Example for using SAADC with NRF_SAADC_INPUT_VDDHDIV5?

[henris42]

Hello,

Is there example code on how to get NRF_SAADC_INPUT_VDDHDIV5 working? When I do nrfx_saadc_init(), I get NRF_ERROR_INVALID_STATE.

Same code works fine with normal ADC pins.

I'm using SDK 17.0.2, and the requirement is using pure nrfx directly. app_* functions etc are not available in this environment.

(Sorry I cannot share code. Its part of a big app so I cannot share anything compilable.)

[Karl Ylvisaker]

Hello, 

Is there example code on how to get NRF_SAADC_INPUT_VDDHDIV5 working? When I do nrfx_saadc_init(), I get NRF_ERROR_INVALID_STATE.

This is likely two different issues.
NRF_ERROR_INVALID_STATE is returned by nrfx_saadc_init when the driver is already initialized. You will only need to call this once, and it does not have anything to do with the channel PSELP. 

What unexpected behavior do you see when you configure a channel to measure on NRF_SAADC_INPUT_VDDHDIV5? Does your device reset, or does it generate an error?
Any information you could provide here would be helpful to better understand you issue and help debugging it.

Best regards,
Karl

[henris42]

OK, I did this and got the code move forward. 

However the reading kept so far solid number, not relevant to actual VDDH.

Is the nRF52840 revision relevant here?

[Karl Ylvisaker]

Please elaborate on what you are observing. The more details you provide the easier it will be for us to figure out and resolve your issue.

What is the solid number you are seeing? Are you printing the digital output of the SAADC directly, or are you doing some kind of conversion of the number in between?
If so, what functions have you made to perform these conversions? 
Also, the number will be VDDH/5, not VDDH directly.

Best regards,
Karl