Best Practices

Event Preparation Checklist

• Download and backup all pipelines to your programming laptop.
• Download a copy of the latest Limelight image to your programming laptop.
• Record a list of your pipelines and their indices.
  • 1 - Dual Target Low
  • 2 - Dual Target High Cargo
• Add strain reliefs to all power and ethernet cables going to your LL.
• Consider hot-gluing all connections.
• Make sure you are using a dashboard (Smartdashboard, Shuffleboard) and not a web browser to view the stream while practicing and during events. Default web controls don't have the ability to auto-reconnect to streams after spurious disconnections, but SmartDashboard and Shuffleboard both have auto-reconnection built-in by default.
• Add a network switch to your robot to enable ethernet tethering while at an event and to avoid the second radio port. We recommend the Brainboxes SW-005 5 port Switch
• Use twisted Cat6 cables with stranded wires. Do not use flat ethernet cables.
• Do not use the second radio port. Route all devices through your network switch if possible.
• Setup Port Forwarding to enable Limelight communication while tethered to your robot over USB.
  • Forward ports 5800, 5801, 5802, 5803, 5804, 5805, 5806, and 5807

Java

    import edu.wpi.first.wpiutil.net.PortForwarder;
    @Override
    public void robotInit() 
    {
        // Make sure you only configure port forwarding once in your robot code.
        // Do not place these function calls in any periodic functions
        for (int port = 5800; port <= 5809; port++) {
            PortForwarder.add(port, "limelight.local", port);
        }
    }

http://roborio-(teamnum)-FRC.local:5801 will now forward to limelight.local:5801

To add a second limelight, use a different set of local ports. Note the "+10" in the first PortForwarder.add() argument:

        for (int port = 5800; port <= 5809; port++) {
            PortForwarder.add(port+10, "limelight-left.local", port);
        }

http://roborio-(teamnum)-FRC.local:5811 will now forward to limelight-left.local:5801

C++

    #include <wpi/PortForwarder.h>
    void Robot::RobotInit 
    {
        for (int port = 5800; port <= 5809; port++)
        {
            wpi::PortForwarder::GetInstance().Add(port, "limelight-left.local", port);
        }
    }
    

http://roborio-(teamnum)-FRC.local:5801 will now forward to limelight.local:5801

To add a second limelight, use a different set of local ports. Note the "+10" in the first PortForwarder::add() argument:

    for (int port = 5800; port <= 5809; port++)
    {
        wpi::PortForwarder::GetInstance().Add(port+10, "limelight.local", port);
    }

http://roborio-(teamnum)-FRC.local:5811 will now forward to limelight-left.local:5801

After port forwarding is enabled, you may access your Limelight's config page at http://roborio-(teamnum)-FRC.local:5801. For example, team 2928 would use http://roborio-2928-FRC.local:5801

During Event Calibration

• Roll your robot to each target on the field.
  • Make sure your thresholding is working properly. Switch to the "threshold" view during this process (located under the image stream).
  • Roll your robot close to the target, and far away from the target. Ensure crosshairs are calibrated properly.
  • While far away from the target, rotate your robot left and right ~ 30 degrees to ensure that other targets will not be erroneously tracked.
  • See the tuning section below for more tuning tips.
  • Ensure no other field / arena elements are being accidentally tracked. Check your area and aspect ratio filters if you are picking up arena lights.
  • Take snapshots of all targets and erroneous targeting. You can use these to tune your pipelines in the pits.

Pipeline Tuning

• Use the lowest exposure possible, and increase black level offset until field lights and LED reflections are removed from the image.
• Test your thresholding while far away and angled away from your target.
• Use 2019.7's "Smart Speckle Rejection" to filter unwanted LED reflections

Before Connecting to the Field

• Give your laptop a static IP configuration.
  • IP: 10.TE.AM.5
  • Subnet Mask: 255.0.0.0
  • Gateway: 10.TE.AM.1
• Give your RIO a static IP configuration.
  • IP: "10.TE.AM.2"
  • Subnet Mask: 255.255.255.0 <- NOTE THE DIFFERENCE HERE
  • Gateway: 10.TE.AM.1
• Give your Limelights unique hostnames (if using multiple).
• Give your Limelights unique static IP configurations.
  • Always start with ".11" addresses and go upward. (10.9.87.11, etc.)
  • The use of other addresses may cause your units to malfunction when connected to the FMS.
  • IP: "10.TE.AM.11"
  • Subnet mask: 255.255.255.0
  • Gateway: "10.TE.AM.1"

Note: Teams with zeros need to pay special attention:

- _Team 916 uses 10.9.16.xx,_
- _Team 9106 uses 10.91.6.xx_
- _Team 9016 uses 10.90.16.xx_

Additional information: https://docs.wpilib.org/en/stable/docs/networking/networking-introduction/ip-configurations.html

Pre-Match Checklist

• Check all power and Ethernet cables going to your Limelights.
• Check all electrical connections for looseness and frayed wires.
• Check all mounting screws / zipties / tape.
• Observe ESD precautions at all times.

Bandwidth

• Some teams run two Limelights with two USB cameras while staying well under under the bandwidth limit. Follow the steps below to reduce bandwidth.
• Rather than using driver mode, create a "driver" pipeline. Turn down the exposure to reduce stream bandwidth.
• Using a USB camera? Use the "stream" NT key to enable picture-in-picture mode. This will dramatically reduce stream bandwidth.
• Turn the stream rate to "low" in the settings page if streaming isn't critical for driving.
• Use the 160x120 stream option introduced in 2019.7.

Troubleshooting

• Try to access the stream at IP:5800 with a web browser. This should help you determine the root of your issues.
• Restart your dashboard
• Reboot your computer
• Reboot your robot if the field has been reset
• Broken Ethernet cables can be the cause of intermittent networking issues.
• Always use static IP configurations on the field.