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Old September 18th, 2006   #2
Join Date: Feb 2006
Posts: 432
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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:
  • If you have determined that all your devices in fact have the same value for all sub-devices you could respond with the actual data value with the SUB_DEVICE_ALL_CALL.
  • You could Queue up messages for ALL the Sub-devices and return them one at a time with the QUEUED_MESSAGE request. Could be a bit messy though.
  • Probably the safest thing I can think of would be to NACK it with NR_SUB_DEVICE_OUT_OF_RANGE, that way there is no confusion about what you're going to do with that GET request for all the sub-devices.
Scott M. Blair
RDM Protocol Forums Admin
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