GPIO input module question / bounty for rPi

Scott Wegner · Sat May 24, 2014 2:56 pm

Hi all,

I'm tinkering with QLC+ on a Raspberry Pi and so far I'm reasonably optimistic. I've got some basics compiled and working and I think for my application, there is potential.

One of the pieces to the puzzle I have is this: I'd like the ability to trigger things in QLC+ via simple buttons. There are already a number of ways to do that by using MIDI in and various midi controllers. My favorite so far is to use an Arduino as a simple MIDI controller and feed that into the pi directly with a simple MIDI/USB adapter.

However, it seems kind of silly to do that when there are a bunch of GPIO pins on the pi already, just itching be be used as simple triggers. Using the GPIO pins on the pi would eliminate lots of extra hardware, which for the application I have in mind would be very good.

So here is my question(s): Has anyone triggered QLC+ events with the rPi GPIO pins, and if yes - how did they do it? If not, is there anyone out there who would be willing to write a module that would 'watch' the GPIO pins? Would a 'bounty' be appropriate? I have ZERO code skills and am more of a hardware hacker, so there is no way I could do it. I realize that this is such a niche use, and I understand that this would be VERY low on the communities' TODO list, hence the suggestion that I put up some kind of bounty - or hire someone outright to code it.

Lastly, assuming I'm going to mount this all in a stomp-box of sorts with 4 or 5 buttons on the top for foot control - is there an input method that I'm missing? Like I said - keeping hardware to a minimum would be nice. I suppose I could use the HID module and rip apart a keyboard and hack together a USB input triggered on 4 different keystrokes. I have not even looked into the HID module, so I don't know if that is even an option.

Thoughts?

Thanks!

Scott

Massimo Callegari · Sat May 24, 2014 4:07 pm

Hello Scott, at the moment I'm not willing to implement such functionality.
As you said, it's a very niche application.

What I suggest is to find a cheap USB device recognized by QLC+ and tweak it to work as you have in mind.
I'm thinking of a $5 USB keyboard...for example.
No need for MIDI, Arduino and GPIOs.

Chris Laurie · Sun May 25, 2014 4:33 am

I have had good success with this [device from Leo Bodnar](http://www.leobodnar.com/shop/index.php ... cts_id=204) It can do up to 12 buttons when wired simply and up to 36 when wired in a button matrix. While the device can drive 8 sliders, on Windows, QLC+ can currently only use 6.

I also have one of [these Teensy boards](https://www.pjrc.com/store/teensy31.html). The beauty of this board is that with a simple software change it can be either a MIDI device or a joystick. I have yet to build something with it but my initial playing with it, is very promising. You have to tweak/write the software yourself though.

Scott Wegner · Tue May 27, 2014 10:54 pm

Wow - thanks guys! That makes a ton of sense. A while after I posted my question I started to come to a similar conclusion. As elegant as GPIO access would be... in the long run just working with "knowns" will be a better solution - just as you both suggested.

Thanks again!

Scott