ADC problems on P0_0

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1

I have an input connected to P0_0. I’ve confirmed the connection.
But I can’t seem to get the input voltage to show up on P0_0. Either with the adc or a multimeter.

P0_1 works fine.

Is there anything special about P0_0. Maybe I’m not disabling the pull-up/pull-downs properly. I have P0INP = 0x3F;

How do you disable the pull-up/pull-downs on a single pin? A pointer to the right doc would help.

Thanks a lot,
Colin

2

Hello, Colin.

The Wixel’s ADC functions are documented here:

pololu.github.io/wixel-sdk/adc_8h.html

The documentation of the pull-ups and pull-downs can be found in the CC2511 datasheet, or you could just use the Wixel’s gpio library to configure those:

pololu.github.io/wixel-sdk/gpio_8h.html

In general, you can find Wixel library documentation by going to the Wixel SDK Documentation, then clicking on the “Libraries” link on that page.

You should be able to just call adcRead(0) to read P0_0, assuming that you have not configured that pin as an output. Your value for P0INP looks fine.

The Wixel’s ADC just measures the voltage on the input line. If you are unable to get that voltage to change to the desired level, then the ADC will not give you the desired reading. You should focus on getting the voltage (as measured by your multimeter) to change to the desired level. Since it is not at the desired level, you might have accidentally configured P0_0 as an output or there might be something wrong with other components in your setup.

–David

3

Thanks David. You don’t suppose it could have been something to do this, do you?

setDigitalOutput(param_arduino_DTR_pin, LOW);

Colin

4

If param_arduino_DTR_pin is 0 in your app, then that would certainly explain the problem you are seeing. --David