2007-04-01T00:38:58 theater lighting test: Got an enttec opendmx box, which works great with these instructions. The dmx4linux project claims to support opendmx, but I couldn't get it to build easily on a modern kernel. I only had a little time in a real theater today, so I borrowed an oscilloscope to see if I was even getting any DMX output at all.
That's a successful test of turning some channel from 0 to 255. You can see the bits in that byte getting set over the four photos. (Lower voltage means 'set' here)
I actually debugged some python/pyrex code with the oscilloscope. I was testing multiple channels and at first, only the first channel seemed to work. Or, only the first N channels worked if they were all nonzero. It turned out that I was using a strncpy somewhere on the DMX output packet, which was stopping at the first null byte. I didn't need a scope to find that bug, but I happened to be watching the output with one already.
In the theater, the opendmx worked perfectly. Audio from the laptop to the theater sound system also worked perfectly. This should be a very nice show if I don't have to spend any time debugging flickering lights and humming audio.
Meanwhile, I seem not to be the only one doing theater lighting with python and twisted.
