I'm using the Raspberry Pi OS 64-bit version, updated to current, on a 4B with 8 GB RAM and a 512 GB SSD via USB3. I'm trying to use it with an IBM 122-key Model M keyboard with a custom STM32F411 BlackPill controller in it that talks USB-C. The controller is running QMK. When I plug the keyboard into any of my Pi's USB ports, I get no response out of it, and dmesg just shows usb: connect-debounce failed. I can plug the same keyboard and cable into a couple of different PCs and it works fine. Other keyboards plugged into the Pi in the same USB port work fine.

Update: It's specifically the BlackPill controller version. Ihave another identical keyboard, running identical firmware, but on a Teensy++ 2.0, and that one works fine.

There's some sort of compatibility issue here, but what?

1 Answer 1


It started working after I set the QMK firmware's USB_MAX_POWER_CONSUMPTION to 50 from 500 and then power-cycled everything. I'm not entirely sure this fixed it, but I can't get it to break, so I'm calling it fixed.

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