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Is there a rule on pin pairs for sigma-delta A/D use? — Parallax Forums

Is there a rule on pin pairs for sigma-delta A/D use?

HarleyHarley Posts: 997
edited 2010-07-14 03:33 in Propeller 1
If I recall there was some discussion maybe 2-3 years ago about this subject. But it was so far beyond my understanding of the Prop (I didn't even know about AN001then) at that time.

I'm using Rayman's PTP LCD board and from his schematic there happens to be 6 free I/O pins, P4..P9. I need a 4-bit D/A leaving me just 2 pins, enough for the A/D. My question is this, which two of those 6 pins is the best for the A/D use? (For the D/A using the lower or upper 4 of the 6 pins is no problem; but prefer not to split them.)

Has there been any details on how to determine such a selection? (my first choice is the D/A gets the lower 4 and A/D upper 2.) yeah.gif

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Harley Shanko

Comments

  • Phil Pilgrim (PhiPi)Phil Pilgrim (PhiPi) Posts: 23,514
    edited 2010-07-14 03:01
    There have been some remarks about not using adjacent pins, due to capacitive coupling. I routinely use adjacent pins, however, and have not experienced any issues from doing so.

    -Phil
  • HarleyHarley Posts: 997
    edited 2010-07-14 03:33
    Phil said...

    There have been some remarks about not using adjacent pins, due to capacitive coupling. I routinely use adjacent pins, however, and have not experienced any issues from doing so.

    Sounds good that you've not encountered any problems using adjacent pins. Thanks so much. I'm fortunate that the PTP board only left just enough spare I/Os. And is surprising how nice the 3.5" color touchscreen LCD appear both off (very trim packaging) and in use.

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    Harley Shanko
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