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SDM-SIO1A Serial Input/Output Module
The SDM-SIO1A is implemented in such a way that it looks like a built-in
serial port to the user when writing programs in CRBasic. The only difference
in operation between the SDM-SIO1A and a built-in port is that there will be a
small delay as the data needs to be transferred from the SDM-SIO1A to the
datalogger via the SDM port. That delay is usually only significant if large
amounts of data are being read or the datalogger program needs to run very
fast.
For sending and receiving data, the SerialOpen() instruction is used to specify
which serial port, the speed, and mode of operation. The speed is set by the
BaudRate parameter in the instruction and the mode (bits, parity, duplex, RS-
232 or RS-485) is set by the SerialOpenFormat parameter. Refer to the
CRBasic Editor help system for more details of the options. With the correct
parameters in the SerialOpen() instruction, the program can be written in
almost exactly the same way as using any other serial port with SerialIn(),
SerialOut(), and similar instructions. Section 6.3, Programming
, of this
(p. 15)
manual gives details of some of the minor changes needed and some simple
program examples.
The SDM-SIO1A can also be used as an interface to Modbus and DNP3
sensors or networks. The interface is configured by including an extra
SerialOpen() instruction at the start of the program. Normal calls to the
relevant Modbus or DNP3 instructions can then be used specifying the
COM port number relevant to the SDM-SIO1A.
6.1
Mounting
The SDM-SIO1A is normally mounted on the backplate of a Campbell
Scientific enclosure using the screws and plastic inserts provided. The
SDM-SIO1A is designed to be installed in a dry, non-condensing environment.
Before mounting, select and set the SDM address as this requires access to the
side of the case. The SDM address is set with a screwdriver. TABLE
6-1
lists
the possible SDM addresses and their relationships to the COMPort parameter
in the SerialOpen() instruction.
There can be up to 15 SDM-SIO1As on a single SDM bus. Each SDM-SIO1A
will need to be set to a unique address before they are powered. If any other
equipment is present on the bus, whether an SDM-SIO1A or other SDM
device, the user will have to ensure their addresses are unique.
7
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