Run the downloaded installer ( CH341SER.EXE or the FTDI executable) as an Administrator.
Because of this internal architecture, your PC requires a specific virtual COM port driver to recognize the USB connection. Without this driver, your computer will flag the plotter as an "Unknown Device," and your software will not be able to send cutting paths. Step 1: Identifying the Correct Driver Chip
Ensure the COM port number is under 10 (ideally 1–4). If it's higher, manually change it in Device Manager under Port Settings > Advanced . 3. Software Setup Rohs 721 Cutting Plotter Driver Pc
The (frequently branded under names like Refine , Mh721 , or Liw ) is a highly popular, budget-friendly vinyl cutter used by sign shops and hobbyists globally . However, because these machines use generic USB-to-Serial chips, finding and installing the correct driver on a modern Windows PC can be a major challenge.
Issue 1: "Device Descriptor Request Failed" or Yellow Exclamation Mark Run the downloaded installer ( CH341SER
Before downloading files, look at your driver package or device manager. The RoHS 721 typically uses one of two common Chinese USB-to-Serial chipsets:
Look for a device labeled "USB Serial Port" or "Unrecognized Device" with a yellow warning triangle. Step 1: Identifying the Correct Driver Chip Ensure
Select MH721 , RoHS 721 , or D721 . (The MH721 profile uses the exact same HP-GL/DMPL language commands and works flawlessly with the RoHS 721).
Incorrect software language command (Using DMPL instead of HPGL) or bad flow control.
To help narrow down any specific connection issues you might be facing, let me know: Which and version are you using? What Windows operating system version is your PC running?
Be extremely cautious when downloading drivers for generic cutters. Many third-party sites bundle malware or adware. Always follow these safe practices: