Computing > Embedded Computing

32 bit CRC - is it standard?

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Siwastaja:
Best to use DMA to feed the peripheral.

If you end up just waiting for the DMA&peripheral in a busy loop, you could do part of the calculation in parallel with CPU, finding the optimal slice width, for example like processing 20% of the data in software while waiting for the DMA to do the trick for 80%, for most complexity for relatively little gain :).

I'm thinking, can you configure two DMA channels to trigger on the same DMA request signal, so that one of them moves the data to the CRC peripheral and another in memory? Probably not as reading out the SPI DR is the SPI FIFO pop operation.

peter-h:
ST offer a library (probably 1000 lines :) ) for using the 32F4 on-chip CRC generator but I decided to not pursue that because in my application I need to CRC check a data block produced externally, so needed a software version anyway.

In the context of what I am doing, running a CRC on even the entire CPU FLASH (1MB) in 400ms is good enough.

And in another part of the code I have to CRC up to 1MB coming off a 21mbps SPI FLASH chip, which is about 2MB/sec, so of the same order as doing it in software. One could fully hide the CRC calculation in the SPI transfer time in that case, if I wanted to unravel the SPI code which currently is a blocking function.

SiliconWizard:

--- Quote from: Siwastaja on July 30, 2021, 06:48:11 am ---Best to use DMA to feed the peripheral.

--- End quote ---

Yes. Obviously the most efficient way is to use the CRC peripheral along with DMA. Then, it'll be significantly faster, and most of all, you can do something else while it's computing the CRC on the whole block.

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