You need the green and black wire and then trim the red down the way the green one was trimmed down. It needs to be long enough to reach the circuit board. then you have to cut the wires that go into the midi usb device and then using a pair of pliers you need to draw the whole cable through about 3/4 of an inch because you need to get the hidden green wire thats been trimmed at the factory. You can try this modification yourself but it does require a little nerve (and a good eye) as you have to trim and solder the optisolator into place and also getting the resistor pins bent just right and making sure the leads don’t touch any other components. You get what you pay for: some self assembly may be required. This USB MIDI cable might be a cheap and quick way to add USB enabled MIDI for Arduino, but I’m really wondering if it would have worked with any MIDI device at all due to incorrect wiring. The case fit back perfectly, though required some glue to hold in place and MIDI-OX finally came to life! Soldered the green DIN connector wire to IN+ pad.Soldered the black DIN connector wire to IN- pad.Removed the red DIN connector wire completely from GND connection and trimmed it. I only had to shorten the pins to mount it as close to the board as possible. Soldered opto-coupler in U1 and it was a perfect fit for the pinout.A quick assembly on the breadboard and a bit of soldering for ground, 5V and data lines to get to this:Īnd it worked! It was finally time to populate the missing components: So, I went to Maplin and purchased a low-current opto-coupler SFH618-2 for £1.39. Rock Band keyboard probably was not expecting this. The USB cable did not have these parts populated and used a common ground for signal transfers. The MIDI specification requires an opto-isolator to completely isolate MIDI connected circuits. Here is a very rough schematic of how it’s done and how it should have been done: After further investigations, it turned out that the wiring was done completely different to the MIDI specifications. That’s when I decided to open up the plastic casing to find a few surprises…įirst thing I noticed, were the missing components on the board pictured in the red square. The Rock Band keyboard detected a MIDI cable and switched to MIDI mode, PC properly detected USB MIDI device, but there were no messages in the MIDI-OX application. Videos online demonstrated that connecting the IN connector to the keyboard and USB cable to the PC was all that was needed to use it, but I just couldn’t get it working. I had recently bought a Rock Band 3 Wii keyboard which has come down in price to around £10 with an intention to connect it to a cheap Chinese USB to MIDI interface cable for around £3 pictured above to do some MIDI experiments on my computer.
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