SAADC sample doesn't appear to be working

RE: SAADC sample doesn't appear to be working

Mike Austin (LPI) — Wed, 24 Jul 2024 02:59:57 GMT

The loopback pin just connects the output of a GPIO to the input of one of the ADC inputs. Then, the code is toggling the state of the GPIO pin, so that in between successive reads of the ADC pin, you should see the result go from ~ 0V to ~ 3V. You can skip the loopback pin connection altogther, and just connect a variable DC voltage up to the ADC input pin and you should see the result vary as you change the input level

Note that I have found in V2.6.0 when running any of hte nrfx_saadc examples, that the call to the saadc calibrate API never seems to return, which means the nrfx_saadc_mode_trigger() API doesn't get triggered, and no ADC measurements are made.

I have this ticket open regarding this issue, and Nordic have been able to replicate it

Cheers,

Mike

RE: SAADC sample doesn't appear to be working

Naeem Maroof — Mon, 22 Jul 2024 16:22:18 GMT

Hi,

The two pins are the P (VP) and N (VN) pins for the SAADC:

and the SAADC calculates the digital output as:

RE: SAADC sample doesn't appear to be working

finkbr — Sun, 21 Jul 2024 16:31:28 GMT

After a bunch more playing around, I was able to get the example to work. If you could just answer the last bit about what the loopack pins are doing so I can understand what's going on I'd appreciate it. I need to make tis example work on my custom board next. Then you can close this ticket.