2 years, 9 months ago.

Using the microphone on the STM32L4 Discovery kit IoT node

I am trying to read in the data from the microphones (MP34DT01) on the STM32L4 dicovery node (DISCO-L475VG-IOT01A). I can't seem to find any example code or library for them or the Digital Filter for Sigma Delta modulators interface which it is connected to according to the schematics.

I did read that there might be some examples in the ST website but I couldn't find any code and I already have some code in mbed which I would like to use. I basically need to send the data from all the sensors over TCP. I have managed to for all except the microphone.

Any help is appreciated.

3 Answers

2 years, 1 month ago.

Hi, have you managed to solve the problem? I am facing the same issue.

1 year, 8 months ago.

Same issue.

Hi Ignacio, I hope it's not too late, but I got it working here: https://github.com/janjongboom/b-l475e-iot01a-audio-mbed

posted by Jan Jongboom 03 Dec 2019
1 year, 7 months ago.

I've pushed an example here: https://github.com/janjongboom/b-l475e-iot01a-audio-mbed - hope others find it useful too!

Hi Jan,

I downloaded, compiled and ran your program. I never see the hex dump step on the terminal.

With the serial monitor attached:

1. Hit the blue button to start recording.

1. After two seconds a binary file in HEX format will be displayed (in one line with no spaces).


Hello from the B-L475E-IOT01A microphone demo

OK Audio Init (Audio Freq=16000)

Press the BLUE button to record a message

OK Audio Record



posted by Kevin Braun 03 Dec 2019

Kevin, try compiling with --profile=debug flag... For some reason it indeed doesn't fire the interrupts in develop build, I expect some optimizing out of the interrupt handler. Will investigate.

posted by Jan Jongboom 04 Dec 2019


I saw no change in the behavior. I did notice this during the compile. Could this be an issue? Using GCC compiler

[Warning] @,: Compiler version mismatch: Have 6.3.1; expected version >= 9.0.0 and < 10.0.0


It is now working. Thanks

posted by Kevin Braun 04 Dec 2019

Not on my side... Compiling with the same compiler. If you drop me an email at jan at edgeimpulse dot com, I'll be happy to share investigate further.

posted by Jan Jongboom 05 Dec 2019