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Joe Wright
Joe Wright
Associate
January 15, 2018
Question

Optimising for mono audio

  • January 15, 2018
  • 4 replies
  • 943 views
Posted on January 15, 2018 at 15:06

Hi, I'm prototyping something that processes digital mono audio from a mems mic, transferring the data over i2s into an stm32f373. The only issue I have is that the DMA transfer is designed for stereo so twice as much data is transferred than necessary, with the second channel being zeros.

I'm wondering if there is a more efficient design, perhaps with a different mcu, communication type, etc.., so that only the single audio channel is transferred.  As far as I can tell i2s will always give a stereo feed to the DMA.

Can anyone think of a mono optimised design?

Thanks, Joe

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    4 replies

    waclawek.jan
    waclawek.jan
    Super User
    January 15, 2018
    Posted on January 15, 2018 at 15:20

    What mic? Any codec?

    JW

    Joe Wright
    Joe WrightAuthor
    Associate
    January 16, 2018
    Posted on January 16, 2018 at 01:27

    So far I've used Invensense ICS-43432 or Knowles SPH0641LM4H-1 which work but as they use i2s the DMA controller on the STM32F373 includes the blank data for the non-existing channel.  I'm not using a codec.

    waclawek.jan
    waclawek.jan
    Super User
    January 16, 2018
    Posted on January 16, 2018 at 10:37

    SAI can selectively throw away portions of received data, or at least that follows from the RM, I haven't tried personally. I also believe the 24-bits could be handled better with SAI.

    SAI is to be found in some 'F4, 'F7 and 'L4; AFAIK no 'F3 has SAI.

    If you have intrinsic reasons for the 'F373, I could envisage some timer-based scheme to trigger DMA picking the data more 'selectively', instead of  'natively' triggered DMA; maybe some pins would need to be interconnected externally. This would need to be experimented.

    JW

    Joe Wright
    Joe WrightAuthor
    Associate
    January 16, 2018
    Posted on January 16, 2018 at 14:44

    Thanks, SAI looks good.  I'll have a play with one of the supporting F4's.

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