TROUBLESHOOTING THE ADAPTER CARD WITH A LOOPBACK CONNECTION
PCI-AC48 User’s Guide
16
1.
To create the loopback connection, remove the communication cable from the adapter card.
Tie the TX pins on Port A to the RX pins on Port B (a four-wire configuration is required for a
loopback connection).
2.
Use a software program such as HyperTerminal to send data to the adapter card. Be sure to set
flow control for “None.”
Because of the loopback connection, any data sent to the adapter card will be transmitted out
the transmit (TX±) terminals, looped back into the receive (RX ±) terminals, and finally sent
back to the computer through the adapter card.
3.
Type characters on the computer’s keyboard and watch to see if they appear on the computer
screen.
If the data typed on the computer’s keyboard appears on the computer’s monitor, then the
adapter card is functioning correctly.
4.
Watch the TX and RX LEDs.
If the TX LED blinks, the adapter card received the data from the computer and transmitted it
out the transmit (TX±) terminals. If the RX LED blinks, the adapter card received the data.
If the TX LED does not blink, check the COM port number you are using in HyperTerminal to
make sure it matches the COM port number assigned to Port A.
Troubleshooting I/O Communications Using LED Indicators
If you are having difficulty communicating, you can watch the adapter card’s and Opto 22 brain’s
LEDs to help find the problem. It may be necessary to use a slow baud rate so the LED activity is
easier to see.
1.
When transmitting, did the TX LED on the adapter card blink? If it did, then the adapter card
transmitted a message; go to the next step.
If the LED did not blink, check the COM port number you are using to make sure it matches the
COM port number assigned to Port A.
2.
Did the Receive LED (RX, REC, RCV) on the Opto 22 brain or controller blink? If it did, then the
Opto 22 device received a message; go to the next step.
If the LED did not blink, then there is either a power problem at the device or a
communications wiring problem. Ensure that the voltage at the device is 5.0 VDC (±0.1 VDC).
Double-check the communications wiring.
Port A
Port B
1 2 3 4 5 6 7 8 9 10
1 2 3 4 5 6 7 8 9 10
TX
+
TX
–
RX
+
RX
–
