Campbell Scientific HC2S3 Temperature and Relative Humidity Probe - Manual (Page 35)

Appendix C. HC2S3 Digital
Communications
C.1 HC2S3 Digital Interface Specifications
The HC2S3 has a UART (Universal Asynchronous Receiver Transmitter) that
provides two-way digital communications with the probe. Interface cables can
be ordered through Rotronics for connecting the probe to an RS-485 port
(Rotronic pn E2-05XX-MOD), a computer's RS-232 port (Rotronic
pn AC3002), or USB port (Rotronic pn AC3001).
Connections to a CSI datalogger through an MD485 RS485 Interface or
SDM-SIO1 Serial I/O Module with the Rotronic E2-05XX-MOD RS-485 cable
are described in Section C.3 and C.4 respectively.
HC2S3 Digital Interface Specifications:
Interface Type: UART (Universal Asynchronous Receiver Transmitter)
Organization: Dialog, duplex
Default Configuration:
Baud rate: 19200
Parity: none
Data bits: 8
Stop fits: 1
Flow Control: none
Logical Levels:
Logical 0: <= 0.3V*VDD
Logical 1: <= 0.8V*VDD
C.2 HC2S3 Communications Protocol
Complete information on the HC2S3 Commands and Communication Protocol
can be found in the Rotronic E-M-AC3000-CP_XX
manual, available from
Rotronic's website www.rotronic-usa.com .
The “RDD” command to “Read Values” is used in the example datalogger
programs to get temperature and relative humidity values from the probe, and
is described below.
RDD command: read values
Returns the measured and calculated values as well as the information
necessary to interpret the data (calculated parameter type, engineering units,
status, serial number and name of the device, etc.)
C-1