How do I determine CP2105 COM Port Numbers in Windows?
Once the device has enumerated, Windows will assign the CP2105 two COM port numbers. Here are a couple of ways to look for the COM port numbers.
Manual Method — You can manually check for device enumeration in the Windows Device Manager. The CP2105 will show up as two COM port numbers like below. Note: If you are using a customized driver, the device may not be listed as "Silicon Labs Dual CP210x...", but it will still have COM port numbers.
Programmatic Method — Windows stores the COM port numbers in the Windows registry. Software can be written to search the registry for these COM port numbers. See Application Note AN197 section 7 for details.