So,

Now that qwerty PCB is ready, looks like I have to adjust it ;)

I need to try something with real raspberry, it's not currently clear if direct serial communication between raspberry and arduino is OK for programming or I need some logic level adjustment circuit.

Also since it's arduino targeted programming Pi Zero hat, it would be nice to add ISP header, looks lik there are some tutorials and this should be possible with raspberry, although again the question is about signal levels. AND about pcb space - I almost don't have it at all.

ToDo - Test real arduino with real raspberry. It would be awesome to win one, in the meantime I have to use someone else's device.

ToDo - With respect to using the keyboard - here is what I'll need to do on boot:

1. autostart Xserver with x11vnc enabled and with low resolution (suited for smartphone display)
2. auto-launch xterminal in the GUI session with screen command

This way it doesn't matter how you are connecting:

- Via VNC client - you'll see the console X session and will be able to use qwerty directly

- Via SSH client - you'll need to login into the multiuser screen session, again you'll be able to use qwerty in this case (already tested)

Smartphone connection for now is going to be USB, Bluetooth for the future

Big question is power, as usual. I decided not to spend time right now reserching harvesting it from mobile phone, instead let's add battery and charging circuit in between Pi Zero and Qwerty hat

ToDo - Desing battery and charging PiZero hat, there should be a way to remove it completely, because if you have apower source it's necessary for the device itself.