I saw the Arduino QT PY while ordering online and thought it would be perfect for a single key keyboard, being only slightly larger than a MX switch.
This is made with just a QT PY, two wires, a 1kohm resistor and a Cherry MX Blue switch. It has a really small amount of code to act just like a normal key. I could also make it a macro.
I have included the .ino to flash the arduino with. It is currently set to be the button f, easily changed by changing the ASCII number from " char button = 102;" to something else. It could also be easily changed to a macro.
Below is the basic wiring and there is also a photo of how the internals are wired above.
There is a pinhole on the front of the keyboard case so that the reset/bootloader button can be pressed with a pin.
EDIT: I have now included code that was found on the below post by user paa36308. for Morse code support !
https://forum.arduino.cc/index.php?topic=600356.msg4095406#msg4095406
Rafts:
No
Supports:
No
Resolution:
0.16 with adaptive layer at 0.7 at slanted top of main body
The author marked this model as their own original creation. Imported from Thingiverse.