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RDM Interpretation Questions Discussion and questions relating to interpreting and understanding the E1.20 RDM Standard. |
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September 18th, 2006 | #1 |
Junior Member
Join Date: Sep 2006
Location: Colorado Springs
Posts: 6
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Sub-device response to SET/GET DMX512 start address
Hello all!
I'm working on a device with sub-devices and wonder if anyone can tell me how I should respond to a 'SET DMX512 start address' PID that is sent to a particular device with the sub-device field set to 0xFFFF (SUB_DEVICE_ALL_CALL)? After I set all subdevices to the same address do I respond with 0xFFFF in the sub-device field? Or do I not respond at all since it is an all call? Also, slightly more confusing for me, how do I respond to a GET 'DMX512 Start Address' PID where one device is identified (not a broadcast command) but the sub-device field is loaded with SUB_DEVICE_ALL_CALL? Only one address will fit in the PD for this response but each of my subdevice's addresses could be different. Thanks! Patrick Richart |
September 18th, 2006 | #2 |
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Patrick,
For Question #1: It is expected that messages sent to a SUB_DEVICE_ALL_CALL for a specific UID respond back to the controller. Since you are communicating to a specific UID, there aren't any collision issues that you would have using an ALL_CALL with other root devices. You'll see in the message templates for the Controller and Response messages that 0xFFFF is included in the Sub-Device field as valid for response messages. For Question #2: For a GET sent to all the SUB_DEVICE_ALL_CALL the answer is a little less clear. There is no defined behavior I can think of that specifies a useful response here. It's kind of a non-sensical request to get from a controller for some devices. Some options you have:
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Scott M. Blair RDM Protocol Forums Admin |
September 29th, 2006 | #3 |
Task Group Member
Join Date: Jun 2006
Posts: 181
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Patrick
For Question #2 I favour Scotts third option - use of the NACK with NR_SUB_DEVICE_OUT_OF_RANGE |
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