USB-RS232 Converter Does not appear in list of comm ports

I am trying to use the converter to connect an RS-232 connected customer pole display to our PC.

When I query the list of active comm ports, the device does not appear. I’m not sure where to begin troubleshooting this.


Hi mmorgan.mandy,

Thanks for contacting Plugable Support. We’ll be happy to help!!! To start troubleshooting your issue, I’ll need a little more information. Can you tell me what Operating System you’re using? Also what make and model of computer are you connecting to? Have you run the install disc that comes with the cable? It includes both Mac and Windows versions of installer programs.

Let me know about these details and we’ll figure out where to go from there.


Hi Jerome,

Sorry, I should have included that info.
Windows 7, HP TouchSmart 310, Yes I have run the installer disc.

The application that’s trying to use the port is our POS app, a Java app that uses RXTX to communicate with the port. I developed the Java app, so I can certainly do whatever is needed from that end.

As I said, the comm port for the display doesn’t appear in the list of available ports.

Hi Again,

Thanks for the additional information! So, you’ve probably already looked into this but, just for a sanity check, does the USB to Serial adapter show up in device manager? You should have a listing under Ports (COM & LPT). It should be called Prolific, and have a COM number assigned after it. To communicate through the USB cable, just use the assigned COM number in your software. For testing purposes, you may need to find another serial device and use a standard terminal program like HyperTerm or Putty to rule any device issues, but if the COM number is listed, it’s probably installed correctly.

Hope this help,
Let me know how it goes!

Hi Jerome,

The device does appear in the device manager in Windows 7, but when I scan the available serial ports with the java app it does not appear.

I am having the same issue in OSX. I have run the installer, plugged in the adapter, and it does not appear when I scan the system for available ports. I have tried issuing the command:

ls /dev/tty*

Nothing obviously looks like the Plugable adapter. What should I be looking for?


Hi Matt,

In Mac OS X you can see the usb serial device under /dev/tty.usbserial. As far as on Windows you can see it under device manager, ports (COM and LPT) where it will be assigned a COM number, as long as it’s there and has a COM number assigned then it should be a functioning Windows device. We’re limited in our Java expertise but I did find what looks to be a good place to start here.

To be sure that the device is working, you’ll need to use a known working application first, and then troubleshoot the new Java code. However, if the device is showing up in Device Manager and has a COM number assigned, it is most likely working.

Hope this helps,