USB Connection

The NanoVNA-H connects to computers via USB as a virtual COM port (CDC device). This enables remote control, data transfer, and firmware updates.

Hardware Connection

1. Use a USB Type-C cable (NanoVNA-H4) or Micro-USB cable (NanoVNA-H)
2. Connect to your computer’s USB port
3. The NanoVNA-H should power on automatically
4. Wait for device enumeration (a few seconds)

Note

Use a quality USB cable with data lines. Some charging-only cables will not work for data transfer.

Driver Installation

Windows

Modern Windows (10/11) usually installs drivers automatically:

1. Connect NanoVNA-H via USB
2. Windows should automatically install CDC drivers
3. Check Device Manager for “COM & LPT ports”
4. Note the assigned COM port number (e.g., COM3)

If automatic installation fails:

1. Open Device Manager
2. Find the unknown device (usually under “Other devices”)
3. Right-click and select “Update driver”
4. Choose “Search automatically for drivers”

For Windows 7/8, you may need to install the STM32 Virtual COM Port driver manually from ST Microelectronics.

Linux

Linux includes CDC-ACM drivers by default:

1. Connect NanoVNA-H via USB
2. The device appears as /dev/ttyACM0 (or similar)
3. Check with: ls -la /dev/ttyACM*
4. Verify with: dmesg | tail -20

Permissions

You may need permission to access the serial port:

# Add user to dialout group (Debian/Ubuntu)
sudo usermod -a -G dialout $USER

# Or on Arch/Fedora
sudo usermod -a -G uucp $USER

# Log out and back in for changes to take effect

Or create a udev rule for permanent access:

/etc/udev/rules.d/70-nanovna.rules

SUBSYSTEM=="tty", ATTRS{idVendor}=="0483", ATTRS{idProduct}=="5740", MODE="0666"

# Reload udev rules
sudo udevadm control --reload-rules

macOS

macOS includes CDC drivers:

1. Connect NanoVNA-H via USB
2. The device appears as /dev/tty.usbmodemXXXX
3. List available ports: ls /dev/tty.usb*

Verify Connection

Using Terminal Software

1. Open terminal software (PuTTY, screen, minicom)
2. Connect to the COM port at 115200 baud
3. Press Enter to see the prompt ch>
4. Type help to see available commands

Using Python

import serial

# Connect (adjust port name for your OS)
ser = serial.Serial('/dev/ttyACM0', 115200, timeout=1)

# Send command
ser.write(b'help\r\n')

# Read response
response = ser.read(1000)
print(response.decode())

ser.close()

Connection Parameters

Parameter	Value
Baud rate	115200 (default, adjustable)
Data bits	8
Stop bits	1
Parity	None
Flow control	None

Tip

The actual baud rate doesn’t matter for USB CDC connections - the USB protocol handles the speed. Most software uses 115200 by convention.

Troubleshooting

Device Not Recognized

• Try a different USB cable
• Try a different USB port
• Check if NanoVNA powers on (display active)
• On Windows, check Device Manager for errors
• On Linux, check dmesg output

Permission Denied (Linux)

# Check device permissions
ls -la /dev/ttyACM0

# Temporary fix
sudo chmod 666 /dev/ttyACM0

# Permanent fix: add user to dialout group
sudo usermod -a -G dialout $USER

Multiple COM Ports

If you have multiple USB serial devices:

• Note which port appears when you plug in the NanoVNA-H
• Use device manager or dmesg to identify the correct port
• Disconnect other USB serial devices temporarily

Communication Errors

• Ensure no other software is using the port
• Close any terminal sessions before opening new ones
• Try disconnecting and reconnecting the USB cable
• Restart the NanoVNA-H

Serial Console vs Hardware Serial

The NanoVNA-H firmware can use either:

• USB CDC: Virtual COM port over USB (default)
• Hardware UART: Physical serial pins (if enabled)

The VNA_MODE_CONNECTION flag determines which is active. USB CDC is normally used for PC communication.

Caution

Only one application can access the COM port at a time. Close other software before connecting.

Next Steps

Once connected, you can:

• Use the Serial Console for direct command access
• Connect NanoVNASaver or NanoVNASharp for graphical control
• Enable Remote Desktop mode for display streaming