I'm having similar problems with the Fitlet2. I can't get it work on a fresh Win10 home install with either the drivers on the website or the drivers obtained from Windows Update.
Here's what happens when I install the latest drivers directly from the Fit-PC website. The UART controller drivers do not start, and the sub-devices are not even detected.
- Result of installing drivers directly from Fit-PC website
- Fitlet2ComPortSiteDrivers.png (82.74 KiB) Viewed 9350 times
If I let Windows Update detect the device instead, it installs a completely different driver. These drivers appear to start, but I still need to install the sub-device driver from the Fit-PC website before the COM Ports appear in device manager.
- What is detected in Windows Update
- Fitlet2ComPortWindowsUpdate.png (194.93 KiB) Viewed 9350 times
When I combine the two, device manager looks happy. However, it's not possible to open either COM port in PuTTY. I have other software that detects both ports as "COM 0", despite being listed as COM1 and COM2 in device manager.
- UART drivers from Windows Update, Sub-device drivers from Fit-PC website.
- Fitlet2ComPortSubDevice.png (86.83 KiB) Viewed 9350 times
Note the "on Host Controller 5AC0" on the sub-device, which clearly links it to the UART controller pulled through Windows update. It's also concerning that two serial ports are detected when there only appears to be one implemented in hardware.
This is using the sub-device driver that was uploaded to the website on Friday (2018-08-17). All other device drivers on the system are installed and operational (Chipset, TXE etc.). It doesn't seem to make a difference if the other drivers come from Windows Update or the Fit-PC website (I tried both). Windows 10 Home 1803 was installed using the USB media creation tool.
The two configurations were tried with full HDD wipe and reinstall inbetween. I've also got 4 units here which all exhibit this problem. I don't think it's specific to a single unit.
Update: Just tried Win10 Pro and got exactly the same result.