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
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Hi,

Did you ever solve this issue? We recently run into this exact same thing and are hoping others have made progress on this front before we start working on it. Atmel START only provides a synchronous driver for SD communication which doesn't make use of the SAMD51's SDMA and ADMA within its SD/MMC Host Controller. Do anyone know if the older ASF supported this?

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Hi,

I just read your question.

No, I didn't solve it, sorry. But I am interested in a solution. Maybe in the future i will try again.

 

Regards Wei Jun