These days, live music performance often involves electronic synthesizers and computers rather than traditional instruments played by hand. To aid in his own performances, [alekappa] built a special interface to take signals from a joystick and convert them to MIDI messages carried over USB.
The build is simple and straightforward, using a Teensy LC to interface with a simple gameport joystick. With a smattering of simple components, it’s easy to read the outputs of the joystick with only a little debounce code needed to ensure the joystick’s buttons are read accurately. Similarly, analog axes are read using the analog-to-digital converters onboard the microcontroller.
This data is then converted into control changes, note triggers and velocity levels and sent out over the Teensy LC’s USB interface. A mode switch enables changes to the system’s behaviour to be quickly made. The device is wrapped up in a convenient housing nabbed from an old Gameport-to-USB converter from many years ago.
It’s a neat project and we’re sure the joystick allows [alekappa] to add a new dimension to his performances on stage. We’ve seen other great MIDI controllers, too, from the knitted keyboard to the impressive Harmonicade. If you’ve got your own mad musical build under construction, don’t hesitate to drop us a line!
The four constant current sinks do look to … constant.
The reference is a 1N4148 (Si SS Diode) and is driving the bases of some BC337 or some old Si transistor like that the different would be at most 0.1V to 0.2V and that across 15k resistor isn’t a lot of current then how much are the junctions (Both Si BJT and diode) going to fluctuate with temperature. Perhaps they fluxgate the same amount ??? as there all Si junctions.
To me it looks like there would be some calibration happening somewhere – perhaps in code.