nRF52832 SAADC 14-bit with 0 oversampling

RE: nRF52832 SAADC 14-bit with 0 oversampling

nrfcho — Mon, 03 Aug 2020 02:16:37 GMT

HI, also I want to get 11bit resolution..Could you tell me how you made your own oversampling? Thanks

RE: nRF52832 SAADC 14-bit with 0 oversampling

Podrucky — Fri, 06 Sep 2019 16:12:13 GMT

I understand Sean. Thank you for the information. I had some recent success with achieving actual 11 bit resolution using a 12 bit resolution, using VDD/4 as the reference and disabling the DC/DC on the nrf52832. I require an ADC value every 100 ms so I performed my own oversampling and average, taking 50 readings during the 100 ms timeframe. I did not disable the soft devices during sampling and this method may yield more accurate results to eliminate systematic noise.

RE: nRF52832 SAADC 14-bit with 0 oversampling

SeanK — Thu, 05 Sep 2019 00:21:09 GMT

I have the answer to my own question.

14-bit format is just that - a format. If oversampling is Disabled in sdk_config.h, there is no oversampling performed. Selecting SAADC_CONFIG_RESOLUTION 3 gives you a 14-bit format, but it's 12-bit ADC data multiplied by 4.

I used the PCA10040 to take the following data. For brevity i've only shown the first 20 samples. Results are in counts.

The following are some calculations on 100 samples (of which the first 20 samples are included above). Results are in ADC counts.

RE: nRF52832 SAADC 14-bit with 0 oversampling

SeanK — Thu, 05 Sep 2019 00:04:10 GMT

The saadc example provided in the SDK is a good place to start to get ADC measurements working on the dev board. Edit the file sdk_config.h; Changing SAADC_CONFIG_RESOLUTION to 3 will achieve 14 bit responses

// <o> SAADC_CONFIG_RESOLUTION  - Resolution
 
// <0=> 8 bit 
// <1=> 10 bit 
// <2=> 12 bit 
// <3=> 14 bit 

#ifndef SAADC_CONFIG_RESOLUTION
#define SAADC_CONFIG_RESOLUTION 3
#endif

RE: nRF52832 SAADC 14-bit with 0 oversampling

Podrucky — Wed, 04 Sep 2019 20:42:34 GMT

I am wondering how to get 14 bit ADC measurement working. Could you post your code?