How to Install the CH340 Driver for GRBL CNC and Laser Engravers

A CH340 or CH341 driver problem can prevent Windows or macOS from creating the virtual COM port that Candle, LaserGRBL, or LightBurn needs to send G-code. The fix is usually a combination of installing the correct USB-to-serial driver, confirming that the operating system recognizes the machine, selecting the assigned port, and setting the software to 115200 Baud.

This guide covers CH340 driver installation for 32-bit GRBL CNC routers and diode laser engravers, including TwoTrees machines. It does not cover CAD design, cutting parameters, or feeds and speeds.

What the CH340 driver does

The CH340 is a USB-to-UART bridge on the machine’s GRBL control board. Your computer communicates through USB, while the controller receives serial data through a TTL UART interface. The CH340 converts the computer’s USB data into the serial communication that the GRBL board uses to receive commands such as G-code.

The driver is the software layer that allows the operating system to communicate with this bridge. Once the driver is working, Windows or macOS can create a virtual serial port. Control software then uses that port to connect to the GRBL controller.

If the driver is missing, blocked, or conflicting with another driver, the machine may receive power but remain unavailable to the control software.

Before installing anything, connect the machine with a known data-capable USB cable and turn the machine’s power supply switch on. Use a direct connection to the computer whenever possible. A standard USB-A to USB-B or USB-C data cable is required; a charge-only cable cannot carry the serial data needed for a connection.

Download the appropriate files from the TwoTrees Official Software & Driver Center.

Install CH340 on Windows

On Windows 10 and Windows 11, common symptoms include “Port not found” in control software or a yellow exclamation mark beside the device in Device Manager.

1. Download the driver

Download the Windows CH340 or CH341 driver package supplied for your machine. The installer may be named CH341SER.EXE.

Use the driver supplied by the machine manufacturer or another trusted source. Avoid installing several unrelated USB-to-serial driver packages at the same time because competing drivers can make diagnosis more difficult.

2. Run the installer as administrator

1. Close Candle, LaserGRBL, LightBurn, and any other program that may be using a serial port.

2. Locate CH341SER.EXE in your downloaded files.

3. Right-click the installer.

4. Select Run as administrator.

5. Follow the installer prompts.

6. Restart Windows if the installer requests it.

After installation, reconnect the USB cable directly to the computer. If the machine was already connected during installation, disconnecting and reconnecting it allows Windows to enumerate the device again.

3. Confirm the COM port

Open Device Manager:

1. Right-click the Windows Start button.

2. Select Device Manager.

3. Expand Ports (COM & LPT).

4. Look for an entry associated with the CH340, CH341, USB-SERIAL device, or the connected GRBL controller.

The entry should display a port assignment such as COM3 or COM5. Note the number because you will select the same port in your control software.

A yellow exclamation mark indicates that Windows has detected a device but has not initialized it correctly. Right-click the device and review its properties for an error message. If necessary, uninstall the problem device, disconnect the machine, restart Windows, and reinstall the manufacturer-supplied driver before reconnecting it.

Do not remove unrelated devices at random. A driver conflict should be corrected by identifying the affected USB-to-serial device first.

Install CH340 on macOS

On macOS, the machine may appear to connect and then disconnect, or the serial device may not appear in LightBurn, LaserGRBL, or another GRBL application. macOS security controls can block a CH34x driver or its system extension even after the package has been installed.

The exact labels can vary slightly between macOS versions, but the process follows this sequence.

1. Install the driver package

Download the macOS CH34x driver package, such as CH34xVCP.pkg, from the manufacturer’s software and driver resources.

1. Close all CNC and laser-control software.

2. Open the downloaded package.

3. Follow the installation prompts.

4. Restart the Mac if requested.

Keep the machine’s USB connection direct during testing. If the Mac does not recognize the device, remove any hub from the connection path before continuing.

2. Authorize the system extension

After installation, open:

System Settings > Privacy & Security

Look for a message stating that software or a system extension from the CH34x driver was blocked. If macOS presents an Allow option, authorize the driver according to the on-screen instructions. You may need to authenticate with the Mac’s administrator password and restart the computer.

If no authorization message appears, restart the Mac with the machine disconnected, then reconnect the machine and check Privacy & Security again. Do not bypass unrelated security controls or install a driver from an unknown source.

3. Check whether the serial device appears

Reconnect the powered machine directly to the Mac and open your control software. The device may appear under a name such as:

• /dev/cu.wchusbserial...

• /dev/cu.usbserial...

Select the port that appears when the machine is connected. If it disappears when the USB cable is removed and returns when the cable is reconnected, that is a useful indication that you have identified the machine’s serial device.

If the port never appears, check the cable, USB adapter, driver authorization, and direct connection before changing software settings.

Configure GRBL software at 115200 Baud

Installing the driver creates the operating-system port, but the control program still needs the correct port and communication speed.

