What is it?

Used to hook up a PS/2 keyboard and/or PS/2 mouse to a custom CPU or FPGA card.

• Two PS/2 connectors
• Power options for 3.3V or 5V
• 3.3V/5V Host and 3.3V/5V Keyboard/Mouse
• Option for bi-directional level translator (TXS0104 - U1)
• Bypass resistors

Why did you make it?

I like retro-computers. Most of the retro-computer projects use PS/2 keyboards due to the ease of interfacing. I found panel mount connectors nice but hard to find and somewhat expensive.

Also, I really do not like the way that many design put 5V to the keyboard and rely on series resistors alone to drop the voltage into 3.3V parts. The bi-directional level shifter on this card cleans this up so that the 3.3V side is supplied by the host.

Finally, some keyboards work just fine with 3.3V power but not all work. I've seen keyboards which look identical but one would work and the other did not work. That's why I wanted a clean level shifter.

Why do you sell it as a PCB not assembled

There's a couple of reasons for this. One is it's less expensive to ship a PCB. Another reason is that there are a few build options. The third is the cost of the PS/2 connectors. These are very cheap from China but relatively expensive from US distributors. You can choose which part source you want to use.

What makes it special?

There's some cool options. Like just using resistors to connect the CPU and keyboard/mouse. Or having a level translator to convert between 5V and 3.3V. That way you can run the keyboard at 5V and your host at 3.3V.