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Use MEMS microphone to record audio with STM32F1 MCU

MAndr.233
Associate III

‎2019-10-19 03:32 PM

Hi,

I'm sorry if i'm asking anyhting newbie.

I want to use an STM32 MCU to build a voice recorde application. The data is acquired by a mic and stored in SD Car which connects via SPI with MCU. However, I've some doubts about my application.

  1. Since I need a sample rate like 40khz, due to the human voice spectra, are a MEM mic enough?
  2. Due to the high sample rate, I can transfer the raw data to SD without fullfill the MCU internal memory?
  3. Mems microphone will give me a great sound quality?
  4. Do you sugest me any references to read, since I'm very new with this topic?

Any help would be apreciated,

Best regards

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Eleon BORLINI
ST Employee

‎2019-10-21 04:06 AM

Hi @Community member​ , we have unfortunately no reference design publicly available that already puts together a STM32F1 + MEMS mic to give you an example project to start your application, but the answer to your question is positive in almost all the cases. Here below the details:

  1. MEMS mics are enough also for high-band application, so the answer to your question is "yes". ST portfolio includes two families of MEMS microphone: analog microphone (such as MP23ABS1) and digital microphone (MP34DT06J and MP23DB01HP). Analog mic is low power consuming but the acquisition with a MCU requires an ADC and it is not so simple to be managed. For this reason I suggest you to consider a digital microphone: the maximum detectable frequency depends in this case from the mic clock frequency. For example, if the clock is 2.4MHz and the decimation x32, you will get 75k samples per second, meaning 37.5kHz maximum frequency, well enough for your purposes.
  2. yes you can, but to avoid latency you could for example fill a buffer of e.g. maximum 1 second saving it temporarily in the internal MCU memory and then move it in the SD card
  3. If properly powered (e.g. clk 2.4MHz and Vdd 1.8V or 3.3V), digital MEMS microphone can reach >64dB(A) and AOP >120dBSPL along the audio BW. So for most of the application this is a great sound quality. Which specs do you have?
  4. I suggest you the existing reference designs the Bluecoin reference kit or the NUCLEO kit X-NUCLEO-CCA02M1, which is however quite old

Regards

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