(08-27-2020, 06:57 PM)rdmarsh Wrote: * On boot using an external keyboard everything is fine
* As soon as any key is pressed on the internal keyboard, it goes to uppercase and gets stuck there. Numbers only type the shifted items (!@#$% etc)
* Running showkey (https://linux.die.net/man/1/showkey) and pressing left shift once keeps saying that 'keycode 42 press', which is left shift key. It's not physically stuck though and pressing it shows press and release for it as well.
Pressing any other key stops the constant stream of 'keycode 42 press', but still behaves as if it's stuck.
Only a reboot fixes it and lets me type normally on the external kb again.
Sounds like it's not getting a "key up" event. Some reasons for this can be:
* Kernel is busy, key presses get dropped in buffer - this can't be the case as the other keys work.
* USB bus is dropping packets - again this can't be the case as the other keys work.
* Bridge across switch - unlikely given these style of keyboards usually don't have traces exposed.
* Key switch is broken - most likely as just one key is affected.
Regarding the last two points, the way a keyboard will typically work is that it'll poll the traces and check the return. A key press is registered when the poll (a small electrical pulse) gets through the circuit and keyboard chip reads it.
To save on the number of pins required on the kayboard chip, typically these traces will be shared. If it's unlikely more than say 5 keys will be pressed at the same time, you can use diodes to share pins by pulsing in different directions. If this process was broken I would expect more than one key to be broken.
So my suggestion:
* Be sure that ONLY one key is exhibiting this behaviour. If you find it's more than one key, check any pins connections for a short (it could be some water damage, stray copper thread or something). Make sure any exposed metal is properly insulated from anything it could conduct on.
* If you are sure, follow a guide online to lift the key cap and clean it. Laptop keys can quite easily break when being lifted, so bare that in mind when starting.
* If you still have no success, you'll probably be better served by replacing the keyboard.
