I located some old strip board on which to terminate the USB keyboard encoder taken from an spare keyboard. The strip board had previously been used in unfinished project as a cartridge port for one of my Synthesizers, so it had a 30 pin female header attached. I could have used this to plug in the USB encoder PCB, but elected instead to fit a male 30 pin header to the PCB and then terminate the 27 control wires from the USB Encoder PCB to female header sockets. This way it can be unplugged to allow additional PCB connections to be made or swapping out of encoders if the need arises.
The sockets are arranged form 3 time 9 pin sockets and a 3 pin socket. The 3 pin socket is purely there as a spacer and is intentionally left devoid of wires. One of the 9 pin sockets contains a ground connection and 8 wires that attached to one side of the original keyboard membrane. I have called these A1 to A9 in my matrix.
The other side of the keyboard membrane consist of 18 contacts B1 to B18 in my matrix. This is formed of 2 more 9 pin sockets.
Obliviously this could have all been made much smaller but as it is all going in a full size arcade style cabinets eventually, so I left it all as is.
I have mounted the USB keyboard encoder onto the interface PCB using a couple of standoffs. Rather then disturb the straight though strip board connections drilling mounting holes, I simply used a glue gun to mount the standoffs to the strip board. I also used the glue gun to dress the USB cable.
While I could use the remaining header socket to my joystick and control buttons. I figure that it might be desirable to be able to easily terminate one or more wires bu screw terminals. Particularly while testing. So at the opposite end of the PCB I have added PCB terminal blocks. I have organised these to cover just the 27 wires used in the Encoder. As the pitch of these is terminating a every other strip board track, I have staggered two sets back to back. These Organised as odd numbers and even numbers, 2 time 9 terminals for the “B” matrix connector. Then a 5 odd numbers terminal and 4 even numbers terminal for the 9 way “A” matrix connections.