How should a device with footprint=0 respond to setting the DMX start address?

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Originally Posted by mikemac

Why a NACK and not an ACK? Since the footprint is zero, the device isn't going to use any slots so it really shouldn't matter what the DMX address is set to. I would think returning a NACK to a controller could confuse it as it thinks it is sending a valid request.

Mike, welcome to the forums!

There's two issues here. If the Footprint is zero then that means the Start Address PID is probably not a supported PID. The language in the current version of RDM creates some confusion here because the Start Address PID isn't one that is supposed to be sent in a SUPPORTED_PARAMETERS but it is also allowed not required if it doesn't have a footprint.

The other scenario is that the general view is that a device shouldn't ACK something unless the action has been completed. If you send a SET and it didn't actually do the set then that should be a NACK. If it allows you to actually change the address for use with other personalities that do have a non-zero footprint, then I agree that would be an ACK.