The CP210x USB-to-UART Chipset
The Rabbit Board 4-Axis uses a Silicon Labs CP210x USB-to-UART bridge to communicate with a computer through its USB connection. The operating system normally detects this chipset and creates a virtual serial port, shown as a COM port on Windows.
If the Rabbit Board is connected but does not appear in your CNC control software or in the operating system serial port list, the required CP210x Virtual COM Port driver may not be installed.
Download the Official Driver
Download the official CP210x USB-to-UART Bridge VCP Driver directly from Silicon Labs:
Download the CP210x VCP Driver from Silicon Labs
Select the driver that matches your operating system. For current Windows systems, use the CP210x Universal Windows Driver listed on the official download page.
Install the Driver and Reconnect the Board
Install the downloaded driver by following the instructions provided with the driver package. When installation is complete, disconnect the Rabbit Board from USB and connect it again. Restart the computer if the installer requests it.
On Windows, open Device Manager and check the Ports (COM & LPT) section. The CP210x device should appear as a Silicon Labs CP210x USB-to-UART Bridge with an assigned COM port. Select this COM port in Focus or your preferred GRBL-compatible G-code sender.
If the Board Is Still Not Detected
If the serial port still does not appear, confirm that the USB cable supports data transfer, try another USB port, and avoid unpowered USB hubs. Also verify that the Rabbit Board is powered correctly.
Try a different high-quality shielded USB cable, preferably no longer than 1.8 meters. If Windows displays an unknown USB device, remove that device from Device Manager, reconnect the Rabbit Board, and reinstall the official Silicon Labs driver.