Keychron K2 keyboard

I have received a Keychron K2 keyboard for potential review in Archive – except I’m getting nowhere under RISC OS with the Raspberry Pi 4B. I have toggled the switch to “Cable” mode for wired connection but it seems to crash the Pi immediately, whether it’s plugged in from power on or after the Pi has finished booting up.

It feels like it’s sucking too much power for the Pi, except that: a) everyone reports that it works fine on Raspbi…Raspberry Pi OS and b) I’m using the official Raspberry Pi power supply which should supply plenty of power. So I’m at a loss. Any ideas where to start investigating?

I got a fancy keyboard (with LED lighting) and had to interpose a powered USB 3 hub between the KVM and the keyboard as it drew so much power the KVM could not handle it. Nothing in the documentation about the keyboard to warn about this. It’s power consumption is over 1.5A.

I’ve just finished to struggle with a mechanical keyboard (Durgod, all the details on the Bugs forum :) ).

The first suggestion I can give you is to power the Pi without the keyboard attached, then start the !HID application and try to connect the keyboard. This will load the USBHID module, that uses a different way to control the keyboard than the USBDriver one, more similar to the Windows / Linux / MacOS / every-OS-but-the-dishwasher-firmware one.
If it works, then there’s a bug on the keyboard firmware or in the USBDriver.
If it doesn’t and crashes the Pi, it could be a power issue (but you need a powered USB hub to exclude it), or a bug in the XHCI driver (hic sunt leones) that crashes the kernel at a lower level.
Do the keyboard lights (i.e. caps lock) turn on before the crash? This could indicate that the initial phase of the setup completed.

If nothing works you can play a little bit with the sysvars that configure the timings of the USB, but let’s go step by step.

It would be handy to have a extra Directory alongside the RO ROM for PI’s – that would act like Podule ROM dir’s in VRPC/RPCE.

Hi Salvatore, thanks for the suggestions. Yes, I tried !HID and I tried plugging the keyboard in before booting up and afterwards. No success. However, what I hadn’t realised yesterday was that the Pi isn’t completely frozen at all. The clock continues to stay accurate – it’s the USB ports that seem to fail until rebooting.

Do the keyboard lights (i.e. caps lock) turn on before the crash? This could indicate that the initial phase of the setup completed.

There is a quick flash of a handful of keys, but nothing like the keyboard’s usual startup sequence.

As Chris and you said, it points to power consumption. I checked the documentation and the only mention of requirements is a 5V 2A power adapter.
Next step: get a powered hub and try again.

The clock continues to stay accurate – it’s the USB ports that seem to fail until rebooting.

I have seen similar symptoms on a Pi 4 (keyboard & mouse froze; clock still running) when connecting a miniature SD card reader¹. The device started working when connected via an unpowered hub.

¹ This wasn’t a guaranteed failure; it seemed to work about 30% of the time. I did label it “Do not use on Pi 4”, though.

It would be handy to have a extra Directory alongside the RO ROM for PI’s – that would act like Podule ROM dir’s in VRPC/RPCE.

There’s an echo round here. That sounds much like my discussion with Gerph the other day.
I do agree the “Podule” directory would be handy.

Brief update: I charged the keyboard fully and, lo and behold, it worked beautifully for a couple of hours. Then I switched it to Bluetooth mode, so that it would work with my Mac, did a few things (thus draining the battery), and when I plugged it back in and switched to cable mode again, it immediately killed the Pi’s USB system. That all but confirms it’s sucking too much power.