SDHC with DMA in START-Project SAMD51

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Hi all!

I am trying to setup a Project for a datalogger which uses the SDMMC-Interface of the SAMD51, 48MHz DFLL.

The mcu reads per SPI from the AFE, formats and writes to the SD-Card. The data-rate is about 25 kB/s.

With FatFS there are a lot of dropouts. So I decided to write blockwise directly to the SD. This is working so far. Anyway, I get every 2,5s 60 or 100 ms gaps in the data writen. Beside one pinchange-controlled interrupt all other activities seeme to be blocked during the writing activity. I tryied to optimize it with using 2 buffers 128 blocks each alternating.

Now I saw, that the START-derived code works with a by word writing and I assume, that everything is diabled duringthe writing.

My question is, how it is possible to use a DMA-mode of the SDMMC-Interface to make other activities possible again during the writing.

Does anyone have experience how to modify this?

Thanks !!!!

Jun

Regards Wei Jun

Last Edited: Wed. Jul 29, 2020 - 03:25 PM