Campbell CR800 Series, Руководство оператора

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Section 7. Installation
284
7.7.17.5 Serial I/O CRBasic Programming
To transmit or receive RS-232 or TTL signals, a serial port (see table
CR800
Serial Ports
(p. 280))
must be opened and configured through CRBasic with the
SerialOpen() instruction. The SerialClose() instruction can be used to close the
serial port. Below is practical advice regarding the use of SerialOpen() and
SerialClose() . Program CRBasic example
Receiving an RS-232 String
(p. 290)
shows the use of SerialOpen() . Consult CRBasic Editor Help for more
information.
SerialOpen (COMPort,BaudRate,Format,TXDelay,BufferSize)
•
COMPort — Refer to CRBasic Editor Help for a complete list of COM
ports available for use by
SerialOpen()
.
• BaudRate — Baud rate mismatch is frequently a problem when
developing a new application. Check for matching baud rates. Some
developers prefer to use a fixed baud rate during initial development.
When set to
-nnnn
(where nnnn is the baud rate) or
0
, auto baud-rate
detect is enabled. Autobaud is useful when using the CS I/O and RS-
232 ports since it allows ports to be simultaneously used for sensor and
PC comms.
•
Format — Determines data type and if PakBus
®
communications can
occur on the COM port. If the port is expected to read sensor data and
support normal PakBus
®
telemetry operations, use an auto-baud rate
argument ( 0 or -nnnn ) and ensure this option supports PakBus
®
in the
specific application.
•
BufferSize — The buffer holds received data until it is removed.
SerialIn() , SerialInRecord() , and SerialInBlock() instructions are used
to read data from the buffer to variables. Once data are in variables,
string manipulation instructions are used to format and parse the data.
SerialClose() must be executed before SerialOpen() can be used again to
reconfigure the same serial port, or before the port can be used to communicate
with a PC.
7.7.17.5.1 Serial I/O Programming Basics
SerialOpen()
1
•
Closes PPP (if active)
•
Returns TRUE or FALSE when set equal to a Boolean variable
• Be aware of buffer size (ring memory)