Name: Ucom UC JS704 S Driver
Author: Ucom

Question 1

Driver install fails (Code 10/28)?

Accepted Answer

Disconnect the UC JS704 S, uninstall any existing USB-to-serial driver, reboot, then run the Ucom driver as administrator. If Windows blocks it, use the signed package or temporarily disable driver signature enforcement.

Question 2

Device not detected / no COM port?

Accepted Answer

Try a different USB port directly on the PC, not a hub. Check Device Manager for “Unknown device” or “USB-Serial Controller,” scan for hardware changes, then assign a free COM port under Port Settings.

Question 3

Version conflicts / yellow warning icon?

Accepted Answer

Remove older USB-to-serial drivers via Device Manager with hidden devices shown, then reinstall only the Ucom-matched version. Prevent Windows Update from automatically replacing the working driver.