Some communications types require more than one terminal, and some are only available on
specific terminals. This is shown in the datalogger specifications.
2.4.3.1 SDI-12 ports
SDI-12 is a 1200 baud protocol that supports many smart sensors. C1, C3, C5, and C7 can be
configured as SDI-12 ports. Maximum cable lengths depend on the number of sensors
connected, the type of cable used, and the environment of the application. Refer to the sensor
manual for guidance.
For more information, see SDI-12 communications (p. 94).
2.4.3.2 RS-232, RS-485, TTL, and LVTTL ports
RS-232, RS-485, TTL, and LVTTL communications are typically used for the following:
l Reading sensors with serial output
l Creating a multi-drop network
l Communications with other dataloggers or devices over long cables
Configure C terminals as serial ports using Device Configuration Utility or by using the
SerialOpen() CRBasic instruction. C terminals are configured in pairs for RS-232 or half-
duplex RS-485. For full-duplex RS-485, all terminals are required. See also Communications
Protocols (p. 81).
2.4.3.3 SDM port
SDM is a protocol proprietary to Campbell Scientific that supports several Campbell Scientific
digital sensor and communications input and output expansion peripherals and select smart
sensors. It uses a common bus and addresses each node. CRBasic SDM device and sensor
instructions configure terminals C1, C2, and C3 together to create an SDM port. Alternatively,
terminals C5, C6, and C7 can be configured together to be used as the SDM port by using the
SDMBeginPort() instruction.
See also Communications specifications (p. 173).
2.4.4 CS I/O port
One nine-pin port, labelled CS I/O, is available for communicating with a computer through
Campbell Scientific communications interfaces, modems, and peripherals. Campbell Scientific
recommends keeping CS I/O cables short (maximum of a few feet). See also Communications
specifications (p. 173).
2. Wiring panel and terminal functions 13
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