Section 4 RS232 Communication
The RS232 port provides the customer with bi-directional data transfer via a
three-conductor cable consisting of signal ground, receive input, and transmit
output. It is recommended that less than fifty feet of shielded cable be used
between the computer and this instrument. This will assure performance of
the BB-4A to EN61326, under the E.M.C. Note that multiple instruments cannot
be tied to the same port in this configuration. The RS232 port is optically isolated
to eliminate ground loop problems.
Below is a pinout diagram for the serial port of the BB-4A as well as the pinout
for a 9-pin PC serial port. Use a straight DB9 (female) to DB9 (male) connector
cable to connect your computer to the BB-4A. The cable should be attached when
only when the computer and BB-4A are off.
Only parameters in the parameter list should be modified or queried via the
serial port. Other parameters should be viewed or queried from the controller,
directly. It is highly recommended that baud rate for the controller be modified
on the controller, directly. Note that both the BB-4A and the computer must be
communicating with the same serial communications parameters to establish a
working communication link.
The serial communications feature can be tested using terminal emulation
package. Note that this controller does not time out waiting for the next
character to be transmitted. Be sure not to use the XON/XOFF or hardware
handshaking. Lastly, it should be noted that following a complete transmission
to the BB-4A, a response it sent back. If the message was valid, the changed or
queried parameter is echoed back (following the same format). If the message
was not according to acceptable format or was attempting to force a parameter
out of range, an “ERROR” message is echoed.
Figure 7. Connecting the BB-4A to a Computer’s Serial Port
BB-4A Blackbody Calibrator
4
4-1
1
6
7
8
9
6
7
8
9
2
3
4
5
1
2
3
4
5
TX
RX
GND
RX
TX
GND
BB4A
BLACKBODY
CALIBRATOR
REAR PANEL
YOUR
COMPUTER
SERIAL
PORT
(RS232)