pic dmx interface software


Posted on Feb 6, 2014

The idea for the project started nearly two years ago, while I was researching the purchase of a new lighting board for a small theatre where I was working at the time. While our old board was nearly twenty years old, and desperately in need of a replacement, the costs of purchasing any new equipment from Strand, or other brand name providers, end


pic dmx interface software
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ed up being so prohibitively high that we were forced to abandon the idea of new equipment entirely. Around this time I began looking into computer-based lighting consoles, which a few DIY-ers had pieced together, and posted some limited information on the internet. See this product from ENTTEC. There are several more systems, too, all essentially based on a serial interface to the computer, in which signal-level data from either the parallel port, serial port, or USB is converted into RS-485-signal-level data by a chip, and sent down the line to the dimmer. Essentially the computer broadcasts a DMX signal, which then gets a slight voltage boost, and sent down to the dimmer. I set out, around that time, to build my own system based on the DMX Dongle schematics. I quickly realized a major flaw with all of these systems. The DMX specification requires the light data to be continuously refreshed to the dimmers, at about 44Hz. This means that a full 512 channel packet it sent from the computer to the dimmer 44 times per second. A gap in this stream longer than half a second could cause a flicker of the lights, which is not an option when running lighting for any type of performance. However, most of these systems were using the computer to broadcast the DMX packet, meaning that if, for whatever reason, the computer should freeze up for even half a second, the flow of transmission would be interrupted. For this reason, I decided...




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