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# PDM microphones

`lib_xua` supports input from up to 8 PDM microphones although this is extensible.

PDM microphone support is provided via lib_mic_array. Settings for PDM microphones are controlled with the defines in Table 24.

Table 24 PDM defines
Define | Description | Default
--- | --- | ---
`XUA_NUM_PDM_MICS` | The number of mics to enable (0 for disabled). This enables compilation of the PDM to PCM code also. | `0` (disabled)
`PDM_MIC_INDEX` | Defines which starting input channel the mics map to | `0`
`XUA_PDM_MIC_FREQ` | Defines the PCM output sample rate of `lib_mic_array` | None (must be defined)
`XUA_PDM_MIC_USE_PDM_ISR` | Define as 1 to enable merging of the PDM receive task and decimation task into a single thread using an ISR | `0` (use separate threads for PDM and decimation)

Note

Currently only a single, fixed sample rate is supported for the PDM microphones

Note

Setting `XUA_PDM_MIC_USE_PDM_ISR` is only recommended for PDM mic counts below 8.

Please see the PDM Microphones section for further details.