uses length as the number of values to poll. With 32-bit data types, it requests twice as many
registers as the length.
An uncommon cause for the -02 result is a device with an incomplete implementation of
Modbus. Some devices do not fully implement parsing Modbus commands. Instead, they are
hard coded to respond to certain Modbus messages. The result is that the device will report an
error when you try selectively polling registers. Try requesting all of the registers together.
Result code -11: COM port error
Result code -11 occurs when the data logger is unable to open the COM port specified. For serial
connections, this error may indicate an invalid COM port number. For Modbus TCP, it indicates a
failed socket connection.
If you have a failed socket connection for Modbus TCP, check your
TCPOpen()
instruction. The
socket returned from
TCPOpen()
should be a number less than 99. Provided the data logger
has a working network connection, further troubleshooting can be done with a computer
running Modbus software. Connect the computer to the same network and attempt to open a
Modbus TCP connection to the problem slave device. Once you resolve the connection between
the computer and the slave device, the connection from the data logger should work.
15.3 Internet Communications
The internet protocols listed in
(p. 193), are supported by the
CR310 or when using a cell modem with the CR300 series. The most up-to-date information on
implementing these protocols is contained in CRBasic Editor help.
CRBasic instructions for internet communications include:
l
EmailRelay()
l
EmailSend()
l
EmailRcv()
l
FTPClient()
l
HTTPGet()
l
HTTPOut()
l
HTTPPost()
l
HTTPPut()
l
IPInfo()
l
PPPOpen()
l
PPPClose()
l
TCPOpen()
l
TCPClose()
See the CRBasic Editor help for detailed instruction information and program examples:
https://help.campbellsci.com/crbasic/cr300/.
15. Communications protocols
96
