Section 8. Operation
• Control — CRBasic program language logic can allow remote access to
many control functions by means of changing the value of a variable.
— Set variables / flags / ports
• Clock Functions — Clock functions allow a web client to monitor and
set the host CR800 real time clock. Read the Time Syntax section for
more information.
— Set CR800 clock
• File Management — Web API commands allow a web client to manage
files on host CR800 memory drives. Camera image files are examples
of collections often needing frequent management.
— Send programs
— Send files
— Collect files
API commands are also used with Campbell Scientific’s RTMC web server
datalogger support software
(p. 86). Look for the API commands in CRBasic
Editor Help.
8.10.2 DNP3 — Details
Related Topics:
• DNP3 — Overview (p. 79)
• DNP3 — Details (p. 436)
See the technical paper DNP3 with Campbell Scientific Datalogger, which is
available at https://www.campbellsci.com/app-notes.
8.10.3 Modbus — Details
The CR800 supports Modbus master and Modbus slave communications for
inclusion in Modbus SCADA networks. Modbus is a widely used SCADA
communication protocol that facilitates exchange of information and data between
computers / HMI software, instruments (RTUs) and Modbus-compatible sensors.
The CR800 communicates with Modbus over RS-232, (with a RS-232 to RS-
485 such as an MD485 adapter), and TCP.
Modbus systems consist of a master (PC), RTU / PLC slaves, field instruments
(sensors), and the communication-network hardware. The communication port,
baud rate, data bits, stop bits, and parity are set in the Modbus driver of the master
and / or the slaves. The CR800 supports RTU and ASCII communication modes
on RS-232 and RS485 connections. It exclusively uses the TCP mode on IP
connections.
Field instruments can be queried by the CR800. Because Modbus has a set
command structure, programming the CR800 to get data from field instruments is
much simpler than from serial sensors. Because Modbus uses a common bus and
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