SAADC oversampling sampling interval?

RE: SAADC oversampling sampling interval?

Jørgen Holmefjord — Tue, 11 May 2021 07:23:41 GMT

The sample time depends on the configured acquisition time, which can be set between 3 and 40 us. The minimal delay between two samples needs to be t_ACQ+t_CONV. t_CONV is given in the product specification, and is maximum 2 us.

How to setup the sampling depends on your configuration and what source you use to trigger the sampling. If you want to capture 6 samples in 30 ms with 8x oversampling, the simplest solution would be to enable BURST and trigger the sample task every 5ms. Even with maximum acquisition time, you will not get near 5ms: (40us + 2us) * 2^3 = 42us * 8 = 336us.

RE: SAADC oversampling sampling interval?

Tajpeer — Tue, 11 May 2021 06:22:19 GMT

Hi Jorgen,

Thanks for the information.

But still I am not clear how to configure the sample time for each sample manually.

My requirement is to sample 6 samples in a period of 30ms using oversampling.

RE: SAADC oversampling sampling interval?

Jørgen Holmefjord — Mon, 10 May 2021 11:25:28 GMT

Hi,

I would recommend you to enable BURST when oversampling is enabled, as described in the Oversampling chapter in the SAADC peripheral documentation. Then you only need to trigger the SAMPLE task once to get all samples required by oversampling to generate one result.

The timing will depend on the configured acquisition time, <(t_ACQ+t_CONV)×2^OVERSAMPLE . If you want to sample manually, the time between each SAMPLE needs to be at least t_ACQ+t_CONV.

Burst is enabled in the channel config structure if you are using the SAADC driver.

Best regards,
Jørgen