3ff for the 10 bits :-(
> >
> > Try replacing the temperature transducer with a voltage source that can
> > be varied. The best "voltage source" in your case may be a potentiometer.
> > If you connect the two ends of the pot to Vref- and Vref+ and connect the
> > wiper to your analog input, then you should be able to turn the knob on
> > the pot and cover the full analog range. I'm not suggesting that this
> > will fix your problem, but it can remove one of the unknowns.
>
> Another thing I've done in the past is to measure the voltage on the
> analog input to hand-calculate the expected AD conversion value.
>
> Especially once it starts falling in range it is a good sanity check.
Thanks for your replies.
Nobody's telling me I'm doing something stupid with my code, and nobody says
the PIC won't live with a -vref of +1.5V. These for me were the essential
sanity checks. As for the hardware, the voltage is between -vref and +vref
which is where I hoped it would be. It could even be a pcb error.
I decided the temprature was 22 degrees celcius, and hacked the software
accordingly :-D. The first model has gone out, and the pressure is off me
now. Now I can run through things a little more slowly, and I will certainly
try all of what has been suggested.
--
Regards,
Declan Moriarty
Applied Researches - Ireland's Foremost Electronic Hardware Genius
A Slightly Serious(TM) Company
Without the optimist, the pessimist wouldn't know how happy he isn't
