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Limelight 4 Quick-Start

Hardware Specifications​

  • Footprint: 3.154in x 1.894in (80.11mm x 48.11mm)
  • Thickness: 1.160in (29.46mm)
  • Mass: 0.3 lb
  • #10 / M4 Thru-Hole Mounting
  • M3 Threaded mounting holes
  • Power Input: Buck-Boost with 5V-26V Operation (3.5V - 35V absolute maximum)
    • Enhanced transient suppression for robotics applications
    • 12W maximum power consumption
  • Sensor: OV9281 Global Shutter Monochrome (1280x800 @ 120FPS, 640x400 @ 240FPS)
    • IMX462 Back-Illuminated Upgrade Kit coming soon.
  • Replaceable M12 Lens
    • 82 deg Horizontal FOV, 56.2 deg Vertical FOV
  • Black-Anodized, All-Aluminium Enclosure
  • Gigabit Ethernet RJ45 Port (POE is no longer supported)
  • Weidmuller Power Input Port
  • USB C Imaging and Connectivity Port
  • Internal IMU
  • Hailo 8 AI Accelerator support with internal M.2 A+E Key Port.

Software Specifications (Limelight OS)​

  • Plug-and-Play high-performance vision. No experience required.
  • Self-hosted browser-based UI for vision pipeline configuration
  • REST/HTTP, Websocket, NetworkTables, ModbusTCP, and ROS support
  • USB connectivity with plug-and-play USB-Ethernet Driver support on Windows, Linux, MacOS, and Android
  • Drag-and-Drop 20FPS MobileNetSSD object detector neural network support (CPU Inference)
  • Drag-and-Drop 80FPS YoloV8 object detector neural network support (Requires Hailo-8)
  • Configurable Fixed exposure, sensor gain, resolution, and framerate.
  • Configure 10 Hot-swappable Vision Pipelines:
    • Custom Python Pipelines with OpenCV 4.10, numpy, etc.
    • 2D, 3D AprilTag Tracking and Robot Localization
      • Full 3D Localization (Robot GPS) with MegaTag1
      • Full 3D Localization (Robot GPS) with IMU Fusion with MegaTag2
      • Up to 240FPS performance with detector Downscaling
      • Full 3D Visualizer in web interface
    • 120-240FPS Color Blob pipelines
    • Neural Object Detection Pipelines
    • Neural Image Classification Pipeliens
    • Barcode Tracking Pipelines
    • Lens Focusing Pipeline
    • Viewfinder pipeline for low-latency streaming
  • Built-in Charuco Intrinsics Calibration interface for high-accuracy vision pipelines.
  • Intrinsics Calibration visualization
  • Built-in low-latency MJPEG Streaming. Configurable stream orientation

1. Mounting Limelight 4​

Thru-Hole Mounting​

  • Use 1 1/4" #10-32 or #10-24 screws with nylock nuts
  • Alternatively, use 38mm M4 bolts with nylock nuts
  • Use plastic washers to preserve anodization

Threaded Mounting (Backside)​

  • 2x M3 threaded mounting points
  • Consider light application of threadlocker

Limelight 4 Drawing

2. Wiring Limelight 4​

Power​

Limelight 4 Hero Shot

Ethernet​

  • Run an ethernet cable from your Limelight to your robot radio
  • Use twisted Cat6 cables with stranded wires (ideally 20AWG)
  • Add a strain relief to your ethernet cable
  • POE is no longer supported

USB Flashing​

  • To enter flash mode, hold the configuration while plugging-in over USB C
  • While flashing, it is safe to power Limelight 4 over USB.

USB-Ethernet Interface​

  • Limelight 4 has USB-Ethernet funcitonality that allows for plug-and-play connectivity with Windows, Linux, and MacOS. You can use the web interface and all other features over USB.
  • While using this interface, Limelight 4 will exceed the power rating of most USB ports. It is recommended to power Limelight 4 via the weidmuller port while using USB-Ethernet.
  • Limelight 4 configuration UI on Windows (USB-Ethernet): http://172.28.0.1:5801
  • Limelight 4 configuration UI on Linux (USB-Ethernet): http://172.29.0.1:5801

3. Accessing the Web Interface​

After connecting your Limelight 4 to your network:

  1. Power up your robot and connect your laptop to your robot's network
  2. Use one of these methods to access the web interface:
    • Method 1: Open the Limelight Hardware Manager application, scan for Limelights, and double-click on your Limelight when it appears
    • Method 2: Open a web browser and navigate to http://limelight.local:5801
    • Method 3: Open a web browser and navigate to your Limelight's static IP address with port 5801 (if configured)
    • Method 4 (USB): Connect via USB-C and navigate to:

Once connected, you'll have access to:

  • Settings tab - Configure team number, hostname, and other system settings
  • Vision Pipeline tabs - Set up and tune your vision processing pipelines
  • Camera & Crosshair tab - Adjust camera settings and crosshair parameters
  • 3D Visualization tab - View real-time AprilTag detection and localization

All configuration is done through this web interface. Changes are saved automatically to your Limelight.

