Chapter 5 – Troubleshooting
61
RS-232/485 Communication Problems
If you cannot establish RS-232 or RS-485 communications, the next sections give
instructions for procedures to help isolate problems.
Testing the COM Ports
Install and launch Motion Planner. See
Chapter 2 Installation
for information
about using this software tool.
RS-232 communications require that you use a null modem cable. See
Chapter 2
Installation
for connection instructions. Pinout diagrams for the Gem6K’s RS-232/
485 and RS-232 connectors are in
Chapter 4 Special Features
.
Testing the COM Ports with Motion Planner
1.
Install and launch Motion Planner.
2.
When the product selection dialog appears, select a Gem6K drive and select the
PC COM port to which the Gem6K is connected.
3.
If you see the error message “unable to connect to com
n”, then the wrong PC COM
port is selected, or the PC COM port is busy.
• Check the PC COM port setting again. Your PC may have multiple COM
ports. Try connecting to a different port.
• Check to see if another application is busy using the COM port. Close all
other applications.
If these steps do not solve your problem, see
Testing the Cable
, below.
Testing the Cable
Use the following two procedures to test your null modem cable, and to verify that
it is working properly.
“Loop Back” Test
1.
Connect one end of your RS-232 cable to your PC. Disconnect the other end of the
cable from the drive.
2.
Connect pin 2 to pin 3 on the drive end of the RS-232 cable.
3.
Launch Motion Planner and click the “Terminal” tab on the bottom of the screen to
enter terminal mode.
4.
Type several characters on the keyboard. These characters should appear on the
terminal screen as you type them.
If you are continuing to have trouble with communications, proceed to
Verifying a
Null Modem Cable
.
Verifying a Null Modem Cable
1.
Connect one end of your RS-232 cable to your PC. Disconnect the other end of the
cable from the drive.
2.
With no data being transmitted, measure the voltage on the RS-232 cable’s transmit
pin (should be pin 2). The voltage on the transmit pin should be in the range
-3VDC to -12VDC.
3.
Measure the voltage on the RS-232 cable’s receive pin (should be pin 3). The
voltage on the receive pin should be zero volts.
4.
Verify that the cable’s transmit pin connects to Pin 2 on the Gemini’s RS-232/485
connector.
This completes the test.
