I cannot access the serial port, COM1:. I used to be able to but now any app, such as Hyperterminal, that tries to open COM1: puts up a small info window that says "Unable to open COM1. Please check your port settings."

Any idea what might be causing this?

According to Device Manager the port is working correctly.

I'm wondering if another auto started app that I don't know about has opened the port. Is there any way to find out what apps have opened the serial ports on the PC?

I'm running Win XP home with all service packs and updates.

Any help really appreciated.


It'd be pretty tough to chase down who's using it. You could try uninstalling it and restarting the machine to let it reinstall.

Thanks for the idea. I found that Device Manager showed a Standard 19200 baud modem was using COM1:. I first disabled it then uninstalled it (including re-boots) but this made no difference.

Finally uninstalled the COM1: device, re-booted (which found the 'new' device and installed it) and all is now working.

The help is appreciated.

Weird. Maybe the modem got confused, I would think it would want COM3 rather than COM1.

The uninstall-reboot-install new device cycle seldom fails :)

Don't forget to mark your thread "solved" if you're all squared away.

Wierd indeed, on the other hand we are talking about win xp. Got to admit though it's better than its predecessors.
Thanks again.

Try this : Ensure this port is not already open. Disconnect serial cable from embedded system(now connection only with PC )and try again to connect in hyperterminal if it is okay then connect cable to embedded board.