# MIDI vs RS-232 for show control



## BobHealey (Dec 31, 2011)

I'm in the process of deploying a show control setup for a musical I'm working on. I've got 2 PCs and an ETC Express 48/96. One PC lives up in the light booth and is a laptop coupled to a projector for video. The other is a fairly old first gen Pentium 4 system with a PCI sound card and balanced outputs coupled to the mixing desk.

Ideally, I want to leave the sound FX playback PC with the mixer so that the board op can make use of the other software on the machine (remote interface to the desk, remote meters for the crossover) during the show. This is going to involve a 36 foot or so run of either MIDI cable or serial cabling (either actual RS-232 cable or adapting it to Cat 5E or Cat 6).

I'm using the video system as the master show control machine. Both PCs will be running Show Cue System. Doing testing with all 3 devices next to each other, I've discovered that if I send 2 MIDI packets in a single cue, if I send the one destined for the Express first, the second packet never makes it to the audio PC. Reverse order works every time. MIDI chain is video -> Express -> PC using the Thru port on the Express. Given that minor issue, and the longish run, might I be better off using RS-232 (supported by the software) to link the systems instead of MIDI? I do plan to call ETC on Tuesday to see if this is a known issue. Haven't had too much good luck with their older products and MIDI lately. (Don't even try MSC on Emphasis - if you're lucky, it will just drop packets. If you're unlucky, it will hard lock the face panel).

Thanks for any advice/pointers. I've got a month and a half to figure this out and test, just want to minimize the purchasing of unneeded parts.


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## FMEng (Dec 31, 2011)

In theory, the MIDI should be more reliable over long distances. It is an optically isolated current loop. RS-232 is un-balanced and ground referenced, so it is pretty easy to get ground loop noise on it.

On the other hand, I have run RS-232 a hundred feet or more without problems. If you do run into trouble, one trick that makes it very robust is to use RS-232 to RS-422 converters, which balance the circuits for noise immunity. B & B makes good converters.

Serial Connectivity, Serial Communication, Serial Converters, Serial Cards


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## BobHealey (Dec 31, 2011)

One of the reasons I'm leaning towards RS-232 at this point is the issue I'm having with the Express and not always having MIDI packets relayed out the Thru port.


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## derekleffew (Dec 31, 2011)

But the Express doesn't understand RS-232, or does it?

A 36' cable length is likely not a problem for either protocol, but:
To overcome cable length limitations with RS-232, use a pair of short haul modem. 
To overcome cable length limitations with MIDI, use a pair of MIDI line amplifier.


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## JohnHuntington (Dec 31, 2011)

derekleffew said:


> But the Express doesn't understand RS-232, or does it?
> To overcome cable length limitations with MIDI, use a pair of MIDI line amplifier.



Back 1000 years ago when Derek and I worked together, I used to recommend them but now I would say just run the MIDI line straight through. 

Adding 422 converters (which is what that JL Cooper product is) adds many additional failure points, additional power supplies, etc. My #2 design principle (after safety) is to keep things simple.

Charlie Richmond has run MIDI, IIRC, about 1000 feet on Cat 5. He has more info here. 

John


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## BobHealey (Dec 31, 2011)

Thanks for the insight. It looks like as long as I buy a decent MIDI cable, I shouldn't have any issues electrically. Just need to make sure the Express doesn't drop cues not intended for it and I'll be set. If I had gone with serial between the 2 PCs, the Express still would have been connected via MIDI (its < 3 feet from the video system, so cable length there is a non-issue).


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## SanTai (Jan 6, 2012)

Only curious, but what are you trying to do?


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## BobHealey (Jan 7, 2012)

SanTai said:


> Only curious, but what are you trying to do?



I've got 2 PCs running Show Cue System (http://www.showcuesystems.com) and an ETC Express that I want to control from a single point due to sound op not having sufficient experience to mix and run fx at the same time, and me not having enough hands and arms to trigger lighting cues and video at the same time. I have had some issues with the ETC console eating MIDI Thru packets and not passing them on, so I was pondering if I might be better using RS-232 instead of MIDI to link the 2 PCs since the software also supports that method of communicating with external devices. I'm going with the MIDI at the moment, but I have 90% of the parts to switch to RS-232 if need be.


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## SanTai (Jan 7, 2012)

BobHealey said:


> I've got 2 PCs running Show Cue System (http://www.showcuesystems.com) and an ETC Express that I want to control from a single point due to sound op not having sufficient experience to mix and run fx at the same time, and me not having enough hands and arms to trigger lighting cues and video at the same time. I have had some issues with the ETC console eating MIDI Thru packets and not passing them on, so I was pondering if I might be better using RS-232 instead of MIDI to link the 2 PCs since the software also supports that method of communicating with external devices. I'm going with the MIDI at the moment, but I have 90% of the parts to switch to RS-232 if need be.


 

I was more wondering what effect you are trying to do than what system you are using.


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## BobHealey (Jan 8, 2012)

SanTai said:


> I was more wondering what effect you are trying to do than what system you are using.



I have to run all 3 myself, and I want a common cue stack. Its a staffing issue, not a trying to pull off a nifty effect issue. The musical is Baby, the Sound Designer/mixer op is new and would prefer to concentrate on mixing since he's never done sound outside of his high school before, the person making the background imagery used for several scenes can't make performances, and I'm the show electrician/light op. I wish I was trying to pull off some funky special effects, but just trying to eliminate the need for me to run 3 systems via 3 control surfaces. The still images need to scene transition with the lights too, so using MIDI to sync them is an added bonus.


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