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+--- Thread: Unable to connect to COM Port greater than COM20 (/showthread.php?tid=374)
Unable to connect to COM Port greater than COM20 - n1eu - 11-24-2017
Whenever I remove and re-pair my bluetooth GPS receiver, Windows 10 assigns a new COM port pair and increments the port number. I am now at COM24 for the output port and BktTimeSync seems unable to list available COM ports over COM20. Can you possibly add support for higher COM port numbers?
Thanks & 73,
Barry N1EU
RE: Unable to connect to COM Port greater than COM20 - n1eu - 11-26-2017
I found a work-around solution to this after much searching. Windows marks COM ports as used once they are allocated. Bluetooth Devices keeps incrementing the COM ports when you re-pair the GPS because it thinks the old COM ports are in use. You need to go into regedit and change the value of HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\COM Name Arbiter\ComDB - you can find details at http://www.ftdichip.com/Support/Documents/AppNotes/AN_132_Re-Assigning_COM_Port_Numbers_Using_Registry.pdf - every COM port has a bit in the ComDB value that is set to 0 if it's available or 1 if it is not. So you need to change the 1's to 0's and then you will once again be able to assign the lower COM ports.
RE: Unable to connect to COM Port greater than COM20 - iz2bkt - 11-27-2017
Hi Barry,
you can also change the port number from the device window. Look here : https://plugable.com/2011/07/04/how-to-change-the-com-port-for-a-usb-serial-adapter-on-windows-7/
RE: Unable to connect to COM Port greater than COM20 - n1eu - 12-04-2017
No, that method will not work Mauro if the COM port number has been used before and the bit was never reset in the ComDB registry key. I tried that method first and it told me the COM port was already in use so I had to go into the registry and clear it.