I’ve built several MIDI based devices using the Arduino microprocessor – recently I found an article online about hacking this $6 USB MIDI cable (see update below) to provide hardware MIDI over USB.
When my cables arrived I noticed that they were a different revision number to the one described in this article. Once I figured out the modification for this board version I thought it was worth posting.
All you need to do is desolder the top white wire from the MIDI side, and hook this to the 5v supply coming from the USB side, this now provides power to the Arduino device. Next connect a 220 Ohm resistor from the same 5v power terminal to the terminal that the white wire was originally connected to. That’s it.
Just remember to set your baud rate in the Arduino sketch to 31250 and everything should work OK. The blue indicator light on the USB cable interface should flash when MIDI data is received.
The USB cable declares itself to Windows as a MIDI device, no driver needed, and the Arduino is powered from the the white (5v), black (TX) and red (GND) wires coming from the left hand side of the board.