The uPF--2.

The Wichit Sirichote Z80 MICROPROCESSOR KIT clone : The uPF--2.

I worked on replacing the Wichit kit with an FPGA version. During this work, I said to myself that the keyboard had to be replaced. On one hand because I think that it is impossible to work under good conditions with the original micro-switches, and on the other hand, the multiplexing has not been correctly implemented and can present big problems in the event of simultaneous pressing of several keys. No protection diode and no phantom key suppression as been placed : 

The Wichit Sirichote original design.

Furthermore, I decided to recreate the keyboard as a separate part. This will allow me to develop the processor board independently. However, I also decided not to use a parallel link because it is not practical at all. I preferred to connect the keyboard with a simple serial cable to the processor board.

There are not many solutions for the choice of keys if you want something 'pro'. So I chose the Cherry type keys. For now, I have only studied the keyboard circuit. Here's what it should look like :

To be continued...