STM32H735G-DK - No data from on-board MEMS PDM microphone (SAI4_A in Master Receive mode)

[EllaGez]

Hello,

I'm working on a project using the STM32H735G-DK development board. I'm trying to receive audio data from the on-board digital MEMS PDM microphone (U33) using SAI4 Block A in Master Receive mode. I selected PDM mode in CubeMX and configured SAI4_A as Master Receive. SAI4_CK2 is set as the clock output pin, and SAI4_D1 as the data input. I’m using PLL3P as the clock source for SAI4A, set to 49,152. Middleware PDM2PCM is enabled. I’m currently using HAL_SAI_Receive() (not DMA yet), but BDMA is enabled.

When I run the program, the microphone always returns a constant value (like 0xFF), or no data at all.

Has anyone successfully used the on-board PDM microphone with SAI4 on this board? What is required to activate the SAI4_CK2 clock and receive valid data?

Thanks for the help.

[ahsrabrifat]

The onboard MP34DT05 is powered via VDD_MIC and enabled via MIC_CK, which is internally connected to SAI4_CK2.

If the clock is not toggling, the microphone stays inactive and outputs nothing or 0xFF.

[EllaGez]

In my code the clock is enabled, still wont work. The MIC gets 3.3V.