BenHowitt Posted June 17, 2008 Share Posted June 17, 2008 So yeah. I'm aware that I started a similar topic, which was soon (and rightly) shot down in flames. I apologise in advance for any confusion that might occur as a result of this. Basically, could anyone explain the form in which a normal DMX signal takes place. I'm assuming that it would be DMX address (0-511) followed by the relative value (0-255) but if I'm wrong, please tell me. If I can explain, I'm trying to make a DMX controlled strobe adaptor for a light and, to save money, would like to make the decoder myself. If I am, as I suspect, completely confused and incoherent, could someone point me in the right direciton for a DMX decoder. An example: if I wanted to set DMX address 008 to 255, what form would the signal take? 000001000 11111111 ? Thanks, Ben Howitt EDIT to correct spelling and to add example Link to comment Share on other sites More sharing options...
smalljoshua Posted June 17, 2008 Share Posted June 17, 2008 This Page could come in handy http://www.dmx512-online.com/ Josh Link to comment Share on other sites More sharing options...
BenHowitt Posted June 17, 2008 Author Share Posted June 17, 2008 Thank you Josh. Looking at that stupid complexity, I think I might get an automatic decoder. Anyone have any suggestions? Link to comment Share on other sites More sharing options...
david.elsbury Posted June 17, 2008 Share Posted June 17, 2008 DMX is basically RS-485. There are numerous RS-485 chips around, so do some more research into that area. Link to comment Share on other sites More sharing options...
jakefraser Posted June 17, 2008 Share Posted June 17, 2008 Have a search for 'DMX circuit' or similar on BR - you'll find there are some useful discussions on their use. One that you may find particularly handy is this from dmxprojects.com, but you do have to be quite handy with a soldering iron... HTH Link to comment Share on other sites More sharing options...
Brian Posted June 17, 2008 Share Posted June 17, 2008 ...stupid complexity...Actually you should have written 'stupid simplicity'. DMX was designed before the days of cheap micros and so was meant to be decoded with pure logic attached to a UART. Link to comment Share on other sites More sharing options...
Jivemaster Posted June 17, 2008 Share Posted June 17, 2008 DMX actually transmits a frame of up to 512 data Bytes of 8 bits. so there are timings to check then frame starts to find then the value at the nth byte is the value sent as the value of n There is no need to send data after the last device number and some cheap controllers only sent 128 or 256 channels. Others can send all 512 several times called universes DMX runs at about 250 K baud which is similar to 250 KHz Hence all the chat about getting the wires right. Link to comment Share on other sites More sharing options...
KevinE Posted June 17, 2008 Share Posted June 17, 2008 This is because no addresses are actually sent, only the data, the address is done by a counter in each fixture. Link to comment Share on other sites More sharing options...
boatman Posted June 17, 2008 Share Posted June 17, 2008 Thank you Josh. Looking at that stupid complexity, I think I might get an automatic decoder. Anyone have any suggestions? As others have said DMX is a very basic protocol and not at all difficult to understand. However, what you have to do is define the required outputs from your decoder to control the strobe; then go here and pick the correct board that will provide those signals for you. Link to comment Share on other sites More sharing options...
BenHowitt Posted June 18, 2008 Author Share Posted June 18, 2008 OK. Thanks for all the help, guys. I think I understand now. Ben Howitt Link to comment Share on other sites More sharing options...
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