nRF52840 Low Frequency Noise Sources

Question

Hi, 
 I am using an Adafruit nRF52840 Express with a sensor board attached to it. I'm noticing that my sensor IC is reading about 3-6dB higher noise in the 10-50Hz range (and likely higher) when the Bluefruit BLE stack is running from Adafruit which is based on the s140 6.1.1 softdevice. I have been unable to dig into the BLE subsystem so far and find the possible noise source. 
 Would you have a suggestion as to where in the softdevice I should focus on to review possible noise sources? 
 Best, Matt

Carl Richard · Accepted Answer

Hello again! I got back from the developers that it shouldn't be possible to use two different clocks sources. But the LFCLK is configured twice by Adafruit, so it may be that you end up using LFRC for the whole device. We suspect that it may be something HW related that causes this. Have you tested the other sensors/connecting the sensor directly to see if the noise is present/different then? Hopefully the people at Adafruit will give some more insight too. Your clock_cfg should be adequate. PS: suggested your previous post as an answer. Did not mean to do this, so it can be ignored! Best regards, Carl Richard

nRF52840 Low Frequency Noise Sources

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