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Hot!External Vref on PIC32MX570F512L

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2020/12/01 12:26:40 (permalink)
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External Vref on PIC32MX570F512L

Using PIC32MX570F512L on a new project. We ended up needing to use an external 2.5V A/D reference. Even though I set the TRISA bits for RA9 and RA10 port pins to make them inputs, the Vref+ pin was driving high until I set the ODCA bits for these pins. Has anyone else encountered this? It doesn't make much sense.
 
Dave
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    ric
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    Re: External Vref on PIC32MX570F512L 2020/12/01 12:35:56 (permalink)
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    Can you check in the debugger to make sure the TRIS bits are still set after initialisation?
    The most likely explanation is a software bug.
     

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    Re: External Vref on PIC32MX570F512L 2020/12/01 12:41:27 (permalink)
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    I don't use the debugger much, but I could probably do a read on the TRISA register and spit it out of the serial port. I won't be able to do that until the hardware guy is done checking out the new prototypes and gets me some hardware to play with. Right now I've been adjusting the code and sending it to him (I'm still working remote from home these days).
     
    Dave
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    Re: External Vref on PIC32MX570F512L 2020/12/02 19:36:00 (permalink)
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    Just noticed that the latest errata for this family has some additional items including #17, which indicates that under some circumstances I/O pins "can be in an active random output driving state if MCLR is active until a BOR event". One work around involves removing the 0.1 uF cap to ground, which our device still has. I wonder if this could be the issue. Until this latest round of boards, we were not using any port A pins.
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