GameTrak is a controller that was used by a few games on Playstation 2, and later also PC, and Xbox.
See images, but more interestingly, look at videos like Game Trak Theory Ge Wang: The DIY orchestra of the future, Line of voice and string －for Game-trak controller, Kyma system.
Device internals are fairly simple, two copies of:
- a wire spool (middle area) that rotates a potentiometer as it is pulled out
- ...physically threaded through the middle of an analog joystick (on the sides) much like those in gamepads.
- Which is one pot per axis
All pots are 5kOhm.
The IC on the board is epoxy-blob'd, so presumably custom.
While PS2, PC, and XBox variants all look the same and are all connected through USB, they are not quite interchangeable out of the box.
Some revisions can be easily tweaked, others not.
All boards are USB, so all are detected fine on a PC (name, HID, layout).
...but Rev1 is PS2-only will in that it will not seem to output any values on PC. (I've always assumed such incompatibility between consoles was intentional, and at data level rather than USB level).
....while rev2 can be bridged for PS2, Xbox, and PC - it's even silkscreened as such.
They probably developed it for PS2 initially, then decided they wanted to release it for other platforms.
Interfacing one with software
If you have a rev2, then you take a few minutes to solder-bridge it for PC and you're ready.
...ready for for anything that takes joystick style input, that is, which e.g. most music production software allows in some way or other, be software like ChucK or Kyma or Max behind it, or DAWs that can take joystick-like input.
I also have a rev1.
It's presumably possible to create a PS2-gametrak-specific driver to deal with the different format, but not really a convenient solution in that most platforms do not make custom drivers very easy to use (and it being HID doesn't make that easier).
So this became a DIY project instead:
Your own hardware
The potmeters are all 5kOhm, so putting them across Vcc and Gnd is fine (takes a few mA in total at 5V), and the middle to an ADC doesn't even need any extra components.
All you need is a board with an ADC that muxes to at least 6 pins (because six pots), and that includes most arduino-style boards, and an Arduino Nano or Micro should fit in there easily enough.
Which means the electronics work is mostly just wiring. My version is little more than a bunch of cutting, soldering, taping, and hotsnotting down the Arduino Micro.
You can go a more custom if you want. For example, this project made a PCB you can fasten and plug everything into, like the original board.
There's a number of similar projects and plans you can find around, of course.
The things you want to plan up front
- how to fasten the microcontroller, and how to expose the USB
- you could expose the socket, but I figure it'll break less quickly if you do the socket bit inside so you can tension-relief on the cable
- what you want to output - serial MIDI, USB-MIDI, CV, or such.
- I went for
- serial MIDI because I didn't have a ATmega8U2 style board on hand
- and prepared for (PWM based) CV.
Generic output towards a DAW would probably map each axis to its own CC, so that you can decide on the DAW end what to do with it.
I wanted it to be more of a standalone instrument, so experimented with one side controlling
- which note is being played
- quantizing that to different scales
- pitch bending
and the other side triggering notes pluck-style, or bow-style.
It turns out that imitating motions on a real instrument makes a lot more intuitive sense, though.
TODO: play with the code more and put it on github