Campbell Scientific CR200/CR200X-series Dataloggers - Manual (Page 148)

Section 14. PakBus Overview
14.4.6 Maintaining Links
Links are maintained by means of the CVI (communications verification
interval). The CVI can be specified in each node with DevConfig. The following
rules 1 apply:
• If Verify Interval = 0, then CVI = 2.5 x beacon interval*
• If Verify Interval = 60, then CVI = 60 seconds*
• If Beacon Interval = 0 and Verify Interval = 0, then CVI = 300 seconds*
• If a router or master does not hear from a neighbor for one CVI, it begins
again to send a Hello message to that node at the random interval.
Users should base verification intervals on the timing of normal
communications such as scheduled LoggerNet collections or datalogger to
dataloggers communications. The idea is to not allow the verification interval to
expire before normal communications. If the verification interval expires the
devices will initiate hello exchanges in an attempt to regain neighbor status,
increasing traffic in the network.
Note: During the hello-message, a CVI must be negotiated between two
neighbors. The negotiated CVI is the lesser of the first nodes CVI and 6/5ths of
the neighbors CVI.
14.5 Troubleshooting
Various tools and methods have been developed to assist in troubleshooting
PakBus® networks.
14.5.1 Link Integrity
With beaconing or neighbor filter discovery, links are established and verified
using relatively small data packets (Hello messages). When links are used for
regular telecommunications, however, longer messages are used. Consequently,
a link may be reliable enough for discovery but unreliable with larger packets.
This condition is most common in radio networks, particularly when max packet
size is >200.
PakBus® communications over marginal links can often be improved by
reducing the size of the PakBus® packets. Best results are obtained when the
maximum packet sizes in both nodes are reduced.
1 During the hello-message, a CVI must be negotiated between two neighbors.
The negotiated CVI is the lesser of the first nodes CVI and 6/5ths of the
neighbors CVI.
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