Component for MEMS PDM Digital Microphone

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stefan.erni
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Component for MEMS PDM Digital Microphone

Post by stefan.erni »

Hi Ben

What about a component for a PDM microphone?
There are many small, inexpensive PDM microphones . These are available for smd soldering, as a small board or built into a housing with a groove connector. Sometimes you can find these PDM microphones on many ESP32 demo boards.

regards

Stefan

Here from Adafruit with groove connector
PDM_Mic_2021-01-15_18-35-38.png
PDM_Mic_2021-01-15_18-35-38.png (268.55 KiB) Viewed 2925 times
adafruit-pdm-microphone-breakout.pdf
(3.36 MiB) Downloaded 157 times
Or the Mic in a Case with groove connector ( U089 with SPM1423HM4H-B)
Mic_2_2021-01-15_18-38-02.png
Mic_2_2021-01-15_18-38-02.png (60.76 KiB) Viewed 2925 times

BenR
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Re: Component for MEMS PDM Digital Microphone

Post by BenR »

Hi Stefan,

Looks interesting, though reading up on it it looks like you need a peripheral on the MCU to drive it. Looks like some I2S peripherals might e able to drive it so I'll keep it in mind while I'm looking at the I2S stuff.

stefan.erni
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Re: Component for MEMS PDM Digital Microphone

Post by stefan.erni »

Hi Ben

I found some more info (Parts Pdf and Youtube Video) about MEMS Micros

I still have no idea how to use in FC

regards

Stefan

AN5027ApplicationNote-3.pdf
(1.83 MiB) Downloaded 243 times
Infos and Videos and Demoboards
https://eu.mouser.com/new/stmicroelectr ... nt=5918265

All about MEMS Micro

stefan.erni
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Re: Component for MEMS PDM Digital Microphone

Post by stefan.erni »

Hi Ben
Looks interesting, though reading up on it it looks like you need a peripheral on the MCU to drive it. Looks like some I2S peripherals might e able to drive it so I'll keep it in mind while I'm looking at the I2S stuff
I have read more about the MEMS Microphone. There are two type of MIC, PDM and I2S. So I'm more interested in the I2S MIC.
This MIC looks easier and more practical than the PDM and the I2S Bus can be use for much more than a just MIC.

So my wish changed to a component for the I2S bus and not special for the PDM MIC.

What I know that some PIC32, STM32, ESP32, raspberry pie have few I2S ports already

I'll take a look at my PIC32MZ2048EFG100.It should have 6 of theme.

regards

Stefan


some info about the two MIC: PDM vs I2S
digital microphones are available with two different output formats: PDM and I2S. The output of a PDM (pulse density modulation) microphone is a 1-bit high sample rate data stream that is the direct output of the Sigma-Delta modulator that's in the mic. The sample rate of this PDM stream is typically between 1 and 3.25 MHz. Before this PDM data can be further processed, it needs to be decimated to a lower sample rate that other devices, such as codecs and DSPs, can handle.
This decimation filter is implemented in the codec or DSP to which the PDM microphone is connected. The output of this filter gives data at a lower sample rate, typically between 16 and 48 kHz.
A microphone with an I2S output, has all of the same pieces of the signal chain as the PDM chain, but the places where each piece is implemented is slightly different. An I2S output digital microphone includes the decimation filter, so its output is already at a standard audio sample rate that's easy to interface to and process. Since this filter is implemented in the microphone, the Mic can connect directly to a DSP or microcontroller with an I2S input. This saves components in systems that don't otherwise need an ADC or codec, and saves the processor from the burden of implementing the decimation filter, either in hardware or in software.
A PDM microphone does have other advantages over an I2S mic. The PDM microphone typically has a smaller footprint, and only requires two signals (clock and data) for operation, while I2S requires three (data, frame clock, bit clock).

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