How does the SAADC "Scan" mode use the "BURST=1"

RE: How does the SAADC "Scan" mode use the "BURST=1"

snoopy20 — Fri, 19 May 2023 20:22:28 GMT

For anyone that comes on to this, it's not documented but for burst+scan to work you must use the same TACQ for all channels otherwise it's garbage out.

RE: How does the SAADC "Scan" mode use the "BURST=1"

Alessandro — Thu, 30 Mar 2017 12:08:01 GMT

Thanks for spotting this. On sdk 12.2 I am able to enable scan mode and burst mode without modifying the driver. It seems it's working fine so far.

RE: How does the SAADC "Scan" mode use the "BURST=1"

Dale — Sat, 18 Mar 2017 00:40:04 GMT

Carsten, thanks for your answer it confirmed what I thought. I did modify the driver (made a local copy) to be able to set up the Oversample with Scan (multiple channels enabled) and the burst enabled. It does appear to work correctly.

Improvement should be made to the documentation to make this more clear and the "nrf_drv_saadc" driver needs to be updated in the SDK to support this ability, it is a rather nice feature!

RE: How does the SAADC "Scan" mode use the "BURST=1"

Carsten Wulff — Fri, 17 Mar 2017 18:58:56 GMT

The short answer is yes, burst with oversample does averaging.

Assume the following scenario; Scan is enabled on two channels, and oversample is set to 1. In that case the output will actually be dout[n] = (ch0[n] + ch1[n])/2, which is most times unwanted. However, if you enable BURST it will take 2^oversample samples per channel, and average those. Thus, dout0[n] = (ch0[n]+ ch0[n+TACQ+TCONV])/2 and the same for channel two.