Sunday, May 20, 2012

Quick Hack

Makers Faire was this weekend and for once I didn't have to work a show.  I went, I wandered, I bought a couple parts, but mostly I listened to music, pedaled a generator at the pedal-powered stage, and drank the only beer they sold (although I was dying for some decent German beer).

Was house tech over the weekend for a show that brings their own sound and light operators.  Except for one early-morning showcase performance.  When they handed me a CD and told me they had a couple of simple lighting cues.  Problem; the sound board is still at FOH position (actually, rear of the house, but the important part is, it is NOT near the light board).

So pulled some toys out of the bag to be able to run the light board remotely.  There's one MacGuyver episode where he has to build a telescope from random lenses and he has maybe five minutes to do what took Galileo years.  But as Mac puts it -- he already knew it could be done.  Same with the lighting console -- I'd SEEN another group use one of the MIDI functions to control the ETC "Expression" board.  I just hadn't done it myself.

Opened the manual.  The Expression speaks MSC (MIDI Show Control) and will take a "Go" in that format.  Ran a MIDI connection through the audio snake that was already there via my hand-made pair of MIDI-to-XLR adapter cables.  I remembered QLab had some kind of drop-down menu of MIDI control sequences already written for you -- I opened up my fully-registered copy of QLab 1.0 and looked around.

The board didn't seem to be seeing the commands, but then after I'd tapped at the button a few times (trying different options) I noticed the lights had changed.  Turns out you had to deliberately press and hold the "send a message now" button within the QLab interface before it would spit out the full-length MSC.

Now, since it was already in my bag, I pulled out my Arduino-based MIDI message generator and the XBee-modified Staple's Easy Button.  And now I could trigger the "Go" button for the next lighting cue from basically anywhere in the theater.



It's a hack, and a bit of a chain; the inside of the Easy Button currently holds not just the XBee node but is wasting a perfectly good USB Explorer as a break-out board.  I haven't gotten around to putting in a new breakout board (and boost converter) as replacements.  When the Easy Button is pressed, the XBee node sends a radio message with the changed status of pin D0.  The receiving node toggles the output level of its pin D0 in response, and the Arduino it is connected to detects this as a switch closed (aka +v is present on a pin that is otherwise pulled to ground.  Or is it the other way around?)  The Arduino, which at least is in a nice box, debounces the "switch/sensor" input, creates a NoteOn event, and sends it out the serial port at 31250 BAUD.  A standard MIDI connector picks this up, creates a newly formatted message via USB, and this triggers a cue within QLab.  The QLab cue creates a new MIDI event -- an MSC "Go" command -- and shoots that OUT the same USB MIDI adapter.  That runs through two adapter cables and sixty feet of audio snake to reach the back of the lighting console.

But, the point of the demonstration is, this worked.  And more importantly than that, it worked off-the-shelf.  I had the components already, and I didn't even have to go inside via the USB connection and write new code to one or more of the components to do this particular task (which, if I had, could have removed the laptop and its MIDI adapter from the chain of connections).

And this is what I've been striving at with all of my theatrical gadgets; to have things that I can pull out of the gig bag and hook up in a few minutes to solve a problem.  Or to so something new that hasn't been done before, thus enhancing the fun and the creative options of a show.


And today I needed to do a touch-up focus on stage and I had no assistant to run the board.  At least this theater has an RFU (Remote Focus Unit), but it was still faster to write a couple of cues, each containing just the system I needed to touch up, then hook up my Wireless Easy Button again.  And then I could move from light to light without having to run back to the board each time.




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