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For our next school theater production the director has asked me to come up with a solution to show some simple graphics on a computer screen. My first idea was to simply connect a (very) long VGA cable to my computer and control it from there. This would however cause a lot of problems.

My next idea was to use a Raspberry Pi to show the graphics on the computer screen and control the Pi from the control booth. It would be pretty easy to use Ethernet or connect a long cable to the GPIO pins, but since we are already using DMX to control the lights, it would be great if we could use the same to control the Pi.

So my question is: how can software on a Raspberry Pi listen to a couple of DMX channels and take appropriate action? Existing solutions I have seen so far use a Pi to control lights using DMX, but I'm looking for the opposite.

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    I think it should be possible to do so. After all it is "just" a serial bus, electrically based on RS-485 differential signaling and a quite low data transfer rate.
    – Ghanima
    Oct 11 '14 at 13:45
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    A problem with DMX is the two stop bits. I'm not sure if the standard Raspberry Pi Linux serial drivers can cope with that. Also 250kbps isn't a standard speed, but for that there are simple workarounds. It may be simplest to buy a USB DMX512 dongle. Mind you it's far simpler just to use Ethernet.
    – joan
    Oct 11 '14 at 14:06
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    RS485-to-USB converters are available up to 250 kbaud. Ethernet or maybe even WiFi sound simpler, sure, but the project also has a certain ring to it :)
    – Ghanima
    Oct 11 '14 at 14:08
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DMX controlled 'light'-switches are readily available. Connect the output to a GPIO pin and read the status.

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