For 32-bit GRBL machine communication, TwoTrees documentation specifies a communication speed of 115200 Baud. A mismatch can cause failed connections, immediate disconnections, or unreadable characters in the console. TwoTrees FAQs

LightBurn

In LightBurn:

1. Connect the powered machine to the computer.

2. Open Devices or the machine connection controls.

3. Select the detected serial or GRBL device.

4. Choose the COM port shown by Windows or the serial device shown by macOS.

5. Set the connection speed to 115200 if LightBurn provides a manual Baud Rate field.

6. Connect to the machine.

If LightBurn cannot find the port, close it, verify the port in the operating system, and reopen LightBurn. Another program may already have the port open.

LaserGRBL

In LaserGRBL:

1. Open the serial connection controls.

2. Select the CH340-assigned COM port on Windows or the detected serial device on macOS.

3. Set the Baud Rate to 115200.

4. Connect to the machine.

5. Check the console for a normal GRBL response rather than random or unreadable characters.

LaserGRBL should not be connected at the same time as LightBurn or another serial-control program. Only one application should use the GRBL serial port at a time.

Candle

In Candle:

1. Open the connection or controller settings.

2. Select the COM port assigned to the machine.

3. Set the Baud Rate to 115200.

4. Connect to the controller.

5. Confirm that the console responds normally before sending a job.

The port name varies by operating system, but the communication speed must match the GRBL controller’s expected setting.

Diagnose a missing or unstable port

Work through the physical connection before changing drivers repeatedly. The following sequence isolates the most common causes.

Check the USB cable

A cable can power a machine without carrying data. Replace a suspected cable with a known USB data cable that matches the machine’s connector.

Avoid assuming that a cable is suitable because the machine powers on. Power and data use different conductors inside the cable.

Remove unpowered USB hubs

Connect the machine directly to the computer. Unpowered splitters and hubs can interfere with device detection or provide an unreliable connection, particularly when other USB devices are attached.

If a direct connection works but a hub does not, keep the machine directly connected or use a properly powered hub that is compatible with the computer and cable arrangement.

Confirm that the machine is powered

For port-detection testing, turn on the machine’s power supply switch before checking for the serial device. USB connection behavior can vary when the controller is not fully powered.

Do not confuse the presence of a USB device with proof that the machine is ready to move. Confirm the machine’s normal operating state before sending commands.

Check for another program using the port

Close LightBurn, LaserGRBL, Candle, firmware tools, terminal programs, and other applications that may have opened the same serial port. A port generally cannot be controlled normally by multiple applications at once.

After closing the other software, disconnect and reconnect the machine, then reopen only the program you intend to use.

Resolve a driver conflict

On Windows, revisit Device Manager and inspect the device listed under Ports (COM & LPT) or under an unknown-device category. If the device has an error symbol, review its properties and remove only the affected device entry if a clean reinstall is necessary.

On macOS, check Privacy & Security for a blocked CH34x system extension. Reinstalling the package without authorizing the blocked extension may leave the underlying problem unchanged.

Try a different physical USB port

A different USB port can help distinguish a port-specific issue from a machine or driver issue. Connect directly to the computer, avoid adapters where possible, and wait for the operating system to enumerate the device before opening the control software.

Recognize Baud Rate symptoms

A Baud Rate problem is different from a missing driver.

• If no serial port appears in the operating system, begin with the cable, power, driver, permissions, and USB connection.

• If the port appears but the software reports that it cannot connect, verify that the selected port is correct and that another application is not using it.

• If the software connects but the console displays gibberish or unreadable characters, check the Baud Rate and set it to 115200.

• If the connection works briefly and then drops, inspect the cable, hub, driver authorization, and physical USB connection before assuming the GRBL board is defective.

Do not change unrelated machine settings to solve a communication problem. Establish a stable serial connection first.

Protect the controller during firmware work

Driver installation and ordinary G-code communication are separate from firmware updating. If you are writing firmware to the mainboard, do not unplug the USB cable or cycle the machine’s main power while the update is in progress. Interrupting a firmware write can leave the controller unusable.

Complete driver installation, port selection, and communication testing before starting a firmware procedure. Follow the instructions for the exact controller and firmware package rather than applying steps from a different machine.

When the connection is ready

The connection is ready for normal GRBL control when:

• The CH340 or CH341 device appears without an operating-system error.

• You can identify the assigned COM port or macOS serial device.

• The machine remains connected after opening the control software.

• The software uses the correct port.

• The Baud Rate is set to 115200.

• The console displays normal controller communication rather than unreadable characters.

For TwoTrees users, the TTC450 Pro CNC Router and TS2 and TTS Series laser engravers require the same practical connection checks described here: a working CH340-compatible driver, a direct USB data connection, the correct operating-system port, and compatible GRBL communication settings. The exact machine, board, cable connector, and software workflow still determine which port name and connection controls appear.

If the port remains unavailable after these checks, consult the TwoTrees Official Help Center for model-specific driver files and connection procedures.

References

1. TwoTrees Help Center

2. TwoTrees FAQs