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Strange goings on with pic32mx274 a2d.

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nigelwright7557
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2020/06/02 18:53:11 (permalink)
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Strange goings on with pic32mx274 a2d.

Been working on a transistor curve tracer using PWM outputs to generate voltages and 2 A2D channels to read in outputs from transistor.
The NPN transistor channel worked a treat but the PNP channel was about 2 volts off on the transistor output.
Spent a good hour tracing problems but couldnt find any until  I looked at A2D input for that channel and the volts were wrong.
It seems my PICKIT3 was interfering with the A2D input on A2D channel 2.
I disconnected it and all was ok.
That a2d input is also a programming pin. I have put a resistor in series with it so I could still program the device while getting analogue data in.
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    ric
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    Re: Strange goings on with pic32mx274 a2d. 2020/06/02 19:15:20 (permalink)
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    The PK3 has permanent 4.7k pulldowns on PGD and PGC.
    You must disconnect it if you want to use that pin for something else after programming.
     

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    nigelwright7557
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    Re: Strange goings on with pic32mx274 a2d. 2020/06/02 19:23:08 (permalink)
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    ric
    The PK3 has permanent 4.7k pulldowns on PGD and PGC.
    You must disconnect it if you want to use that pin for something else after programming.

    I didnt know that.  I could have used AN4 or AN5 instead.
    My Snap programmer does the same.
    #3
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