dirkenstein Posted April 2, 2007 Share Posted April 2, 2007 I'm wondering if somebody has within living memory stuck a 'scope or DMX tester on the DMX output of the strand GSX (125 channels). Is there anything unusual about its DMX timing: MAB, packet rate, or break duration? It's just that I had some problems with one we borrowed end of last year and a self-built DMX to Strand MRL converter, which seems to work fine on both my USB DMX dongles and a Botex DMX tester. It may have been bad cabling or another similar fault but I can't reproduce the problem with anything I have access to. Unfortunately the GSX is at least an hour's drive and a crate of beer away so I can't really justify borrowing it just on the off chance. However, at the moment I'm left with a clever box that I don't trust, and no way to validate the fault. Link to comment Share on other sites More sharing options...
gareth Posted April 2, 2007 Share Posted April 2, 2007 I've never come across any problems. However, if I have a minute tomorrow I'll dig our LBX out and stick a Microscope on the end of it to see what it's pushing out. Link to comment Share on other sites More sharing options...
dirkenstein Posted April 2, 2007 Author Share Posted April 2, 2007 Thanks Gareth- Wasn't quite expecting anybody to go and meter one out for me! I don't actually expect there's anything wrong with the GSXs timing, I was just hoping to set up an accurate as possible simulation of its output in case it makes it easier to provoke the bug. Basically it looks like my DMX receiver code doesn't like short glitches. It inteprets them as breaks, and the remaining trashed packet has its mainly 0 values interpreted as a shorter packet, with all the 0s in the wrong places. Joy. Link to comment Share on other sites More sharing options...
sparkyweb Posted April 2, 2007 Share Posted April 2, 2007 In the dim and distant past I do remember the GSX having timing compatabilty problems with other devices. Sticking a DMX tool between desk and dimmers always seemed to fix it. Link to comment Share on other sites More sharing options...
gareth Posted April 2, 2007 Share Posted April 2, 2007 Thanks Gareth- Wasn't quite expecting anybody to go and meter one out for me!No probs. I'm not promising it'll be tomorrow - even if I do manage to remember, I'm not exactly sure whereabouts in our rather large building the LBX is at the moment. Feel free to remind me in a few days if I haven't responded! Link to comment Share on other sites More sharing options...
AndrewR Posted April 3, 2007 Share Posted April 3, 2007 mmmmm, is it possible that the GSX is outputting at a low rate? Would your converter be affected by that? I ask as I have noticed a number of venues I've toured into in the last month seem to have dimmers that really don't like full-speed output from my laptop (enttec open-usb + chamsys MagicQ, can't recommend it enough!) thankfully there is a 'reduced rate' output setting that solved the flicker I was getting. Link to comment Share on other sites More sharing options...
David Buffham Posted April 3, 2007 Share Posted April 3, 2007 There is something weird about DMX from LBX / GSX. A couple of years ago we were working on a show which was using DB4 Color Block running from a LBX - the DMX completely freaked out the Color Block controller and it wouldn't function at all with the DMX connected. I don't remember the specifics but it was supposedly a known issue due to some non-standard feature of the DMX signal from a LBX. In this case the only option was to use a different lighting console for the show. Link to comment Share on other sites More sharing options...
dirkenstein Posted April 3, 2007 Author Share Posted April 3, 2007 mmmmm, is it possible that the GSX is outputting at a low rate? Would your converter be affected by that? A low rate shouldn't make a difference. The receiver pretty much sticks to spec and and only resets the connection if it sees no data for 1s. It also keeps the scrollers at their last position. It only explicity homes them on actively receiving a 0 or power cycle/watchdog timeout. I did a test with a PIC generating 129-byte DMX frames at near enough maximum rate. (120us break, 12us MAB, back-to-back byte output, and no more than 120us MBB) and this didn't freak out the receiver. Near enough 170packets/s. I even tried 25-byte (minimum length) packets for good measure. I wonder if I've run into a pre-1990 DMX MAB time- single pulse 4us? Or possibly a very short break? I ask as I have noticed a number of venues I've toured into in the last month seem to have dimmers that really don't like full-speed output from my laptop (enttec open-usb + chamsys MagicQ, can't recommend it enough!) thankfully there is a 'reduced rate' output setting that solved the flicker I was getting. Yup that's my toy, too. Enttec USB Pro (not the Open DMX) + MagicQ. Now if I just had the money for a PC wing. I haven't have any problems with that configuration, myself. Any memory of which dimmers particularly get upset? Where is that reduced rate option- part of the MagicQ software or the Enttec libraries? Does it only apply to the basic Open DMX? Link to comment Share on other sites More sharing options...
AndrewR Posted April 4, 2007 Share Posted April 4, 2007 Its a feature of the MagicQ Software, should be supported by any output the desk is using.... Its in setup, settings. Very last last option on the page, several options to choose from. LD90 dimmers I think..... may also have been some RJ Tivoli dimmers. Never made a note Link to comment Share on other sites More sharing options...
gareth Posted April 19, 2007 Share Posted April 19, 2007 Have PM'ed Dirk, but for the info of the general population here's what my MicroScope told me today about the output from our LBX : Time between breaks : 50 mSBreak time : >999 uSMAB : 104 uS In other words, pretty damned sluggish! Link to comment Share on other sites More sharing options...
MarcT Posted May 30, 2007 Share Posted May 30, 2007 Hi Dirk, Yep - the DMX break period of the GSX/LBX is very long. I've had issues getting GSX to talk to early (firmware) BetaPack 2's because of this.As I understand it, its not out of spec - but just longer than some receivers can cope with. There's an (archived) Zero88 technote linked below which briefly mentions this:http://web.archive.org/web/20050216070500/...hnotes.php?id=6 Tom's roped me in for the 16th June, so I can bring a GSX if you want to test this further... Best Regards,Marc Link to comment Share on other sites More sharing options...
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