I think it’s worth pointing out that the process is not strictly reversible – there’s no known way to back up the existing firmware. It’s also not clear what the official status of the “original” firmware images linked from the OpenInkpot wiki is. They’re certainly not an exact match for the firmware which was pre-installed on my device (going by the version number).

In my particular case the procedure for installing the “original” firmware images didn’t work – I’m “stuck” with OpenInkpot for some reason. I reported this but no-one has any suggestions. I’m very happy with OpenInkpot, but I wouldn’t recommend installing it unless you know it’s what you want, and you’re prepared to accept the risk that the process might not be reversible.

Holding down the OK button doesn’t go into sleep mode; it does “lock screen”. Just like a mobile phone – it stops it from responding to (short) button presses while in your pocket or whatever. I’m surprised if the original firmware lacks this feature.

The hardware *does* have a sleep mode. I have no idea what the original firmware does (although I do know it shut down automatically after an hour or so of inactivity, which was rather annoying). But I do know that OpenInkpot automatically enters a (supposedly) low power consumption “sleep mode” automatically, after some period of inactivity.

I have a linux box, and I followed the instructions to SSH into OpenInkpot. If you’ve left the device powered on and inactive for some time beforehand, and then run “dmesg”, you will see the evidence in the kernel log. It shows the same lines as when you suspend a standard linux system. I haven’t bothered to find out what the timeout is though.