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andysworkshop / usb-microphone

A USB Microphone built with an INMP441 and an STM32
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How to realize "Take the most significant 16 bits" #5

Closed Mountain03 closed 2 years ago

Mountain03 commented 2 years ago

Thanks for your project which gave me a lot of help,but there is one point I dont understand;

int16_t sample = (data_in[0] & 0xfffffffe) | (rand() & 1);

How can this" take the most significant 16 bits and respect the sign bit" ? I think this can only take the lower 16 bits without sign bit. thanks

andysworkshop commented 2 years ago

Hi, the short answer is that it's because the DMA peripheral reverses the word order in memory. The long answer is given in one of the comments on the article in my website.