Campbell Scientific CR800 and CR850 Measurement and Control Systems - Manual (Page 203)

Section 7. Installation
203
7.8.8.2 I/O Ports
The CR800 supports two-way serial communication with other instruments
through ports listed in table CR800 Serial Ports
(p. 203).
A serial device will often
be supplied with a nine-pin D-type connector serial port. Check the manufacture's
pinout for specific information. In most cases, the standard nine-pin RS-232
scheme is used. If that is the case then,
• Connect sensor RX (receive, pin 2) to datalogger Tx (transmit, channel C1,
C3).
• Connect sensor TX (transmit, pin 3) to datalogger Rx (receive, channel C2,
C4).
• Connect sensor ground (pin 5) to datalogger ground (G terminal)
Note Rx and Tx lines on nine-pin connectors are sometimes switched by the
manufacturer.
Table 31. CR800 Serial Ports
Serial Port Voltage Level Logic
RS-232 (9-pin) RS-232 Full-duplex asynchronous RS-232
CS I/O (9-pin) TTL Full-duplex asynchronous RS-232
COM1 (C1 - C2) TTL Full-duplex asynchronous RS-232/TTL
COM2 (C3 - C4) TTL Full-duplex asynchronous RS-232/TTL
C1 5 VDC SDI-12
C3 5 VDC SDI-12
C1, C2, C3 5 VDC
SDM (used with Campbell Scientific
peripherals only)
7.8.8.3 Protocols
PakBus is the protocol native to the CR800 and transparently handles routine
point-to-point and network communications among PCs and Campbell Scientific
dataloggers. Modbus and DNP3 are industry-standard networking SCADA
protocols that optionally operate in the CR800 with minimal configuration by the
user. PakBus®, Modbus, and DNP3 operate on the RS-232, CS I/O, and four
COM ports. SDI-12 is a protocol used by some smart sensors that requires
minimal configuration on the CR800.
Read More! See SDI-12 Recording
(p. 308),
SDI-12 Sensor Support
(p. 173),
PakBus
Overview
(p. 334),
DNP3
(p. 347),
and Modbus
(p. 350).
Many instruments require non-standard protocols to communicate with the
CR800.
Note If an instrument or sensor optionally supports SDI-12, Modbus, or DNP3,
consider using these protocols before programming a custom protocol. These
higher-level protocols are standardized among many manufacturers and are easy
to use, relative to a custom protocol. SDI-12, Modbus, and DNP3 also support