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Old November 6th, 2008   #1
Junior Member
Join Date: Sep 2006
Location: Colorado Springs
Posts: 6
Default Must a device support 32 charecters in DEVICE_LABEL?


Please verify or correct my interpretation of the PD field in DEVICE_LABEL.

I think if a device supports DEVICE_LABEL it must be able to accept and store no less than 32 characters.


A controller must send a GET DEVICE_LABEL after a SET to see what was retained.

On p. 62, the spec states that the data fields for both GET and SET DEVICE_LABEL commands are variable up to 32 characters but does not state that a device must accept 32 characters.

I have encountered an actual implementation where the device will only save 16 characters. (perhaps a hold over from a draft version of the spec?) If it receives a SET DEVICE_LABEL with more than 16 characters it truncates the text and replies with an ACK. This response marginally valid since the device did store some of the data and there is no way for it to tell the controller how large a text label it does support. I don't think a NACK NR_PACKET_SIZE_UNSUPPORTED response is valid here since the buffer for RDM messages is not the limitation, just the amount of memory allocated for a device label. No other NACK reason seems to fit unless the controller sends a field with more than 32 characters to which the NACK NR_FORMAT_ERROR would apply.

Thanks - Patrick
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