I've just purchased a couple of external numeric keypads for my kids' laptops. One is running Lubuntu 20.10, the other is running Ubuntu 20.04, but both are experiencing the exact same behaviour.
On plugging in to the USB port, the num-lock light illuminates and the keyboard works for approximately 1-2 seconds. After that, the light remains on (and num-lock is now enabled on the built-in keyboard), but the external keyboard is non-responsive. Disconnecting and re-connecting makes it work again for the same time period as before.
I've seen various similar posts (especially Keyboard stops working on Ubuntu 16.04 (Xenial Xerus)), as it seemed very similar, but none of the solutions seem to help. Things I've checked (mostly on the Lubuntu system, but I think the Ubuntu one's the same):
- I'm not running laptop-mode-tools or PowerTop
- I've located the device in /sys/bus and power/control is set to "on"
- /power/autosuspend_delay_ms is set to -1000, but setting it to -1 (as suggested by various guides) has no effect.
- If I toggle num-lock on the laptop keyboard, the light on the external one doesn't change, so it clearly doesn't get updates once it's in its frozen state.
- Num-lock is only activated on the laptop keyboard after I've pressed something on the numeric pad.
- Behaviour is exactly the same if the device is plugged in before I power up. The machine works fine. I type a character or two and then the external keypad is dead.
After some experimentation, I think the issue happens a couple of seconds after the first key is pressed and not from plugging it in.
The keyboards both work flawlessly on my desktop Windows machine, so I'm fairly certain this is a software issue. Are there other configuration changes I can try?
Update: Following suggestions in the comments, I've tried running a different O/S from a USB stick. The first that came to hand was PIXEL. The keypads both work fine with a Raspberry Pi Model 3, so it seemed like a good one to try. Interestingly, the behaviour is the same. The keyboards work for a few seconds then stop dead. This suggests to me that it's potentially something in the hardware / firmware and maybe not strictly Ubuntu.