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best_practices.rst

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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

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 <= 5805; port++) {
        PortForwarder.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.