Another milestone reached

Good news, SDIO is working, including an upgrade from Petit FatFs to FatFs.

Basically there were 2 problems. Some time ago I ripped some stuff from the breadboard to tidy things up a bit. Unfortunately this included a wire connecting the PSU to the right most power rail. As fate would have it this is where I attached the 3,3V of the SD card socket to a few days later. As long as the missing connection was well.. missing, the SD card was powered by the SDIO signal lines through the pull-up resistors. This resulted in unexplainable behaviour such a Kinston card to timeout at CMD8 and a Sandisk card never completing the voltage validation cycle.

The other thing were CRC errors during transfers. 25 MHz is simply too much for the current setup, which in all honesty isn’t really surprising given the long and poor connections. A real PCB and some pull-up resistor tweaking should make a speed increase possible. Currently it’s running at 4,2 MHz (simply because 0x0F is an easy to remember CLKDIV value ;)), but what this means in data throughput numbers… no idea yet.

Oh and it uses DMA, which also is a nice addition!

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