18F2520 ADC issue

[Jerson]

Repeated failure after a fixed duration suggests stack problem to me. I can suggest you check the nesting levels in your code and if you have sufficient stack left over for interrupts use. Due to stack failure, the program could be returning to a wrong location and somehow modifying the CVRCON register and turning the AN2 port to output VREF. There may be other symptoms that accompany this.

[Acetronics2]

Hi, Jerson

as the AN2 input permanently stays "damaged" after some times ... I do not think it could be a stack or soft problem ...
as I wrote : re-programming the chip do not solve the issue ...

let's say the program continue to run pretty fine, of course excepting what relies to AN2 input ...

I must make some tests with RA2 as digital input/output ... just to try to see if something abnormal and verify if it is in the ADC input multiplexer or in the clamping diodes that the problem is ...

Alain

[Acetronics2]

Hi,

I finally found something ...

I used AN0 to AN2 ... and AN3 for external reference.

Innocently ... I had declared AN3 as analog in the ADCON1 register.

Looking closer to the Datasheet ... The reference DO NOT use the ADC multiplexer path.

So, I declared AN3 as digital ...

AND The right AN2 value re-appeared !!!



BUT that is because I do not use AN's inputs greater than 2 ... I would have to valid AN3 as Analog if using AN4 ...

So problem is still here.

I Just found a Turnaround ...

Alain