Point a newbie toward midi design
« on: April 28, 2015, 04:08:24 PM »
I have some analog experience  (mostly dealing with guitar electronics), and would like to learn about midi interfaces for guitar. I would be interested in something like a harp guitar, with 30 or more (piezo) string signals to USB out; , maybe even midi coming in to trigger actuators or motors.  I'd really appreciate it if someone could point me toward design principles, and maybe some info about chips, boards and programming software that folks like to use .  Thanks much  --  Mark


Re: Point a newbie toward midi design
« Reply #1 on: April 28, 2015, 04:21:30 PM »
That's a big project I guess, sensing the strings is a big deal, the strings which are always open is not a big problem since you only need to see if they are playing and maybe the sensitivity, so note on message and level, not a problem, takes no time. The problem is with the other strings, when they may be different notes, so you need to detect that note. I don't know the actual processing normally used to do that but it must be fast and is not easy to detect a note from the first few ms of it. You will need a good processing power to do that as well. Once you have the data you need to transfer via MIDI is pretty straight forward, a small arduino could do that. A bigger Arduino could do that plus the actuators and trigger management. The problem is the other part, you need 6 decent AD converter for each string plus one simpler AD for each open string to sense the level.

I don't know the usual hardware and software for each task, I guess a decent processor and a micro controller could manage all that stuff, raspberry pi, arduino, pic, comes to mind. There is a mixed arduino board which may do both things but you probably run out of pins pretty quickly from it, using a bigger arduino like a mega or so plus a raspberry is probably a better bet.

If I don't know how it works, I prefer don't turn it on.