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i.MX8M Mini PDM SNR issue

Question asked by m.c on Jul 9, 2019
Latest reply on Jul 18, 2019 by igorpadykov

Customer modified the definition of OSR in fsl_micfil.h from 0 to 8 as below to let PDM clock worked at 3.072MHz when recording by 48KHz sampling rate.

#define MICFIL_CTRL2_OSR_DEFAULT  (8 << MICFIL_CTRL2_CICOSR_SHIFT)

 

Customer also set “MICFIL Quality Select” to 1 and all “CH? Gain” to 15 , but recording SNR becomes to very low.

 

Read back MICFIL Control register 2:

root@imx8mmevk:/usr# /unit_tests/memtool -32 0x30080004 1

E

Reading 0x1 count starting at address 0x30080004

 

0x30080004:  02080010

 

How to improve recording quality?

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