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Old November 19th, 2010   #2
Join Date: Feb 2006
Posts: 430
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Good question! Section 3.1.2 specifies the timing values for packet spacing between Null Start Code frames and RDM frames as well as RDM Discovery frames. These timings are the only requirements in how you handle interleaving between the packets.

As long as you follow these requirements you are then free to interleave in whatever makes the most sense for your product.

In general, a number of products will do a 1-1 interleave of DMX NSC, RDM Request/RDM Response, DMX NSC. With that type of 1-1 interleave you can still maintain about 26HZ refresh rate of the NSC packets.

There are many tricks and optimizations you can do based on your application and need. For example, if you are in the middle of doing an active crossfade, you may choose to reduce or eliminate the frequency you send RDM messages in the background in order to maintain a higher refresh rate during the crossfade.

At the same time, if you are doing something more intensive with RDM and your DMX values aren't changing then you can dramatically throttle back the number of DMX NSC packets you are sending and mostly just send RDM packets. Your only real requirement is to send an NSC packet at least 1/second to keep the signal alive so the devices don't go into a "loss of signal" scenario. The rest of the messages could all be RDM traffic at that point.

Hope this helps shine some light on it for you.

Scott M. Blair
RDM Protocol Forums Admin
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