Best Practices¶

Before An Event¶

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 Branboxes SW-005 5 port Switch
Use twisted Cat6 cables with stranded wires. We do not recommend the use of flat ethernet cables.
We do not recommend use of 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, and 5805

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 <= 5805; port++) {
        PortForwarder.add(port, "limelight.local", port);
    }
}

#include <wpi/PortForwarder.h>
void Robot::RobotInit
{
    for (int port = 5800; port <= 5805; port++) {
        wpi::PortForwarder::GetInstance().Add(port, "limelight.local", port);
    }
}

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

Before Every Match¶

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.