SAADC one-shot mode

RE: SAADC one-shot mode

Jørgen Holmefjord — Tue, 12 Jun 2018 07:37:33 GMT

That library configures the SAADC and perform single sample each time you call analogread function, which will cause a lot of overhead in CPU for other tasks than sampling. In order to achieve maximum sample frequency, the SAADC peripheral needs to be setup once, and sample task triggered from a timer through PPI channel, etc.

RE: SAADC one-shot mode

sasa-06 — Mon, 11 Jun 2018 21:13:20 GMT

Hi,

First, sorry for my english.

I recently bought the adafruit nrf52. I can read the voltage from analogread(). however the maximum sample frequency is 44kHz for one analoginput and 22 kHz if I want to read a second.
the configuration from the library is already with TACQ=3us.

link to the library GitHub

What do I need to make if I want to increase the frequency ?

Thanks

Best Regards!

RE: SAADC one-shot mode

SAM.MAO — Mon, 21 Aug 2017 08:51:32 GMT

Thank you anyway!

RE: SAADC one-shot mode

Jørgen Holmefjord — Mon, 21 Aug 2017 08:45:11 GMT

Hi Sam,

You can read about how to configure one-shot mode in the SAADC documentation.
The maximum sampling frequency depends on the configured aquisition time, which is configurable from 3-40 us. Sample time of 200 ns is not possible. With lowest aquisition time, the maximum sample frequency (f_SAMPLE) is 200 kHz:

f_SAMPLE = 1/(t_ACQ,10k + t_CONV) = 1/(3 us + 2 us) = 1/(5 us) = 200 kHz.

Best regards,

Jørgen