Modbus Communications; Dnp3 Communications; Pakbus Communications - Campbell CR300 Series Operator's Manual

CR300-Series Datalogger

6.5.4 Modbus Communications

6.5.5 DNP3 Communications

6.5.6 PakBus Communications

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The CR300 can be programmed to act as an SDI-12 data recorder or as an SDI-
12 sensor. The SDI12Recorder() instruction automates sending commands
and recording responses. With this instruction, the commands to poll sensors
and retrieve data are done automatically with proper elapsed time between the
two. The CR300 automatically issues retries. See CRBasic Editor Help for
more information on this instruction.
CRBasic SDI-12 instructions include:
• SDI12Recorder()
• SDI12SensorSetup()
SDI12SensorResponse()
•
The CR300 supports Modbus RTU and Modbus ASCII protocols and can be
programmed as a Modbus master or Modbus slave. These protocols are often
used in Modbus SCADA networks. The CR300 communicates with Modbus
over RS-232. Ports RS-232 and Com1 can be configured for Modbus RS-232
communication.
Modbus has a set command structure. It uses a common bus and addresses each
node, so field instruments are effectively multiplexed to a CR300 without
additional hardware.
CRBasic Modbus instructions include:
ModbusMaster()
•
ModbusSlave()
•
MoveBytes()
•
See CRBasic Editor Help for the most recent information on each of these
instructions and for program examples.
DNP3 (Distributed Network Protocol) is designed to optimize transmission of
data and control commands from a master computer to one or more remote
devices or outstations. Ports RS-232 and Com1 can be configured for DNP3
communication. See application note
Dataloggers, available at www.campbellsci.com, for detailed information and
program examples.
CRBasic DNP3 instructions include:
DNP()
•
DNPUpdate()
•
DNPVariable()
•
PakBus is a protocol similar in concept to IP (Internet Protocol). By using
signatured data packets, PakBus increases the number of communication and
networking options available to the CR300. Communication can occur via
TCP/IP, on the USB port, the RS-232 port, and the C terminals.
DNP3 with Campbell Scientific