As I have a fix for the missed reverse problem that Defender players sometimes suffer from I want to make the solution available to anyone building a Defender game based on a MAME system.
So here I offer the USB encoder that I now use on my panels. It has up to 24 digital inputs, and a corresponding number of earths (and +5V pins, handy for optical devices). I offer it with MAME standard keys, or my modified keys (ALT,CTRL not used), or custom keys. The encoder has a micro-usb socket (which is thru board soldered at 4 points, so is not delicate like some arduino clones).
I haven't set these up as a shop, so email me if you are interested and let me know what inputs you need. If you are doing something interesting like Defender+Tempest or Defender+Missile Command I can add optical spinner functionality too.
I wire my panels using dupont connectors at the encoder, and dupont at the joystick (if possible eg JLF-01 or LS55-01) otherwise solder at the controls. Thus I'm normallycutting and stripping one end of the pre-made dupont wires.
£20 24input encoder with dupont headers unsoldered.
+£3 soldered headers for 14inputs, 14earths, 4x5V
+£4 soldered headers for 21inputs, 21earths, 4x5V
+£5 soldered headers for 24inputs, 23earths, 4x5V
+£2 custom mapping 14inputs
+£3 custom mapping 24inputs
15p 40cm Dupont female to female. Use as is, or cut and strip ends to make 1 or 2 connection wires.
10p 30cm Dupont female to female. Use as is, or cut and strip ends to make 1 or 2 connection wires.
10p 20cm Dupont female to female. Use as is.