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problem with PDM_TO_PCM converting on STM324xG_EVAL board

Question asked by rizzo.adriana on Jul 5, 2015
Latest reply on Jul 6, 2015 by chahrayar.chahrazed

I want to use  ST MEMS microphone (MP45DT02) on STM324xG_EVAL board, I used an extension board and attached the digital microphone to the board. It works very well with Audio_playback_and_record code, but I have to increase size of InternalBuffer (INTERNAL_BUFF_SIZE) because I have some problems whit fast calling the BSP_AUDIO_IN_HalfTransfer_CallBack andBSP_AUDIO_IN_TransferComplete_CallBack.

The value of INTERNAL_BUFF_SIZE in code has been defined as:                  


When I try to increase this value, I encounter serious problems in PDM_FilterXX_XX (inBSP_AUDIO_IN_PDMToPCM function).

My questions:

1-      1-Can I increase the value of INTERNAL_BUFF_SIZE? Which value should I use?

2-      2-Dose PDM_FilterXX_XX ‘s input and output (uint8_t* data, uint16_t* dataOut) have predefined and constant size or I can increase them?

  • When I increase it, the quality of voice drop and it becom really unclear.