Hello,
I am trying out a SAM7S256-EK and have been working through the example programs. I am having trouble with the basic-adc-project. When running (SRAM), the input pins for some of the ADC pins are driven high (~2.2 V). I tried applying a voltage to it with a FLUKE 725, but even that cannot over power the voltage present. So what is going on? I initialized the ADC, enabled the select channels, read CHSR to check even, started converstion, waited for it to finish, got the data and converted it to voltage. What did I miss?

I am running with GNU so I used the new software examples rather than the ones that came on the CD. It was packaged in 2005 so it didn't have the GNU examples on it.

Thanks for the help.

From the datasheet:

AD0-AD3 Digital pulled-up inputs at reset

Must be some sort of register setting that turns off the pull up.

Thanks falingtrea, you are right on both accounts (as far as I know), but...

You can disable the pull-ups with the PIO_PPUDR register and check them with PIO_PPUSR. However, I think that if you enable the ADC channels (AD0-AD3) this is done four you in the "ADC_EnableChannel" somewhere.
I checked this using this code:
printf("PIOA_PUSR : 0x%X\n\r", AT91C_BASE_PIOA->PIO_PPUSR);

Also, since the dedicated ADC channels AD4-AD7 are not multiplexed there would be no reason to have them pulled up (nor can you access them to disable a pull up setting in PIO_PPUDR anyway). So, why the 2v on the line?

Any other ideas?