FP-AUD-SMARTMIC1 package : How to acquire audio from a single microphone ?

[AAMAN.1]

Hi,

I'm currently using the FP-AUD-SMARTMIC1 package (https://www.st.com/en/embedded-software/fp-aud-smartmic1.html#:~:text=FP-AUD-SMARTMIC1%20is%20an%20STM32Cube%20function%20pack.%20This%20software,acquisition%2C%20beamforming%2C%20source%20localization%20and%20acoustic%20echo%20cancellation.) and doing some tests on the STM32F446RE board with 4 microphones on the CCA02M2 expansion board.

Usually, for 1 peripheral (I2S or SPI), the acquisition of 2 microphones is carried out on rising and falling edges of the microphones clock. I want to plug only 1 microphone recover the audio data of this microphone. My problem is that i don't understand why when only 1 microphone is plugged, I recover the audio data from the microphone which is connected but also from the second microphone which is not connected.

Thank you for your help.

Regards,

Annabel AMANS

[Eleon BORLINI]

Hi Annabel @AAMAN.1​ ,

>> Usually, for 1 peripheral (I2S or SPI), the acquisition of 2 microphones is carried out on rising and falling edges of the microphones clock.

That's correct. Usually, in a stereo configuration, the left mic is sampled on the falling clock edge while the right mic on the rising edge.

In case you have only 1 microphone on the line, and you acquire it in multichannel mode, you should see the same signal on both channels. In this case, you can simply ignore one of the two and use only the other one.

-Eleon