As far as I know there is no standard way of supplying power over Midi. My guess is you want to reduce the cable clutter going out the the stage.
If they were going to supply power over the Midi cable, it would likely be done on pins 1 and 3. You could use a multi-meter to test those. I have done this in the past myself.
I have also seen people use 1 and 2, or even 3 and 2, using the shield as the ground for the power. I personally do not like this idea, but who am I to comment on what others do.
If there is no power delivered via any of the above methods, and you have the right expertise, you could modify the POD to deliver power over pins 1 and 3. You would need to make sure of a few things though.
- The cable will need to have conductors for pins 1 and 3. Most (all?) Midi cables do not so you would have to make your own. The best would be a cable with 1 shielded twisted pair and one unshielded twisted pair. Belden used to make such a cable. I no longer remember the part number. The shielded pair would be used or the midi signal, the unshielded pair for the power
- Those pins would need to be unused for anything else by line6
- You would need to be certain you did not create a ground loop. In other words, the power ground and the shield ground need to be connected at only one point in the entire system or not at all
- You would also need to determine if the voltage available in the POD is suitable for use with the Arduino and whether or not the power supply can handle the extra load of whatever Arduino arrangement you intend to use.
- Of course, modifying the POD will void any warranty and will most likely cause line6 to refuse to service it.
Failing your willingness to do that (and I don't blame you) Rocktron make a device (the RDMH900) that uses a 7 pin cable system that can be used to do this for some of their equipment. Check it out here http://www.rocktron.com/products/accessories/midicable5to7pin/
. It would probably be easier to modify that, or build something similar with 5-pin DIN and female power connectors at one end and 5-pin DIN and male power connectors at the other end.
The final suggestion would be to just tape a power extension cable to your midi cable so that they are basically just the one cable.