Instruction manual

B-1
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. Contact Campbell Scientific for details.
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 contact Campbell Scientific.
The CSAT3 supports 9600 and 19200 baud RS-232 communications rate. The baud rate is changed by
sending a “br n”, where n = 0 (default) is 9600 baud and n = 1 is 19200 baud. This configuration will be
lost if the CSAT3 power is cycled. To save this configuration into nonvolatile memory contact Campbell
Scientific.
There are nine commands that may been 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).
TABLE B-1. RS-232 Command Codes
Command Trigger before
Command
Description Trigger after
Command
& PC or CSAT3
timer
Unprompted data output mode. Send data and
make measurements at the rate specified by the
An command.
CSAT3 timer
P
1
CSAT3 timer
or PC
Send the RS-232 status (Table B-9) and trigger
the next measurement now.
PC
2
U
1
CSAT3 timer
or PC
Send the wind data and trigger the next
measurement now.
PC
2
S PC or
CSAT3 timer
Send the RS-232 status (Table B-9). The next
measurement will be made in sync with the
CSAT3 timer.
CSAT3 timer
W PC or
CSAT3 timer
Send the wind data. The next measurement will
be made in sync the CSAT3 timer.
CSAT3 timer
A(1..e)
1,3,4
PC or
CSAT3 timer
Begin acquiring the signals in sync with this
command.
No change
O SDM, PC, or
CSAT3 timer
Turn the analog outputs off in sync with the next
trigger.
No change
L SDM, PC, or
CSAT3 timer
Turn the analog outputs on with ±32 m s
-1
full-
scale range in sync with the next trigger
No change
H SDM, PC, or
CSAT3 timer
Turn the analog outputs on with ±64 m s
-1
full-
scale range in sync with the next trigger
No change