I have a PDM-Mems Microphone which provides me with 101010 data, the Microphone has a Clock of 3Mhz. I read the manual about how PDM is generated, but I haven't worked with digital filters yet and in the manual only stands to use a Low-Pass. But I can't find a formula for a digital Low-Pass filter.

My question is how can I perform a digital Low-Pass with the PDM-Output data?

Microphone: https://learn.adafruit.com/adafruit-pdm-microphone-breakout?view=all

  • 1
    \$\begingroup\$ You don't need a digital low pass. You either need a counter (processing on the digital side) or you need an analog filter (to convert PDM to a voltage). \$\endgroup\$ Apr 29, 2019 at 8:28
  • \$\begingroup\$ The PDM-Signal is later used for a Speech-processing Neural Network, what do you mean with a Counter ? Like a sort of Counting algorithm and calculate the mean of the windows? \$\endgroup\$
    – FoldFence
    Apr 29, 2019 at 8:33
  • \$\begingroup\$ I'd just count the pulses within a given time. Many microcontroller have units that can do that for you, so that you just have to query a register every so and so many microseconds. \$\endgroup\$ Apr 29, 2019 at 8:48
  • \$\begingroup\$ Ah ok, so I first must have a look on the windowing and later then average each window and look at the differences to the first window if I understand it correctly. Thanks for your help =) \$\endgroup\$
    – FoldFence
    Apr 29, 2019 at 9:14


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