Campbell Scientific CSAT3 3-D Sonic Anemometer - Manual (Page 59)

Appendix B. Serial Communications
with the CSAT3
B.1 CSAT3 RS-232 Commands
The CSAT3 powers up its RS-232 drivers when it detects that the RTS (request
to send) line has been asserted by the PC. All RS-232 communications begin
with the PC asserting the RTS line, the CSAT3 responds by asserting the CTS
(clear to send) line. The PC must keep the RTS line asserted as long as it is
communicating with the CSAT3.
RS-422 communications and short-haul modems do not include an RTS signal.
The CSAT3s RS-232 drivers can be asserted by a software setting in the
CSAT3. This setting will always power the RS-232 drivers, independent of the
RTS line.
The unprompted output mode (TABLE B-1) complicates anemometer data
processing software, because the original output format contains no fixed
pattern to delimit the CSAT3’s 10 byte output record. To configure the
CSAT3 to output 12-byte records, with the last two bytes being a fixed pattern
of AA55 hex, send an “rs n”, where n = 0 (default) means no synchronization
code and n = 1 means send the synchronization code, to the CSAT3. As is
customary in the DOS environment, 55 hex is transmitted first followed by AA
hex. This configuration will be lost if the CSAT3 power is cycled. To save
this configuration into non-volatile memory, issue the “sr2718” command (See
Section 12).
There are nine commands that may be sent to the CSAT3 over the RS-232
interface. These commands are described below. Before continuing on, read
the section that describes the CSAT3 Trigger (Section 8).
B-1