Industrial RS232 to RS422/485 Serial Port Converter with 15KV ESD Protection

When you troubleshoot issues with a serial device, there are some quick tests that you can complete to rule out potential problems. You can test to make sure that the following components are working correctly and are not the source of the issue:

• Serial cables

• Serial ports

• Serial devices

To test your setup components, try the following:

• Use the serial cable, serial port, and serial device in another setup to see if the problem is with the components or the setup.

• Use a different serial cable, serial port, and serial device in your setup to see if the problem persists. Ideally, you should test a component that you know works in another setup.

When you test your cables, it is recommended that you do the following:

• Test each cable individually.

• Use short cables when you are testing.

When you test the serial ports and serial device, it is recommended that you do the following:

• Press the Windows key + R, type devmgmt.msc, and press Enter to open Device Manager. Check to see if your device is listed under Ports (COM & LPT).

• Make sure that the COM port number is the correct number for the serial device and that the software being used to connect the computer to the serial device uses the correct COM port number. 

• If the device is listed with an error, follow the instructions on the website to reinstall the drivers.

Note: Some serial devices work only if the COM port number is between a certain range. For example, COM1 to COM4.

• Perform a serial loopback test.  See this FAQ on how to perform a RS-232 serial loopback test: http://www.startech.com/faq/serial_loopback_test_rs232_windows

To check whether or not an RS-232 serial port is working, perform an RS-232 loopback test by doing the following:

1. If your serial port is not female, convert it by taking a female/female cable or gender changer and plugging it into the serial port.
2. Take a metal paperclip or wire and cross pins 2 and 3. If you look closely at the female end, the pins should be numbered.
3. Open a telnet session on the COM port number of the device that you are testing. To find out the COM port number, refer to the following FAQ: https://www.startech.com/faq/com-port-listing-windows.

Note: To open a telnet session on the COM port, you need a telnet client like PuTTY or Hyper Terminal. Windows XP comes with Hyper Terminal.

4. When the session is open, anything you type into it you should see. The loopback test fails when you cannot see what you are typing.

If the loopback test fails, make sure that the serial cable or gender changer that you are using works and that the adapter is in the correct port. 

You can check multiple ports at the same time by opening multiple sessions, putting the loopback adapter on one port, and trying to type into each session.  When you can see what you are typing, you know that the COM port is working and you can see which port number the physical serial port is. Close the window for the port that you just tested to speed up the testing of the remaining serial ports.

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To check whether or not a RS-422 serial port is working, perform a RS-422 loopback test.

1. Convert your serial port to be female if it is not already.  You can do this by taking a female/female cable or gender changer and plugging it into the serial port. 
2. Take a metal paperclip or wire and cross pins T- with R- and T+ with R+.  The device or the manual should indicate what pins are T+, T-, R+ and R-.
3. Open a telnet session on the COM port number in question.  To find out the COM port number of the device you want to test, please see “How do I check to ensure the COM port is listed properly in Windows XP, Vista, 7 or 8?”
4. To open a telnet session on the COM port, you need a telnet client like PuTTY or Hyper Terminal. 
5. Note: Windows XP comes with Hyper Terminal.

When the session is open, anything you type into it you should see.  The loopback test fails when you cannot see what you are typing in this window.