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

[sblair]

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.

[peternewman]

I'm just going to echo part of my earlier post:

Originally Posted by peternewman

To me, NR_DATA_OUT_OF_RANGE sounds ideal, from the RDM standard description "Value for given Parameter out of allowable range or not supported.".

The asymmetry there is no different to almost every other PID.

Originally Posted by sblair

The other scenario is that the general view is that a device shouldn't ACK something unless the action has been completed.

Devil's advocate, should it ACK a SET of 0xFFFF?