MSX – Using Sega Controllers

2Aug/170

MSX – Using Sega Controllers

The MSX uses the same port as many older consoles, so one might be mistaken for thinking that any controller will work. Unfortunately, regardless of the fact that they are all DB-9 ports, the wiring is often different. Below I'll show how to build an adapter to hook up both a Megadrive and Master System controller to your MSX.

Sega Megadrive Button mapping

Standard Megadrive controllers have 3 action buttons. MSX only needs two, so we'll use B and C for buttons 1 and 2 respectively; the reason for this is a little complex. The Megadrive controllers have 4 buttons but only 3 wires to read the state. This means that one wire acts as the switch to read either A/Start as a pair or B/C. As that we can't switch between these without more work, we'll just use the second state and read B and C independently. There's further reading here for anyone who wants to know more.

Megadrive Pin	Description	Mapped to MSX pin
1	Up	1
2	Down	2
3	Left	3
4	Right	4
5	+5 V	5
6	TL (A/B)	6
7	TH (Select)	5
8	Ground
9	TR (Start/C)	7

Wiring up a Megadrive adapter

A quick note: If you have no requirement to use the Megadrive controller in a real megadrive again, follow the instructions here instead. Otherwise you'll need a male DB-9 plug, female DB-9 socket and some wire. The shorter you make the wires, the better. Too much play, without securing everything with glue or in a case, will cause instability and/or break your solder connections.

For the most part, all wires are straight through. The only exception is to wire Pin 9 of the male plug to pin 7 of the female plug. This routes button B on the megadrive controller to button 2 on the MSX.

I cheated and hot-glue-gunned them for stability. A better method would be to buy DB-9 plugs and sockets with housings. Or find two long and thin bolts to create a frame between the two.

Sega Master System Controller

The pinout of these controllers is slightly different (see here for a diagram); the buttons are actually backwards compared to B and C on the megadrive. Therefore we're going to build the same adapter above but route (from male to female) 9 to 6 and 6 to 7.