Calibrating SAADC on nRF52

[Hamid]

I have to sample 3 differential channels periodically. Should I calibrate SAADC for each channel individually? Unfortunately, "nRF52832 - Product Specification v1.0" doesn't explain the process in details! Would you please explain the mechanism of SAADC calibration in more details?

Thanks.

[Jørgen Holmefjord]

Hi,

It is recommended to run offset calibration periodically to compensate for temperature drift. Calibration can be started by calling nrf_drv_saadc_calibrate_offset() if you use the SAADC driver. It is not possible to select channel for this task, just make sure to run it either periodically or whenever there is change in temperature.

If you want to make the SAADC output more stable, you could enable oversampling, or connect a capacitor to reduce noise, as described in this blog post. An example showing both oversampling and offset calibration can be found on our GitHub page.

Best regards,

Jørgen

[MJ Ma]

Ho Jorgen I cannot find nrf_drv_saadc_calibrate_offset() in the SDK 11, would you please help tell me why

[Jørgen Holmefjord]

Hi MJ Ma, I see that the function was first introduced in SDK 12.x. If you want this function, you can copy it from SDK 12 to SDK 11. Notice that there is also a new state introduced: NRF_SAADC_STATE_CALIBRATION, which you might have to implement as well to get correct functionality.