Nrf52832 Internal ADC is taking approx 35us. Need help to minimize it withing 10us

RE: Nrf52832 Internal ADC is taking approx 35us. Need help to minimize it withing 10us

Jared — Mon, 12 Sep 2022 11:23:51 GMT

Hi there,

There isn't an API for increasing the buffer size, instead you would have to increase the size of the nrf_saadc_value_t array buffer that you pass to nrf_drv_saadc_buffer_convert(). Increasing the buffer size means that nrf_drv_saadc_buffer_convert() which process the sampled data has to be called less often as it takes longer time for the buffer to fill with sampled data.

If you use PPI + SAADC as in the SAADC example in the SDK then sampling is done automatically on a COMPARE event as long as the SAADC START task has been triggered( which is done automatically in nrf_drv_saadc_buffer_convert())

regards
Jared

RE: Nrf52832 Internal ADC is taking approx 35us. Need help to minimize it withing 10us

SanketSkyline — Fri, 09 Sep 2022 14:24:24 GMT

Hello Jared,

As per your reply "you can decrease the amount of time that you need to call the conversion routine by increasing the buffer size and only processing the data when you need to. "

Would you please help to share the API which will do these steps as you mentioned?

Also, let me know if nrfx_saadc_sample_convert() does not start the sampling then which API shall I use to start the sampling whenever it is desired ?

Best Regards,

Sanket Chadawar

RE: Nrf52832 Internal ADC is taking approx 35us. Need help to minimize it withing 10us

Jared — Fri, 09 Sep 2022 09:04:24 GMT

Hi Sanket,

nrfx_saadc_sample_convert() does not start the sampling, it will instead process the already sampled data from the buffer. Decreasing the acquisition time will therefore not affect the conversion time. I don't think it's possible to change the conversion time. However, you can decrease the amount of time that you need to call the conversion routine by increasing the buffer size and only process the data when you need to.

regards

Jared

RE: Nrf52832 Internal ADC is taking approx 35us. Need help to minimize it withing 10us

SanketSkyline — Fri, 09 Sep 2022 04:30:55 GMT

Hello Jared,

"I don't think there is any way of decreasing this time actually. Are you trying to decrease the SAADC sampling time? "

The API nrfx_saadc_sample_convert() is taking approx 35us to give one ADC sample. I want to minimize this time period so that is why I tried changing the acquisition time but as per your reply, it seems that that will not optimize the time.

Is it possible in any way to reduce the time period required by nrfx_saadc_sample_convert() ?

Best Regards,

Sanket Chadawar

RE: Nrf52832 Internal ADC is taking approx 35us. Need help to minimize it withing 10us

Jared — Thu, 08 Sep 2022 14:03:11 GMT

Hi there,

Decreasing the acquisition time wouldn't affect the time it would take the CPU to retrieve the already sampled values from the EasyDMA buffers. I don't think there is any way of decreasing this time actually. Are you trying to decrease the SAADC sampling time?

regards

Jared