Campbell Scientific CR200/CR200X-series Dataloggers - Manual (Page 121)

Section 11. Programming Resource
Library
11.1 Remote Sensor Interface
The CR200(X) is frequently used as a remote sensor interface for a “Host”
datalogger. Typically, the host datalogger and the sensor(s) (CR200(X)) will
have programs that will enable the sensors to operate with the minimum
quiescent current drain (110 µa). These programs synchronize the CR200(X)
sensors so that they are reporting back the data in designated time slots.
For applications demanding more frequent communication, the get/set variable
instructions in the host datalogger can be used with CR200(X) sensors that are
configured for higher current drain (250 µa for 8 second response; 20 ma for 1
second response).
In the lowest power, synchronized mode, the CR200(X) always initiates
communication. Except when it wakes up to send data, its radio is off, drawing
no power. The host datalogger’s radio will be in a fully on position during the
period of expected sensor communication, ready to receive and respond
instantly.
CRBASIC EXAMPLE 16. Example Wireless Sensor Program For CR200(X)
Const MT = 20 'Measurement Time (secs) SDI-12 in this Case takes 20 seconds
Const Port = 1 '1 = Radio, 2 = RS-232 To send out data
Const RouterAddr = 1 'the PakBus address of a router, in this Case the same as Host
Const HostAddr = 1 'the PakBus address of the Host datalogger
Const NumVals = 8 '8 Measurements
Const Security = 0 'use non zero If Host datalogger has Security set
Const NumControl = 4
Public Measurements(NumVals) 'sensor values To send
Public Control(NumControl) 'Control values returned from Host
BeginProg
Scan(1, sec)
If TimeUntilTransmit(Port)=MT Then 'If it Is time To measure start Measurement
'applicable Measurements that take MT seconds inserted here
EndIf
NextScan
EndProg
TimeUntilTransmit(port) is a function that returns the number of seconds before
it is time to communicate. It will use information retrieved from the datalogger
to determine the time remaining before its communication time slot.
SendGetData will output an array of measurements to the Host datalogger and
retrieve a time slot, a clock setting, and optionally an array of data from the Host
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