The Line 6 Pedal Board will now receive an Arduino to replace its main board. The goal is to attach this Arduino to a computer using midi on a USB connector.
For testing purposes, I will use an Arduino Duemilanove that I have on hand.
I will use an Arduino sketch to test the midi-to-USB communication. The program has been tested in that post.
I purchased a Midi-USB adapter on eBay for 4.50$. There are plenty available, and only a few models to chose from. The one I got has a decent USB chip and does include an opto-isolator on the midi IN port (not all of them do!). I could have used the M-Audio Uno that I already have, but I need it later in the project.
One end is USB and the other end is connected to a pair of midi cables. I started by removing the midi cables, but I kept stubs attached to the plug. A little modification will let me get phantom power to the Arduino from the USB port. Let’s take a closer look at that board: (click on it!)
On the left side, the pins are going to the midi cables, from the top;
- I-; Midi IN
- I+; Midi IN. Both pins go into the opto-isolator (IC to the right of the diode)
- O-; Midi OUT
- O+; Midi OUT
On the right side, the pins are going to the USB cable. From the top;
- Vcc (5 volt)
Trying it with the Arduino: It works!
Here’s a schematic for the modified circuit
I soldered everything and used heat shrink tubing. Tied the grounds together to use only one resistor.
A cleaner look!
Everything back in the box, to protect the circuit and the wires: