Connect MSX Joysticks to the Gigatron TTL microcomputer.
Note
No build instructions are yet provided, but if you are brave enough go for the recommended build.
The gt-joymsx v1 is an adapter that allows connecting MSX joysticks to the Gigatron TTL microcomputer.
The main features of the gt-joymsx v1 adapter are:
- small footprint
- made of widely available electronic components
- behaves as a cord extension between the Gigatron TTL microcomputer and the MSX joystick
- uses an extension cable with a female DE9 connector on the adapter's Gigatron TTL microcomputer joystick side
- uses a male DE9 PCB connector on the adapter's MSX joystick side
- no need for external power supply, the adapter draws current from the Gigatron TTL microcomputer joystick port
- super low power consumption
The Gigatron TTL microcomputer uses 9-pin Famiclone compatible joysticks. Those joysticks use a Texas Instruments 4021 or compatible to latch and serialize the information about the pressed joystick buttons and arrows.
The standard MSX joysticks are completely passive and have parallel signals for each of the buttons and arrows. The MSX computers pull up by default the signals when a MSX joystick is connected, and the MSX joysticks pull the signals to the OUT signal (pin8) when buttons or arrows are pressed (see page 27 of MSX Technical Data Book for a schematic).
The gt-joymsx v1 adapter uses a CD4021BM integrated circuit to convert the signals from the MSX joystick buttons and arrows to the 9-pin Famiclone expected signalling.
As the MSX joysticks lack the SELECT and STARTbuttons of the Famiclone joysticks, the gt-joymsx v1 adapter itself also provides two Cherry-compatible key switches to add those two buttons.
A two-sided printed circuit board (PCB) is used to put together all components:
- An angled Sega DE9 PCB male connector is used to directly connect the MSX joystick
- A PH2.0 connector is used to connect the Gigatron TTL microcomputer joystick cable extension
- Two Cherry-compatible key switches to implement the
SELECTandSTARTbuttons - the CD4021BM CMOS 8-Stage Static Shift Register
- A pair of pull-up resistor networks to provide default signals for buttons and arrows
Connection to the Gigatron TTL microcomputer joystick port is implemented using a DE9 joystick extension cable with a female DE9 connector on one side and a loose end on the other side. The joystick extension cable loose end is wired according to the following pinout mapping.
 |
|---|
| Gigatron TTL microcomputer joystick connector pinout, from adapter extension cable plug side |
| Gigatron side pin | Cable color (may vary) | Signal |
|---|---|---|
| 1 | Red | unconnected |
| 2 | Black | SER_DATA/D0 |
| 3 | Grey | SER_LATCH/OUT0 |
| 4 | Orange | SER_PULSE/CLK |
| 5 | Brown | unconnected |
| 6 | Green | +5V |
| 7 | White | unconnected |
| 8 | Blue | GND |
| 9 | Yellow | unconnected |
| MSX side pin | Signal |
|---|---|
| 1 | UP |
| 2 | DOWN |
| 3 | LEFT |
| 4 | RIGHT |
| 5 | +5v |
| 6 | TRIGA |
| 7 | TRIGB |
| 8 | GND |
| 9 | GND |
Please, use gt-joymsx-v1 Build1 for making boards.
This board has been successfully built and works fine.
A simple acrylic enclosure design for the project is provided to protect the electronic components and provide strain relief for the extension cord.
The enclosure uses a 5mm acrylic sheet.
- By using this adapter in combination with a msx-joyblue adapter you can play games on the Gigatron TTL microcomputer using bluetooth adapters (for example, you can play Racer using a Nintendo Wii Remote with a Wheel)
Gigatron TTL microcomputer
MSX general purpose I/O port
Famiclone pinout
4021 pinout
