Often used in budget 721 models. If the FTDI driver doesn't work, search for the CH341SER driver 2. Configure the COM Port Once the driver is installed and the plotter is plugged in: Device Manager by right-clicking the Start menu. Look under Ports (COM & LPT) . Your plotter should appear as "USB Serial Port (COMx)". Important:
Obtain a known-working driver (e.g., PCUT721_Win10_x64.zip ). Extract to a folder like C:\721_Driver .