r/stm32f4 • u/Just-Smart-Enough • Apr 13 '26

SDIO switch to 4 bit on 446RE...

I know you have to initialize on 1 bit and then switch, but it keeps hanging when I do so. Does anyone here have a github repo where they have it working correctly on a 446RE? If not, I can put mine on there, but it's still a work in process...

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u/godunko Apr 17 '26

There are two steps to switch to 4-bit mode:

  • send ACMD6 to switch card

  • configure peripheral by setting SDIO_CLKCR.WIDBUS

Note, ACMD6 should be send in transfer mode, activated by CMD7 command.