Re: [libpcap] New DLT value Request - Wattstopper DLM (#401)

[Steve Karg <skarg () users sourceforge net>]

Hello Guy,

> > The Family/Address/IR field contains 3-bits of family code, 2-bits of
> > address mode, 2-bits of IR (infrared) routing, and 1-bit unused.
> > The 8 Legrand NITOO families are 000=CAD Filaire, 001=TopDog, 010=CAD RF,
> > 011=CAD PLC, 100=CAD IR, 101=DLM, 111=escape, and 111=DLM Bootloader).
> > This document only describes the DLM family.
>
> Are the fields following the Family/Address/IR field dependent on the family code?  Or can the rest of the packet, 
> with the possible exception of the opcode and payload, be parsed the same way regardless of the family code?

Yes, the fields following the Family code are dependent on the Family code.

> Are the family codes dependent on the hardware being used?

Yes, the Family codes are dependent on the hardware.  The WattStopper
DLM hardware uses a USB interface:
http://www.wattstopper.com/products/digital-lighting-management/configuration-tools/dlm-computer-interface-tools-and-software.aspx
and also tunnels the DLM packets in BACnet messages.

Another Family is CAD PLC, part of Open-NITOO, but I don't know the
hardware interface:
http://www.myopen-legrandgroup.com/cfs-filesystemfile.ashx/__key/telligent-evolution-components-attachments/00-212-01-00-00-03-46-60/U3838B_5F00_Specifications.pdf

> > The Opcode field contains the message command, which determines the Payload
> > and Payload Length fields.
>
> Presumably the Payload Length field is the number of octets in the Payload field.

Yes, the Payload Length field is the number of octets in the Payload field.

> Is there some other specification to which we can point for the values of the Opcode field, and the corresponding 
> payload, or can this be used for several different families of opcodes (with the dissector presumably having to be 
> told which one to use)?  (The spec doesn't have to itself describe the opcode or payload values, although, if there's 
> a spec or specs for them, references to them might be useful.)

I don't have a public specification for the Opcodes at the moment.
Some are detailed in this Wireshark Lua dissector:
http://kargs.net/captures/irb.lua

> > The LRC Checksum excludes the Preamble octets.
>
> Does it cover the Dongle Code or Packet Delay field?

The LRC does not cover the Dongle Code or Packet Delay or Preamble.

Best Regards,

Steve
-- 
http://steve.kargs.net/
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