Dual PDM Mic input on H7 with 16 Khz. Cube MX produces completely wrong clocks?

[AnkhInnovationsLLC]

Hello,

We're trying to configure the H7 for use with 2x PDM mics, with an effective sample rate of 16 kHz. I believe the input clock to the microphones them selves should be 2.048 Mhz, yet CUBE MX produces an AudioFrequency field value of 16 kHz?

Strange, the examples for the F7 boards use the proper frequency when interfacing with PDM mics.

Is it a bug or am I understanding the values incorrectly...

 

[Ghofrane GSOURI]

Hello @AnkhInnovationsLLC 

First let me thank you for posting.

I recommend you to  check   AN5027 Application note :  Interfacing PDM digital microphones using
STM32 MCUs 

Thx

Ghofrane

[AnkhInnovationsLLC]

Yes, I've seen this... Yet that only provides information on configuring the .ioc, nothing really else. The documentation is terrible. Why are the old PDFs again and not online somehow?

The clocks seem completely wrong. Even if you put the SAI into Master or Master with clock, it only cares about the "Audio Frequency", which is completely wrong. Also, although not for PDM mics, in this mode there is no way to set the MCLK anymore in the SAI parameters.

When did this change occur? The old versions had proper clocks in Mhz... 

[Piranha]

Why are the old PDFs again and not online somehow?

Searching a 2000 page PDF reference manual or even several PDF files at once and returning a result list takes just a few seconds. A web page... just cannot do it at all. So it doesn't add anything useful, but brings along a bunch of limitations.

https://superuser.com/questions/1630968/pdf-equivalent-of-notepads-find-all-in-current-document

https://superuser.com/questions/536153/is-there-any-way-to-search-for-phrase-in-multiple-pdfs-simultaneously