Campbell CR800 Especificações descarregar pdf (Página 297)

Section 14. PakBus Networking

14-13

In some RF4xx networks with routers, neighbor filters are employed to

eliminate unreliable RF links. The idea is to prevent a needed router from

being bypassed in favor of a direct link. PakBusGraph Ping Node is used to

characterize a link and determine the need to force a route using a neighbor

filter (see 14.2.3). Sometimes a carefully designed blend of beaconing and

neighbor filters can be employed.

Whether you use beacons, neighbor filters, or both, the basic mechanism of

neighbor discovery is the hello-exchange. Any of the following events can

cause a hello packet to be directed to a specific PakBus device:

• LoggerNet tries to connect to a potential neighbor in its device map

• A PakBus device hears a beacon

• A neighbor filter is configured

The success of a hello-exchange depends on several things. The hello’d device

must have room in its neighbor list for another neighbor. CR2xxs accept only

one buddy (see glossary). For a successful hello-exchange, the hello’d device

cannot have a neighbor filter that excludes the helloing device. A helloing

device with address ≥ 4000 cannot be excluded by a neighbor filter.

If you create the LoggerNet map below (with correct baud rate) and provide a

communication link such as RF4xxs or an RS-232 cable, then open Connect

Screen and click on Connect, LoggerNet will send some low-level packets

including a hello packet directed to PakBus address 1. If a CR800 with

PakBus address 1 receives the hello and responds successfully, they become

neighbors. At this point high-level datalogger communications are possible

(program send, data collect, etc.) and the background sharing of low-level

network routing information begins.

For information on PakBus packet types obtain the PakBus Networking Guide

available in pdf format at http://www.campbellsci.com under Support/Manuals.

14.3.4 Neighbor Removal

Neighbor status between PakBus devices must be renewed periodically. It will

expire in the absence of successful communications in the form of either (1)

normal communications such as data collection, or (2) a verification

communication (hello-exchange). Communication verification will

automatically be attempted in the absence of normal communications when the

verification interval expires.

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Campbell CR800 Especificações Página 297