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Old February 15th, 2015   #2
ericthegeek
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Join Date: Aug 2008
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Quote:
Originally Posted by dannito View Post
1. During discovery. Whenever it sees the first preamble 0xFE it must turn all the transceivers to receiver mode.
You need to turn all of the transceivers into receive mode at the end of the Discover Unique Branch request (within 176us after the second stop bit of the last byte). This will allow your inline device to hear the DUB Response no matter what port it occurs on.

Quote:
Originally Posted by dannito View Post
1.1 Listening to each Command port, and soon as one of them is pulled to LOW state it must route its data to responders PORT so the console could receive it. As well as to "mute" the rest of the Command ports during its data delivering (?).
OR
1.2. Just route all the data received from each Command port to Responder Port?
(Is it 1.1 or 1.2 ?)
There's no required behavior, either behavior is valid. But, you do need to consider that the device being discovered may be attached to the responder port, not just to the inline device's downstream command ports.

A common mistake is to simply AND together all of the command ports and drive the resulting waveform back to the responder port during the discovery response period. This works if all of your fixtures are on the "outputs" of the splitter, but will create bus conflicts if there are other fixtures on the "input" port.

Quote:
Originally Posted by dannito View Post
2.0. The time period for the port turning is 5.8mS? Then it switches back to normal forward data flow.
The 5.8ms discovery response period includes time for transmission delays, as well as 200us of extra margin, and is officially only valid at the controller.

For inline devices it can be a bit harder to determine what value to use. You'll want to use a value somewhere between 2.9ms (DUB response delay + Max packet time) and 5.8ms. I think I use 5.6ms in my implementations.

Quote:
Originally Posted by dannito View Post
3.0. During non-Discovery mode, after receiving an RDM request packet, the first port that is pulled to a LOW state for the start of a BREAK becomes the active port. If the Port which is pulled LOW is Responder port, the In-line device must return to normal data flow mode. If this port is not Responder, it must send its data to:
3.1 Only to Responder?
3.2 Every other ports on the device?
Again, either behavior is valid. Personally I prefer to send it to all ports on the device because it allows you to connect a sniffer to any port in the splitter, which can make for easier troubleshooting.

Quote:
Originally Posted by dannito View Post
Please accept my apologies, but I am new to this and it's all I can understand reading the standard.
No need to apologize. You're asking good, solid technical questions, which is exactly why this forum exists.
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