View Single Post
Old July 10th, 2009   #1
Junior Member
Join Date: Jul 2009
Location: Brisbane, Australia
Posts: 3
Default PDL size and manufacturer specific parameter ID's


This is a question regarding an RDM controller generating GET and SET messages for manufacturer specific parameter ID's, based on the information obtained from using the PARAMETER_DESCRIPTION command.

The response to a PARAMETER_DESCRIPTION command includes the "PDL Size" field, which corresponds to GET_RESPONSE and SET PDL sizes, but what about GET and SET_RESPONSE PDL sizes??

Get/Set DMX Curve command
GET takes in channel (PDL size = 1)
GET_RESPONSE replies with channel and curve (PDL size = 2)
SET takes in channel and curve (PDL size = 2)
SET_RESPONSE replies with no data (PDL size = 0)

So the PDL size field under PARAMETER_DESCRIPTION would be 2 to match GET_RESPONSE and SET, but there is no indication as to how much data to use with GET.

Has anyone come up with a solution/workaround for this?? Note that the controller I'm developing is hand-held with limited firmware, so it's not feasible storing the required information for manufacturer specific id's.

One possible workaround I've thought about is first attempting GET with a PDL size the same as GET_RESPONSE/SET (after allowing the user to set as many data fields as they like up to the GET_RESPONSE/SET PDL size), and if a NACK is received, keep reducing the PDL size of GET until an ACK is received.

Any thoughts on this would be greatly appreciated.

Creative Lighting
jamie is offline   Reply With Quote