How long does it take for a PC to recognize a CP210x device after it is plugged into a USB port?
The enumeration time of a USB device depends on the system. Different operating systems will issue a varying number of requests during enumeration which can lengthen the time before a device is ready to be opened by the PC application.
The first time that a device is connected to PC typically takes longer as the operating system has to load the driver for the device. Subsequent connections should enumerate a device in one to two seconds, but applications should not be designed to assumed a fixed amount of time. Any application that connects to a CP210x device should wait for enumeration to complete before attempting to open the handle.