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i.MXRT1064 EVK SD Card speed issue

Question asked by Jamie Robertson on Aug 16, 2019
Latest reply on Aug 23, 2019 by Hui_Ma

I'm using a GPIO pin and scope to time how long it takes to read a block of 4 sequential sectors from the microSD card on the MXRT1064 eval board. I'm used to seeing something on the order of 500 us or less on other processors, but am seeing more like 2 ms with this board. After stepping through the code, it's seems clear that a call to USDHC_SetAdmaTableConfig() is returning an error causing DMA to be disabled and the code to fall back to using polling mode.

 

The microSD card I'm using reports it's using timing mode SDR104, Freq : 198MHz

 

Any thoughts as to why the DMA is not being used? This happens with the unmodified "sdcard_interrupt" example project.

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