required I2S clock frequency

[KK Y.1]

Hi, I am using MP34DT05TR-A microphone with stm32f401re mcu. What is the I2s clock frequency required to get 24bit data at 48Khz sampling frequency. I also need to know the rate at which the data will be received from I2S?. Is it same as the sampling frequency?. Please provide your fedback.

[waclawek.jan]

MP34DT05TR is not I2S but PDM output, so you'll need to perform filtering and deicimation (a.k.a. PDM-to-PCM conversion). PDM is 1-bit, so in ideal world 24 bit * 48kHz = 1.152MHz. The PDM-to-PCM conversion is not that straighforward, but then also microphone's dynamic range is far from granting 24-bit "resolution".

According to MP34DT05TR datasheet, fCLK - Clock frequency for normal mode - min.1.2 MHz, max. 3.25 MHz - so that gives you the usable range anyway.

JW

[KK Y.1]

Hi,

Thanks for your reply . Based on dm00380469-interfacing-pdm-digital-microphones-using-stm32-mcus-and-mpus-stmicroelectronics.pdf we have understanding of getting PDM samples in stm32f40re through I2S. So can we obtain the 24 bit 48khz PCM data by using PDM2PCM library available for stm32 after receiving 16bit 48khz data from MP34DT05TR. As we are in intial software design stage we need this information.

[waclawek.jan]

I don't use the PDM2PCM library, so I don't know.

Presumably you are talking about 16 bit 48kHz stereo, which would correspond to cca 1.5MHz, that sounds OK.

JW

[KK Y.1]

Hi,

Thanks for your reply.