Campbell RF401, Инструкция по эксплуатации, Страница: 125 / 130

M-1
Appendix M. PakBus Networking
Details
M.1 PakBus Aware, PakBus Node, and RF PakBus
Both the PakBus Aware and PakBus Node settings use the RF PakBus Protocol
allowing radios with these settings to coexist in the same network (i.e., some
radios can be PakBus Aware and some PakBus Nodes). The PakBus Aware
protocol does not require the assignment of a unique PakBus address, whereas
each radio with the PakBus Node protocol must have a unique address (the
default PakBus address is 1). The PakBus Node protocol also allows the radio
to be set up as a standalone RF Router (see Appendix M.7 , RF Router
(p. M-3)
).
If it is not enabled as a router, it will appear in PakBus Graph as a leaf node to
the attached datalogger (or server), as long as the datalogger is a router that
doesn’t exclude (via the Hello list) the address of the radio.
The RF PakBus Protocol works in conjunction with PakBus and compensates
for the interference and collision problems inherent in RF networks.
The RF PakBus Protocol:
1. Minimizes the number of small link state packets transmitted over RF.
2. Maximizes the RF packet size.
3. Establishes an ad hoc point-to-point link with RF packet acknowledgments
and retries.
M.2 Minimizing the Number of Small Link State
Packets
Empty PakBus link state packets are responded to locally, over the wired
interface of the radio, rather than sending them out over RF and having the
response come back over RF. This is beneficial because it reduces RF traffic.
Specifically, the link state packets that are handled locally (or “spoofed”) are:
•
RING packets; response is a READY packet
•
FINISHED packets; response is an OFF packet
• PAUSE packets; response is a FINISHED packet
• OFF packet; no response generated
M.3 Maximizing the RF Packet Size
The radio module’s RF packet size is changed from the default 64 bytes to its
maximum, 256 bytes, and the baud rate is increased to 38.4 kbps. Changing
the packet size and baud rate allows PakBus packets smaller than 256 bytes to
fit within one RF packet and larger PakBus packets to use fewer RF packets.