FatFs/SDMMC with 4 wires times out, 1 wire works

[Lars Beiderbecke]

I'm still trying to get FatFs to work with 4 wires. My PCB has been properly traced, each line is within a few mm of all others, and has a 33K pull-up. Internal pull-ups are off.

This setup works fine at full-speed (45 MHz) when using only 1 wire, but when I select all 4 wires in CubeMX, the code hangs in stm32f7xx_hal_sd.c, in the /* Poll on SDMMC flags */ loop. It probably should time out, but doesn't. This doesn't change if I lower the speed to 3 MHz.

My concern is not the timeout, though, but why 4 wires are still not working. Could someone advise on my PCB if everything is alright there? Are the pull-ups placed OK? The SD1 trace accidentally hit the resistor pad, but is this already enough to mess everything up?

(Note that seemingly unconnected resistors are connected by copper pours.)

[Tesla DeLorean]

Thank you, got the mail.

I was leaning toward double checking the pin ordering on the socket.

Just glad it wasn't something like cross-talk.

Having something independent covers potential issues with clocks or pin configurations.

[Steve Melnikoff]

Possibly related question.