Jan 172012


Strand Console - Stock Photo

In early December, we were contacted by a company which specialized in automation & systems integration.  One of their clients had a large museum / interactive type exhibit based on some older AMX / Crestron technology.  These guys were tasked with modernizing the entire system, adding more sophisticated and flexible lighting, and changing the way the audience interacted with different elements of the display.

Their requirements looked something like this:

  • We have a DMX console which needs to drive ~ 150 channels of moving light and LED fixtures at the beginning of the show.
  • Also, there are existing (and installed) relay cards which must still be driven at the same time, but these cards only accept input from the AMX system.
  • The current AMX system is handling the touchscreens, video playback, audio and more.  So it definitely stays as part of the new installation.
  • Finally, at the end of the show, the system must switch from ‘canned’ to interactive operation.  Input from a large touchscreen needs to direct the moving lights, the LED fixtures and all the low-voltage relays such that many different scenes can be displayed, but in a random order.

With some careful planning, we developed a version of super-turbo bidirectional DMX / RS232 bridging firmware for the DecaBox which exactly matched the needs of the project.  It included the following features:

Switchable External / Internal DMX Output The DecaBox contains ports for DMX receive, passthrough and transmit.  Receive and passthrough, of course, are connected in parallel with each other and with an input on our internal processor.  Transmit is connected to an output on our internal processor. By means of a simple RS232 command, the AMX brain could direct the DecaBox to either (a) retransmit incoming DMX from the upstreaming lighting console or (b) generate DMX scenes internally, ignoring upstream data.

DMX to RS-232 Parsing. This of course is how we were able to use the DMX lighting console to drive the AMX-only relay cards.  Since we didn’t know a priori how many DMX channels were required, a simple text file stored on the DecaBox’s internal SD memory card allowed for field programming:

baud 19200 ; can be changed to any standard baud rate

; beginning DMX channel to be monitored

start 100

; last channel to be monitored

end 242

As DMX data was received, the channel range called out in this text file was monitored carefully.  Each time  a DMX channel in this range changed its value, a short serial string was transmitted the AMX system:

100 @ 004

100 @ 005

100 @ 008

100 @ 010


In this way, the AMX brain could keep an eye on the incoming serial data.  When the proper DMX channels reached appropriate levels (usually FF, but anything is possible), the AMX system set the relay cards to the proper state.  With this firmware addition, the DMX console could drive the legacy relay cards properly.

RS232 Triggered Scene Recall Finally, for the interactive section of the show, the designers wanted a series of different lighting looks, based on which section of the touchscreen was triggered.  Though the DecaBox has an internal DMX Scene Engine, the AMX programmers didn’t want to build lighting scenes channel by channel.  It was much easier to use the external console, with it’s intelligent-light-specific programming tools, to design the required looks.

So, we added a ‘snapshot’ ability to our firmware.  With valid DMX connected to the DecaBox’s input and the downstream moving lights and LEDs connected to the output, the users could use the three front panel pushbuttons and LCD to capture static DMX scenes.  These scenes were stored safely on the memory card, and can be recalled using a very simple RS232 syntax, complete with crossfade times.

Thus, the show could start under control of the large DMX console, with the DecaBox providing RS232 translation of the required channels for relays and low voltage equipment.  Then, the AMX system could toggle between live and captured DMX data during the interactive portion of the show.  The pre-built DMX scenes could be generated and faded between as randomly required, based on touchscreen input.

All in all, this was a fun project to work on.    At last check, the equipment was all running well.  We’re thrilled that the DecaBox offers such a flexible and powerful platform.

If you need something similar (or even something wildly different), please let us know.


 Posted by at 8:19 pm

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