how to set pin pull-down

[fomm]

i'm trying to read voltage signals from a sensor using internal ADC.When the input is not connected,there will be noise.
I use differential input pins like this:

NRF_DRV_SAADC_DEFAULT_CHANNEL_CONFIG_DIFFERENTIAL(NRF_SAADC_INPUT_AIN1,NRF_SAADC_INPUT_AIN0);

So I want to know how to pulldown pin enabled as an ADC input at the code level?

[Hieu]

Hi fomm,

Note how NRF_DRV_SAADC_DEFAULT_CHANNEL_CONFIG_DIFFERENTIAL is just an alias of NRFX_SAADC_DEFAULT_CHANNEL_CONFIG_DIFFERENTIAL. You will see that the macro is just a helper to set your nrf_saadc_channel_config_t structure.

The pull-down resistor is controlled by the resistor_n field of that structure. To set the resistor_n You can either set the nrf_saadc_channel_config_t structure on your own without the helper, or just set it later to your desired configuration.

The way you can figure this out is to note from the SAADC peripheral documentation that this feature is done by a pull-down resistor, enabled by the RESN bit in CH[n].CONFIG. You can then look up the keywords "resistor" or "pull" in the driver documentation or header files.

Hieu