Finally the keyboard PCBs have arrived from China.

For the keyboard, it is the final design. The size is 60x100 mm, and the intended position is to the right from the screen:

(The screen itself is still in the mock up stage). The keyboard has 4 LEDs and 60 switches - the one on the bottom left is a hardware power switch. All LEDs and keys can be accessed independently - in theory all 59 switches can be closed at the same time and will register.

The keyboard driver board sits below. A header for Arduino Micro Pro is provided, in case the keyboard is used as a standalone unit for PC.

Currently the driver board and the keyboard are connected by a header; the production version will be soldered.

The RPN calc can now impersonate a keyboard and a 3-button mouse, injecting keystrokes into a PC. Mouse pointer  movements and mouse wheel from  the calculator to the PC are also supported. With a dumb terminal, the RPN understands both the RPN and an Algebraic inputs:

The documentation is started at the project Wiki: https://github.com/ptravnik/Retro_CALC/wiki

Next: programming a File Manager!