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6.3
Programming
The normal serial port instructions such as SerialOpen() and SerialIn() are
used with the SDM-SIO1A. Aside from changes to the COMPort and the
SerialOpenFormat parameter, a program written for a standard serial port will
usually work with the SDM-SIO1A. The main difference to be aware of, when
trying to write fast running programs, is the extra delay needed to transfer data
from the SDM-SIO1A to the datalogger (roughly equivalent to transferring
data over a serial link at 38 kilobaud).
The following section gives further information about the CRBasic
programming language and how the serial instructions are to be used with the
SDM-SIO1A.
This section assumes the user has knowledge of the CRBasic programming
language. A useful introduction to programming for serial sensors can be found
here:
https://s.campbellsci.com/documents/sp/technical-papers/serial.pdf
Please contact Campbell Scientific for further assistance or training. Campbell
Scientific's user forum is also a useful resource to check if others might have
already written code for a specific serial device.
Only the parameters that need special explanation or whose functionality has
changed when used with the SDM-SIO1A are listed below. Any other
parameters should be taken as not having changed. Please refer to the
datalogger manual and/or the CRBasic Editor help system for more guidance.
6.3.1 CRBasic Instructions
6.3.1.1 SerialOpen()
All internal buffers in the SDM-SIO1A will be flushed when this instruction is
called, resulting in the loss of any data that might have been in them at that
point in time.
•
•
•
COMPort
The COMPort numbers are defined in TABLE 6-1, SDM Address Settings
. COM port numbers in the range of 32 to 47 are reserved for use with
(p. 8)
the SDM-SIO1A.
BaudRate
BaudRate is used to set up the SDM-SIO1A baud rate as you would with
any RS-232 interface. The SDM-SIO1A does not support automatic baud
rate recognition. Instead, setting the rate to a negative number sets the
automatic flow control system (RTS/CTS). This system is discussed in
greater detail in Section 7.1.1, Using RTS/CTS and Automatic
Handshaking
.
(p. 22)
SerialOpenFormat
This parameter sets the data format. It also determines whether the
SDM-SIO1A works in normal RS-232, listen-only RS-232, full-duplex
RS-485, or half-duplex RS-485 mode as defined in the tables below.
SDM-SIO1A Serial Input/Output Module
15
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