3 years, 5 months ago.

WIndows 10 Teraterm Serial Greyed Out


I know this has been asked before, but the solutions didn't work for me.

I bought a windows 10 laptop recently, downloaded teraterm for a cisco 2950 switch, but the serial is greyed out.

Under device manager, I see various errors for Prolific USB-to-serial comm port (com3). Most of the are "device cannot start, not enough quota (virtual memory)", but my laptop has plenty of specs and settings are to max for this device.

I've tried uninstal/reinstall, installing Ports (COM&LPT) as a legacy device, changed COM3 to different port numbers, and downloaded the drivers at https://developer.mbed.org/handbook/Windows-serial-configuration (got the "No mbed Microcontrollers were found" error), but no luck.

DIdn't have these issues with windows 8

Any advice on this would be appreciated.

Hi Oshikuru,

What target platform are you using?

-Andrea, team mbed

posted by Andrea Corrado 08 Sep 2016

3 Answers

3 years, 3 months ago.

I have had many issues with USB to serial cables and what I found on the web and by trying them is that the Prolific and FTDI drivers don't work with many/most of the low cost older USB to serial cables in Windows 10. The internet lore on this was that they have counterfeit chips and the new drivers made and paid for by Prolific and FTDI for new versions of Windows check for them and don't work unless it is one of theirs. So only get a cable that is known to work with Windows 10!

I had to throw out all of my low cost older USB/serial cables when upgrading Windows. Any attempt I made at finding a driver that works with old ones was in vain.

One new cable I found is here https://www.adafruit.com/products/18

Stay away from any that don't say "works with Windows 10!"

Accepted Answer

Thank you. Getting a new cable compatible with Windows 10 fixed the issue!

posted by Oshikuru Lee 18 Nov 2016
3 years, 5 months ago.

Have you checked with another USB to Serial cable , for example FTDI FT232R chip based ? It may be the specific cable driver . Sometimes these serial chips are not even original ones and have driver problems

3 years, 3 months ago.

I'm having this same problem, and I cannot figure out how to fix this. I've downloaded many drivers and nothing works. Has anyone found a solution to this problem.