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RDM General Implementation Discussion General Discussion and questions relating to implementing RDM in a product.

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Old September 30th, 2009   #1
mike_k
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Default Figure 7-2: Device Discovery Process

Some time ago I noticed that this flowchart may lead to some problems if people use it as an implementation guide...

The flow chart does not handle ghosted UIDs very well.

For instance:
The flowchart says that if you get a single response and then no response on MUTE of that UID, then the current search interval is terminated.
Hence, if you get a ghosted UID due to collisions and the ghosted UID does not exist in the network, then it will not branch any further.
If I remember correctly this is handled in the pseudo code in the appendix (don't have the document right now), but I think it is quite serious if this is not noted in the discovery section flow chart (or at least as a note).

Also, the case with a ghosted UID of a device that is actually on the network is not handled since if implemented as the flowchart describes it it will get stuck in an endless loop. (As the some controllers seems to do.)

I guess the flowchart is intended just to give a basic idea of the binary search tree, but since we have seen controllers having problems with ghosted UIDs, then it might be necesarry to actually give this issue more space and focus.
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Old October 1st, 2009   #2
sblair
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Michael,

I take your point. It's tough building an understandable flowchart that encompasses everything. At the time this was created we had not encountered that scenario. When I wrote the pseudocode I had tried making it as bullet-proof of an implementation as possible.

We should be able to add something in the next round of errata to at least highlight this issue with the flowchart.
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Old October 1st, 2009   #3
mike_k
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Fair enough. I'm comfortable with just adding a note pointing the issue out and explaining that the flow chart isn't intended to be complete, but rather give an introduction to the concept.
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