ADC MUX Scan Mode Question - will it permute all combinations?

[the_reza]

For the nRF5xxxxx series, it looks like it has a differential ADC with 8 positive and 8 negative channels.  It also looks like it has a scan mode where it will sequentially scan all the channels and sample them.   What's not clear is if I have all 8 positive and 8 negative channels enabled, will scan mode sample all 8x8=64 permutations of channels selected, or only scan the positive and negative corresponding channel numbers (8)?  

For my application, I'm interested in sampling all 64 combinations of positive and negative channels with a 1khz sampling rate per channel.  If the hardware doesn't support this type of scanning, can I achieve this using some other means?

[Jørgen Holmefjord]

Hi,

The nRF52/nRF53 SAADC peripheral have 8 channels, there are not separate positive and negative channels. Each channel can set one positive and one negative input. The chips only have 8 analog inputs pins, which means you can have either 8 positive inputs, 8 negative inputs, or a mix of 8 positive and negative inputs.

Scan mode will sequentially sample the enabled channels, maximum 8 channels. It is possible to reconfigure the inputs in order to sample more combinations of positive and negative inputs, but this needs to happen after the scan cycle, meaning you will need to trigger a new sample for the updated inputs. This will reduce the achievable sample rate. You will anyways be limited to 8 inputs, or 4x4=16 permutations.

Best regards,
Jørgen