Strand Lighting "ShowChanger" Data Protocol

[cman517]

I'm looking for anyone with any knowledge of the data transmission protocol used by the Strand ShowChanger components.

 

We have a collection of color scrollers that appear to be Strand parscan units and all I can find online is that these communicate via a Strand protocol known only as ShowChanger. These scrollers have the 9-pin showchanger port on them, and we have a power supply / brain unit (what I am assuming is the "AutoScroll") and a premade DMX converter that doesn't appear to be working. The converter was acquired with virtually no information as to how it works or what is wrong with it, though looking at it I can say that it appears to be built on the PCM4862 platform.

 

Anyway, we've virtually given up on trying to fix or get this converter working. What were trying to do now is understand this data protocol and program an Arduino or something similar to receive a DMX singal and process it into this other kind of Strand signal. THis is only going to be used for the color scrollers. We've found the user manuals for the scrollers, the "Taskmaster" (the board used to control them from the time) and the "Autoscroll", the brain for the units. The manuals include some preliminary information as to how the protocol works, but it certainly doesn't have everything.

 

If anyone knows anything about this system and how it works, any help would be much appreciated. Below is a link to the autoscroll manual that includes the most information as to what this protocol is.

 

http://www.theatrecrafts.com/archive/documents/autoscroll_operation_manual.pdf

 

Thanks.

[DrV]

Can't offer any informed insight but isn't the table on page 41 (48) enough? The way I read it is they are 8 byte frames of data which could be used by various different types of fixture but a scroller would only need to look at the colour byte. There's a fixed header sequence of 0xFF, 0xFF, 0xAD (sort of equivalent to the DMX break) followed by 100 data frames, the last one being all zero bytes. All sent at 62.5 kBaud using RS485. (i.e. much slower than DMX). A whole transmission is 803 bytes so the refresh rate is less than 7 per second. It looks as though the only additional information you would need is the relationship between the value of the colour byte and the distance along the gelstring and that could be determined by experiment.

 

One slightly tricky thing for an Arduino might be simultaneous transmit and receive at two different baud rates so you would need to use one with more than one serial port, or perhaps just switch to the output baud rate when you need to send a packet to the scrollers.

 

The way I'd tackle this is initially to program an Arduino to output a valid sequence of a header, 99 frames of mostly zeroes including a few frames with some different colour values plus the all zeroes final frame. That would be enough to check that the scrollers responded before embarking on writing the whole thing. I assume the scrollers have a switch to change their address (1-99)?

 

Dave

[theatretechie]

Hi,

 

Maybe I can help.

 

I don't fully understand the protocol etc. But I do know that Flying Pig (back in the day) created a DMX to Strand Protocol Converter.

 

This box was used inline to Strand Pals, Parscans etc with a DMX console.

 

Have a look at this thread and tell me if its similar what you have. There is also a picture of the Flying Pig Protocol converter box.

 

http://www.blue-room.org.uk/index.php?showtopic=43343

 

I know these boxes are as rare as rocking horse poop! BUT, I have one somewhere. I was tempted to buy the Pals kit from 10 out of 10 for a bit of a play around. But that has never taken off due to my touring schedule.

 

Let me know if its what you need.

 

Jon