wrong serial number for FTDI modules ?

[ffred]

Hi, I'm just beginning to use Serialport (a big thank you for your work ! 👍 ) and I notice a difference in the serial number reported, compare to the one reported by FT_Prog (from FTDI) or by USBDeview.

I tried it on Windows 10 & 11, with USB-RS485-PCB & USB-RS232-PCB modules. Serialport always give me the same serial number than FT-PROG / USBDeview, but with an added "A" at the end. for example FTFT5RXY12A instead of FT5RXY12.

not really a problem for me actually, I will use it with the extra "A", but just want to let you know.
thanks.
ffred

[sirhcel]

Thank you for spotting this! I can confirm this behavior by running the example list_ports on both, macOS and Windows.

Interestingly, pyserial also reports an extra a at the end of the serial number on Windows, despite employing a dedicated parsing routine for device identification strings starting with FTDIBUS:

>python -m serial.tools.list_ports --verbose
[...]
COM6
    desc: USB Serial Port (COM6)
    hwid: USB VID:PID=0403:6001 SER=[...]A
2 ports found

The issue was already brought up with pyserial/pyserial#61 and it ended up unresolved. The appended A seems to be produced by the driver stack and is already reported this way by SetupDiGetDeviceInstanceIdA. The Serial number reported by the USB device descriptor does not have the excess A.

A correct serial number seems to be reported by the "parent instance id". We could try to use this one but this would break serial number for users already looking for a certain one. A tough call ...