How to connect 8 mems microphones to DFSM using 4 filters?

[RTolm.1]

Hello! I am using a stm32f765 chip. I need to connect 8 microphones to the DFSDM, but there are only 4 filters in the chip and I cannot use the regular read mode from all 8 channels of the DFSDM. I found information that the dfsdm filter allows to read values in an injection mode from several channels, but in this case the frequency and quality of the audio drops and this method is not suitable for audio. Also, I did not find examples of how to implement 8 microphones and 4 filters. Please let me how to use the 8 microphones with 4 filters for audio, or, please, give the example.

Thanks for any answer!

[waclawek.jan]

Well, as you've already found out, you simply can't.

You may consider adding a second mcu with DFSDM, handling the remaining 4 channels. You can also try to filter 4 channels purely in software, I am not sure whether this is feasible, it's upon you to implement it and try.

JW