On Thursday 28 November 2002 13:18, you wrote: > Hey Declan, > That sounds about right. I was about to e-mail you and ask about this. > There is an app note on the A/D converter that indicate that if (1) the > Vref is not up to Vdd and/or Vdd is not at least +5V your measurements will > be unstable. Another thing to keep in mind is the TAQ and THOLD times. If > they are not set long enough, the internal acquisition ckt will not > function correctly either, yielding in varying results (the internal cap > must have time to charge and then dissipate). I'm not sure you covered this > in your original e-mail. Anyway, check out AN546. It covers the general > operation of the A/D. Jay
Thanks for the ideas. In actual fact, I have converted to a 5V reference voltage. I rewrote the assembler today to read channel 2, read channel 0, subtract channel 2 from channel 0, and resolve. I'm coming out a degree or two up but they don't care. It is repeatable and accepts minor changes, which ios the important thing. It makes the battery voltages a little more critical, but there's a couple of volts headroom there anyhow. So the last thing I want to do now is read another app note ;-) In future models I can probably fiddle the hardware for an improvement onb quality in this area. -- Regards, Declan Moriarty. -- Author: Declan Moriarty INET: [EMAIL PROTECTED] Fat City Network Services -- 858-538-5051 http://www.fatcity.com San Diego, California -- Mailing list and web hosting services --------------------------------------------------------------------- To REMOVE yourself from this mailing list, send an E-Mail message to: [EMAIL PROTECTED] (note EXACT spelling of 'ListGuru') and in the message BODY, include a line containing: UNSUB CHIPDIR-L (or the name of mailing list you want to be removed from). You may also send the HELP command for other information (like subscribing).