4. Updating LimelightOS​

注意

Backup your pipelines and scripts before upgrading - they will be erased during this process!

  1. Power off your Limelight
  2. Download the latest USB drivers/RPIboot, Limelight OS image, and Balena Flash tool
  3. Hold the config button while connecting a USB-C cable from your laptop to your Limelight
  4. Run "rpiboot-CM4-CM5 - Mass Storage Gadget" from the Windows start menu

Run rpiboot utility

You should see the following if RPIBoot has successfully mounted your Limelight. Rpiboot success

If you see anything else, remove the USB Cable, re-press the button, reinsert the usb cable, and restart the rpiboot utility.

  1. Run "Balena Etcher" as administrator
  2. Click "Flash From File" and select the latest .zip image
  3. Click "Select Target" and choose "mmcblk0 USB Device" in the "Drives" menu
  4. Click "Flash" and wait for completion

Balena Etcher flashing OS

  1. Remove the USB cable when done

5. Focusing Your Limelight 4 (ethernet only)​

  1. Power-on your robot.
  2. Connect to the web interface as descirbed in section 3
  3. Click the "Ignore NT pipeline index" to enable pipeline switching, and switch to pipeline 9
  4. Set the pipeline type to "focus"
  5. Go to the configuration tab, and increase stream quality to maximum
  6. Make sure the camera is pointed at something with lots of features and contrast, such as an ARUCO board, a detailed scene, or a siemen's star
  7. Turn the lens to maximize the on-screen focus score
  8. Once focused, apply 3-8 dots of super glue or super glue gel around the lens

6. Network Configuration​

Setting the Team Number (Required for FRC / Networktables)​

  1. Power up your robot and connect your laptop to your robot's network
  2. Open the Limelight Hardware Manager, scan for Limelights, and double click the entry that appears.
  3. Alternatively, navigate to http://limelight.local:5801
  4. Go to the "Settings" tab
  5. Enter your team number and press "Update Team Number"

Setting a Unique Hostname (Only Required for FRC / Networktables systems with multiple Limelights)​

  1. If you are using multiple Limelights, each Limelight must have a unique hostname
  2. In the settings tab, configura a hostname and click the "set hostname" button.
  1. Change "IP Assignment" to "Static"
  2. Set IP address to "10.TE.AM.11"
    • Team 916 uses 10.9.16.xx
    • Team 9106 uses 10.91.6.xx
    • Team 9016 uses 10.90.16.xx
  3. Set Netmask to "255.255.255.0"
  4. Set Gateway to "10.TE.AM.1"
  5. Click "Update"
  6. Power-cycle your robot
  7. Access your config panel at 10.TE.AM.11:5801 and camera stream at 10.TE.AM.11:5800
  8. If you are using multiple Limelights, give each Limelight a unique static IP address. Gateways and netmasks should be the same across Limelights.
Q. Why do we recommend the use of a static IP address?

A. It multiple seconds off Limelight’s boot time. Second, teams have historically had issues with DHCP assignment and mDNS responders on actual FRC fields and with event radio firmware.

We recommend setting static IP addresses on your robo-rio and driverstation as well. The networking settings to use on all of these devices can be found near the bottom half of this web page

7. Hailo AI Accelerator Module Installation (Optional)​

If you have the optional Hailo AI accelerator module, follow these steps to install it:

  • Attach the included thermal pad to the Hailo SOC (System on Chip)
  • Use the included 1.5mm Allen wrench to remove the three 8mm M2 enclosure screws
  • Set these screws aside (they have threadlocking material)
  • Carefully open the enclosure (note: the camera cable will limit how far you can open it)
  • Insert the Hailo module into the appropriate slot
  • No screws are required to secure the Hailo module
  • Reattach the enclosure using the original three 8mm M2 screws
  • After installing the Hailo module, make sure to update to the latest version of LimelightOS.

8. Troubleshooting​

Status Bar Indicators​

  • Slow Cylon (Scanning): No targets detected by the current pipeline
  • Fast Cylon (Scanning): Targets detected by the current pipeline
  • Slow Alternating LED Blink: Hardware error (camera cable disconnected, sensor damage, etc.)

If limelight.local:5801 doesn't work​

  • Check if you have Bonjour installed (Windows: add/remove programs)
  • Uninstall "bonjour print services" if you have two Bonjour items
  • Install Bonjour from the Downloads page if missing

Reset IP address​

  • Hold the config button for 10 seconds after your Limelight has booted
  • Networking configuration will reset to dynamic addressing on next boot