Campbell CR3000 Micrologger, Operator'S Manual

Page: 467 / 644

Section 8. Operation
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When using GetVariables() / SendVariables() to send values between
dataloggers, put the data in an array and use one command to get the
multiple values. Using one command to get 10 values from an array and
swath of 10 is much more efficient (requires only 1 transaction) than
using 10 commands to get 10 single values (requires 10 transactions).
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Set the CR3000 to be a PakBus router only as needed. When the
CR3000 is a router, and it connects to another router like LoggerNet, it
exchanges routing information with that router and, possibly (depending
on your settings), with other routers in the network.
•
Set PakBus beacons and verify intervals properly. For example, there is
no need to verify routes every five minutes if communications are
expected only every 6 hours.
8.9.3 Initiating Comms (Callback)
Comms sessions are usually initiated by a PC. Once comms are established, the
PC issues commands to send programs, set clocks, collect data, etc. Because data
retrieval is managed by the PC, several PCs can have access to a CR3000 without
disrupting the continuity of data. PakBus® allows multiple PCs to communicate
with the CR3000 simultaneously when proper comms networks are installed.
Typically, the PC initiates comms with the CR3000 with datalogger support
software
(p. 615).
However, some applications require the CR3000 to call back the
PC (initiate comms). This feature is called 'Callback'. Special LoggerNet
(p. 615)
features enable the PC to receive calls from the CR3000.
For example, if a fruit grower wants a frost alarm, the CR3000 can contact him by
calling a PC, sending an email, text message, or page, or calling him with
synthesized-voice over telephone. Callback has been used in applications
including Ethernet, land-line telephone, digital cellular, and direct connection.
Callback with telephone is well documented in CRBasic Editor Help (search term
"callback"). For more information on other available Callback features, manuals
for various comms hardware may discuss Callback options.
Caution When using the ComME com port with non-PakBus protocols,
incoming characters can be corrupted by concurrent use of the CS I/O for
SDC comms. PakBus comms use a low-level protocol (pause / finish /
ready sequence) to stop incoming data while SDC occurs.
Non-PakBus comms include TCP/IP protocols, ModBus, DNP3, and
generic, CRBasic-driven use of CS I/O.
Though usually unnoticed, a short burst of SDC comms occurs at power-
up and other times when the datalogger is reset, such as when compiling
a program or changing settings that require recompiling. This activity is the
datalogger querying to see if the CR1000KD Keyboard/Display is
available.
When DevConfig and PakBus Graph retrieve settings, the CR3000
queries to determine what SDC devices are connected. Results of the