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SG.4
Visitor II
July 8, 2021
Solved

Hello ST Experts , I have a three VM3000 PDM mems interfaced to a STM32f745IETx controller , via I2S2, I2S1 lines and another in SAI2_SAIB block , how do I configure three such in programming while using PDM2PCM middleware , can anybody help me ?

  • July 8, 2021
  • 1 reply
  • 2634 views

The help will be greatly appreciated . I have to write this raw data extraction of PCM values in onto sdmmc sd card . And could anyone explain me how does the PDM2PCM functions for the mems than ST PDM microphones? I usually find examples of stm32 controllers with MP45DT02 ? and how do we conclude whether the conversion is accurate and PCM are correct values.

Thanks in advance.

    This topic has been closed for replies.
    Best answer by Eleon BORLINI

    Hi Shweta @Community member​ ,

    >> I have some basic doubts the middleware PDM2PCM outputting 16 bit PCM, does these sample obtains have any headers present or its just plain or do we need to add the headers?

    The .wav file has a proper header containing metadata about the raw PCM file, so I would say that the final .wav has of course ho contain header, but the PDM2PCM outputting has no header so you can process the signal starting from the first byte.

    >> I wanted some more help on ublox LARA-R211 4G LTE module testing with the stm32f745 [...]

    About this topic, I would suggest you a couple of actions:

    • First, since the 4G LTE module is from u.blox, you should try to ask for help in their community.
    • Second, you can try to post your question in a new Q&A, with the proper STM32H7 tag.

    If my reply helped you with your question, please click on Select as Best at the bottom of this post. This will help other users with the same issue to find the answer faster.

    -Eleon

    1 reply

    E
    Eleon BORLINI
    ST Employee
    July 12, 2021

    Hi @Community member​ ,

    did you already check the design tip that explains the use of the STM32Cube PDM2PCM software library?

    This explains how the PDM2PCM library converts a PDM bit stream from a MEMS microphone into a PCM audio stream: it provides details about the interface parameters and the configuration of the library. It also shows how to integrate this library into a main program, and applies to microcontrollers of STM32F4, STM32F7 and STM32H7 Series.

    -Eleon

    S
    SG.4Author
    Visitor II
    July 13, 2021

    Hi @Eleon BORLINI​ ,

    Hope you are doing good.

    Thanks for your help again in time ,I have gone through that document, yes

    Here in the work space have also used codec TLV320adc3140 with STM32f745 ,had just connected those mems microphones bypassing codec on I2S lines

    I could receive the WS,PDMCLK(approx 3.25MHz ) ,PDMData(768kHz o 1.025MHz )to on the scope.

    But when I debugged the PDMbuffer and PCMbuffer showed zero values ?

    ..

    But final one I have to get connected via the codec ..

    not much variations on the PDM mics so I had posted this query /

    I am not getting out ,could I be missing out on something.

    Thank you for the time and help.

    Kind regards

    --

    Shweta

    E
    Eleon BORLINI
    ST Employee
    July 14, 2021

    Hi Shweta @Community member​ ,

    the VM3000 microphone is from Vesper, so I suggest you to check also in their forum, whether they can help.

    However, I think that all PDM microphones works more or less in the same way, maybe varying the master clock (and sampling) frequency.

    You shouldn't need any external codec to connect a PDM microphone to an STM32F7, since the signal is acquired in blocks of 8 samples by using a synchronous serial port (SPI or I2S). Did you correctly configured these interfaces in the initialization part of the code? You might check example of the use of these interfaces in the X-CUBE-MEMSMIC1 function pack, in the \Projects\STM32F746ZG-Nucleo\Demonstration folder.

    Please let me know if this can be useful.

    -Eleon

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