Recently, I bought a Prolific USB-to-Serial adapter for flashing my Android smartphone that I had accidentally bricked. I found out the RXD, TXD and GND points on the mobile phone, connected them to the Prolific adapter, but the software refused to flash the mobile phone. The reason, that I figured out after many hours of hair pulling, was that the flashing software works only with COM 1, COM 2 and COM 3 while the Prolific USB-to-Serial adapter was selected automatically to use COM 11 in Windows. After changing the adapter port from COM 11 to COM 2, I was finally able to flash the mobile phone.
Some of the software are designed intentionally to work with a selected number of COM ports. In order to work with this type of software, you may have to change the COM port number for a connected device. Here is how you can change the COM port for any connected device in Windows:
- Connect the device for which you want to change the port to your PC. Let Windows detect the device. If the device is not PnP ready, then you may have to reboot the PC so that it is recognized.
- Press Win+R hotkey to open the Run dialog. In the Run dialog type devmgmt.msc and press Enter to open the Device Manager.
- In the Device Manager, you will be able to find the connected communication device under the Ports (COM & LPT). Select and right-click on the target device and choose Properties from the context-menu.
- In the Properties window, switch to the Port Settings tab and click on the Advanced button.
- In the Advanced Settings window that opens up, you can choose an available port number from the lower-left corner of the window. In the following screen shot, I have changed the port from COM 11 to COM 2.
- Click on the OK button to save the settings and close the open windows. You may have to remove and re-attach the device for the new settings to take effect.
Conclusion: If an application is not working because your device is not using a particular COM port number, then you can change the port number very easily in Windows. This is specially useful for older devices and applications that make use of the fewer number of COM ports.