PDM sample resolution

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fly135
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Location: Orlando, FL

PDM sample resolution

Postby fly135 » Tue May 14, 2019 6:17 pm

I could write a test app, but I thought maybe asking the question would be quicker, and maybe reveal something I would overlook in a test. I'm currently sampling PDM audio at 16 bit, but find the audio at normal levels is pretty poor, especially on mics with low sensitivity (-46dB). The mic INMP621 docs don't specifically talk about data resolution, which leads me to believe that's part of the codec in the ESP32 driver. So I'm wondering if I up the sample resolution to 32bit, what should I expect to get? I've searched for other ESP32 PDM mic projects and it seems like everyone is using 16bit.

John A

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fly135
Posts: 606
Joined: Wed Jan 03, 2018 8:33 pm
Location: Orlando, FL

Re: PDM sample resolution

Postby fly135 » Tue May 14, 2019 10:32 pm

I had written a simple app in Arduino that tests the board to see if I get reasonable values out of the various components for a manufacturing test. In that app I read the mics and calculate the RMS of each block of audio. When I switched the PDM mic from 16 (works) to 32 bit I got nothing out. The non-PDM mics are 32 bit and function fine.

Quite frankly I don't find Arduino to be reliable. Sometimes I have to reset several times before it will recognize all of the I2C based components. But it never had a problem with I2S.

John A

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fly135
Posts: 606
Joined: Wed Jan 03, 2018 8:33 pm
Location: Orlando, FL

Re: PDM sample resolution

Postby fly135 » Thu May 16, 2019 4:06 pm

Bumping this because I think there is an answer out there and it got pushed off the front page too quickly and was missed.

John A

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