Fix Maddening FTDI USB Bus Contention Issues on macOS: A Definitive Solution

Updated at: 24/06/2025

Frustrated with FTDI USB bus contention errors crippling your macOS workflow? This definitive guide provides clear, step-by-step solutions to banish these maddening issues for good. We'll explore common causes, from driver conflicts to faulty hardware, and offer practical fixes, including troubleshooting tips and preventative measures. Say goodbye to frustrating delays and hello to seamless USB connectivity.

Step-by-Step Instructions

  1. Identify the Problem

    • Experiencing disappearing or malfunctioning serial ports (Cu.USB Serial) after unplugging and replugging your FTDI board.
    Identify the Problem: Experiencing disappearing or malfunctioning serial ports (Cu.USB Serial) after unplugging and replugging your FTDI board.
    Identify the Problem

  2. Attempt Initial Troubleshooting

    • Try different USB ports or a USB hub before proceeding. If this temporarily fixes the problem but it eventually recurs, continue to step 3.
    Attempt Initial Troubleshooting (Optional but Recommended): Try different USB ports or a USB hub before proceeding. If this temporarily fixes the problem but it eventually recurs, continue to step 3.
    Attempt Initial Troubleshooting

  3. Uninstall FTDI Drivers

    • Uninstall FTDI Drivers (from both locations):
    • Remove drivers from the `/Library/Extensions` directory (as described in the FTDI document).
    • Remove drivers from the `/System/Library/Extensions` directory (this step was crucial for the speaker).
    Remove drivers from the `/System/Library/Extensions` directory (this step was crucial for the speaker). Remove drivers from the `/System/Library/Extensions` directory (this step was crucial for the speaker). Remove drivers from the `/System/Library/Extensions` directory (this step was crucial for the speaker).
    Uninstall FTDI Drivers

  4. Reboot

    • Reboot your macOS computer.
    Reboot your macOS computer.
    Reboot
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Tips

  • Requires root access to remove files from `/System/Library/Extensions`. Instructions for gaining root access are available in the video description.
  • This solution seems effective for macOS systems that have undergone multiple upgrades since Mountain Lion . Older legacy drivers might be causing the conflict.

Common Mistakes to Avoid

1. Incorrect Driver Installation

Reason: Installing the wrong FTDI driver or a corrupted version can lead to bus contention issues and prevent proper device recognition.
Solution: Uninstall any existing FTDI drivers completely and reinstall the correct version from the official FTDI website.

2. Power Issues

Reason: Insufficient power to the USB port or the connected device can cause bus contention, leading to instability and errors.
Solution: Try a different USB port, a powered USB hub, or a higher-powered adapter to ensure sufficient power supply.

3. Conflicting Software or Drivers

Reason: Other applications or drivers might interfere with the FTDI device, causing resource conflicts and bus contention.
Solution: Temporarily disable other applications or drivers that might be using the same USB port or resources to isolate the problem.

FAQs

Why am I getting 'FTDI USB Bus Contention' errors on my Mac?
This error typically arises from a conflict between multiple devices using the same FTDI chip or driver. It could be due to driver issues, faulty hardware (like a failing USB port or device), or even power limitations. Sometimes, simply restarting your Mac can resolve temporary conflicts.
I've tried everything, and the error persists. What else can I do?
If basic troubleshooting (restarting, checking cables, etc.) fails, consider these advanced steps: updating your macOS, reinstalling FTDI drivers (ensure you get the correct ones for your specific chip), using a different USB port or hub (powered hubs are recommended for power-hungry devices), and testing the device on another Mac to rule out hardware problems. If the problem persists, the FTDI device itself might be faulty.