Campbell Scientific CR23X Micrologger - Manual (Page 73)

5-1
SECTION 5. TELECOMMUNICATIONS
Campbell Scientific has developed a software package which automates data retrieval and facilitates the
programming of Campbell Scientific dataloggers and the handling of data files. This package, PC208W,
has been designed to meet most needs in datalogger support and telecommunications. Therefore,
information in this section is not necessary for most datalogger applications.
Telecommunications is used to retrieve data from Final Storage directly to a computer/terminal and to
program the CR23X. Any user communication with the CR23X that makes use of a computer or
terminal is done through Telecommunications.
Telecommunications can take place over a variety of links including:
•
SC32A and ribbon cable/SC929 cable
•
Telephone
•
Cellular phone
•
Radio frequency
•
Short haul modem and twisted pair wire
•
Multi-drop interface and coax cable
This section does not cover the technical interface details for any of these links. Those details are
covered in Section 6 and in the individual manuals for the devices.
Data retrieval can take place in either BINARY or ASCII. The BINARY format is 5 times more compact
than ASCII. The shorter transmission times for binary result in lower long distance costs if the link is
telephone and lower power consumption with an RF link. On "noisy" links shorter blocks of data are
more likely to get through without interruption.
For more efficient data transfer, binary data retrieval makes use of a signature for error detection. The
signature algorithm assures a 99.998% probability that if either the data or its sequence changes, the
signature changes. Campbell Scientific’s PC208W Datalogger Support Software uses the binary format
for data transfer.
This section does not furnish sufficient detail to write telecommunications software. Appendix C contains
some details of binary data transfer and Campbell Scientific’s binary data format. The emphasis of this
section is on the commands that a person would use when manually (i.e., keyed in by hand)
interrogating or programming the CR23X via a computer/terminal. These commands and the responses
to them are sent in the American Standard Code for Information Interchange (ASCII).
The telecommunications commands allow the user to perform several operations including:
•
trouble shoot a problematic communications link
•
check the datalogger’s status
•
monitor data in Input Storage and review data in Final Storage
•
retrieve Final Storage data in either ASCII or BINARY
•
open communications with the Storage Module
•
remote keyboard programming
The Remote Keyboard State (Section 5.2) allows the user with a computer/terminal to use the same
commands as on the CR23X keypad.
5.1 TELECOMMUNICATIONS
COMMANDS
When a modem/terminal rings the CR23X, the
CR23X should answer almost immediately.
Several carriage returns (CR) must be sent to
the CR23X to allow it to set its baud rate to that
of the modem/terminal (300, 1200, 2400, 4800,
9600, 19.2K, 38.4K, or 76.8K). Once the baud
rate is set, the CR23X will send back the
prompt, "
∗∗∗∗
", signaling that it is ready to receive a
command.