我现在想用stm32F407系列的spi口来采集mp34dt05的PDM麦克风的数据，但是我发现我采集到的pdm数据流基本上不会因为我的环境变化而产生任何变化。你能详细告诉我spi是怎样的吗？要接收mp34dt05的数据，麦克风芯片mp34dt05有驱动文件吗？如果有的话可以发给我吗？感谢您的关注。
Translated from Chinese to English:
I am now trying to use the spi port of the stm32F407 series to capture data from the mp34dt05's PDM microphone, but I find that the stream of pdm data I capture basically doesn't change in any way due to changes in my environment. Can you tell me in detail how the spi works? To receive data from the mp34dt05, is there a driver file for the microphone chip mp34dt05? If so can you send it to me? Thank you for your attention.
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