Hooking up a LED feedback indicator to megadrum?

[mbira]

Hi guys,
Now that I have successfully completed the 32 channel megadrum, I'm on to the next step:

I am using the megadrum in my band as a midi trigger for 31 separate triggers that can trigger samples from within Ableton (the triggers are spread across the stage and played by various members).

Ableton has a midi feedback feature where when a note is triggered, the feedback will send midi note information.

I am wanting to build 31 LEDS that will be connected to the trigger pads so when a person hits the pad they get a visual indication that everything did indeed work correctly. Before I found the megadrum, I was looking into doing this with an arduino, but now I'm wondering if there is a way to combine the megadrum so I wouldn't need a separate usb input from the computer into the arduino...IE is there a way to take those incoming feedback messages straight from the megadrum and feed an arduino?

Or is there a better way to do this that I haven't though of?

Cheers,
Joel

[Rubis]

There is a thread on the Vdrums.com forums about this: http://vdrums.com/forum/showthread.php?t=47768

I just linked the first page. Most of the good stuff start near the end.

[mbira]

Yeah, I've seen that link. That technique is taking the signal of the hit pad before it goes into a computer or anything...I need something that reads the midi feedback from the computer. This is to avoid any possible false readings (IE the light goes off because the pad was hit, but the clip still didn't trigger...)

[Rubis]

One of the last few pages had some stuff about the Midiuino, which basically does what you are looking for. The code would probably work for other arduino devices as well with little to no tweaking. Arduinos can run on batteries too. I don't know if MD has enough power left over to run another device or not, but if it does, that may be a solution as well.

[mbira]

Thanks for the update-I'll admit I hadn't checked out the end of that thread. In the meantime, I had posted a message at the Arduino Forum. You can read that here:
http://www.arduino.cc/cgi-bin/yabb2/YaB ... 400060/0#4

The short answer is that there is a driver chip-the MAX7221 that can feed many LEDs from a standard arduino. I've got the max samples ordered...Looks like I'll need a second USB cable going into the machine anyway to power the LEDS so I think (hope!) I can just use midi yoke to send those feedback signals straight to the arduino.

[davem]

I've been following this and I'm quite interested in the idea myself. To avoid the second USB cable, could you use a passive USB hub inside the enclosure? I'm guessing it really depends on how many mA MegaDrum draws off of your USB ports (I have no idea as to the answer).

[mbira]

Well I'll be running 32 LEDs, so I need the separate USB to power the arduino board and leds. Plus I'd need a way to get the midi feedback signal in to the arduino anyway (I am only using usb). Hopefully I'll get everything by next week, so I'll keep you posted.

They talk more about the current draw here:
http://www.arduino.cc/playground/Main/MAX72XXHardware

[mbira]

Here's an update:

I ended up purchasing an Arduino Duemlenove. It cost about $30. THey have a singlesided home-etch version, but it doesn't have a usb connector, so I opted to buy instead of DIY.

There is a "serial to midi converter" that is a software solution that someone created. You can install that, and then just read midi via the usb cable into the arduino.

I was sure from talking with people that I'd easily get 32 channels of LEDs going by using the MAX7221 chip to drive half of an 8x8 LED matrix.

Well after a couple weeks of fighting the code to get my elaborate plans working, I discovered that because the max is multiplexing that I'd probably run into a lot of trouble with EMI on stage with a few 20' cable runs going into the arduino from the triggers. I decided to go for a constant current solution, and so right now I have seven channels (one bank because I'm iusing a VGA cable-15 pins). Those seven channels are lighting leds independantly for the trigger hits, and working well at this point. When I decide to add more, I can just add them in banks of 7 (or more if I want to deal with making my db9 cutouts fit db25 plugs.

For now I am happy and content!

So basically, I have a 1U rack unit with a 32 channel megadrum on one side, and an arduino on the other side. one usb goes to the max, and one usb goes to the arduino.