Activity 4.10: Explore Live NetworkTables

🎯 Goal

By the end of this activity you will have:

• Connected to a running robot (or simulation) and viewed live NetworkTables data
• Identified at least 10 NetworkTables entries and traced where they come from in the code
• Documented the tables, keys, and value types your robot publishes
• Found the Limelight entries and autonomous chooser in the NetworkTables tree

Before You Start

Complete Lesson 4.9: NetworkTables Basics first. You need a running robot or a WPILib simulation to see live data. If you don’t have access to the robot right now, you can run the robot code in simulation mode — ask your mentor or lead programmer for help with Simulate Robot Code in VS Code.

---

Choose Your Tool

You’ll use one of these tools to browse NetworkTables. Pick whichever is available:

Tool	How to Open	Best For
OutlineViewer	WPILib VS Code → Command Palette → “Start Tool” → OutlineViewer	Simple text-based browsing of all entries
AdvantageScope	Download from docs.advantagescope.org → connect to robot IP	Rich visualization with graphs and 3D views
Shuffleboard	WPILib VS Code → Command Palette → “Start Tool” → Shuffleboard	Widget-based dashboard view

For this activity, OutlineViewer or AdvantageScope are recommended because they show the raw NetworkTables tree — every table, every key, every value.

---

Step 1: Connect to the Robot

1. Make sure the robot is powered on and connected to your computer (via USB, Ethernet, or WiFi)
2. Open your chosen tool
3. Connect to the robot’s IP address:
   • USB: 172.22.11.2
   • WiFi/Ethernet: 10.TE.AM.2 (replace TE.AM with your team number, e.g., 10.17.23.2)
   • Simulation: localhost or 127.0.0.1

Once connected, you should see a tree of tables and entries populate. If nothing appears, check that the robot code is running (the Driver Station should show “Communications” green).

---

Step 2: Explore the SmartDashboard Table

Expand the SmartDashboard table. This is where most of your team’s published data lives. You should see entries like:

• Motor speeds and sensor readings from subsystem periodic() methods
• The autonomous chooser (look for “Auto Chooser” or similar)
• Any custom values your team publishes for debugging

Document at least 5 SmartDashboard entries:

Key	Value (current)	Type	Where in Code?
Example: Intake/Speed	0.0	Double	IntakeSubsystem.periodic()

For the “Where in Code?” column, search your project for the key name (e.g., search for "Intake/Speed") to find the SmartDashboard.putNumber() call that publishes it.

---

Step 3: Find the Limelight Table

Look for a table called limelight (or limelight-front, limelight-back if your team has multiple cameras). Expand it and find these key entries:

Key	What It Means	Current Value
tv	Target visible (0 = no, 1 = yes)
tx	Horizontal offset to target (degrees)
ty	Vertical offset to target (degrees)
ta	Target area (% of image)
botpose_wpiblue	Robot pose estimate from AprilTags

Try pointing the Limelight at an AprilTag and watch the values change in real time. The tv value should flip from 0 to 1, and tx/ty should show the offset.

▶What if I don't see a limelight table?

If there’s no limelight table, the Limelight camera might not be connected or powered. Check:

1. Is the Limelight plugged into the robot’s network switch?
2. Can you access the Limelight web interface at http://limelight.local:5801?
3. Is the Limelight powered? (Check the LED indicator)

If you’re running in simulation, the Limelight won’t be present — that’s expected. Focus on the SmartDashboard and other tables instead.

---

Step 4: Find the FMSInfo Table

Look for a table called FMSInfo. This contains match information published by the Field Management System (or the Driver Station in practice mode):

Key	What It Means
IsRedAlliance	Whether the robot is on the red alliance
MatchNumber	Current match number
EventName	Name of the event
GameSpecificMessage	Game-specific data (varies by year)

These values are read-only — they come from the FMS, not your robot code. Your code can read them using DriverStation.getAlliance() and similar methods.

---

Step 5: Watch Values Change

Now for the fun part. With the NetworkTables viewer open:

1. Enable the robot in teleop (with the Driver Station)
2. Move the joysticks — watch drivetrain-related values change
3. Press a button — watch subsystem values change (intake speed, shooter RPM, etc.)
4. Disable the robot — watch values return to zero or default states

This real-time view is exactly what your drive team sees on the dashboard during a match. Understanding what data is available helps you build better dashboards and debug problems faster.

✅Checkpoint: NetworkTables Exploration

Answer these questions based on your exploration: (1) How many total NetworkTables entries does your robot publish? (roughly) (2) Which table has the most entries? (3) Find one entry that you didn't expect — what is it and where does it come from?

▶Check Answer

Answers will vary by team, but common observations:

1. Total entries: Most FRC robots publish 50–200+ NetworkTables entries. The drivetrain alone can publish dozens (module states, odometry, speeds).

2. Most entries: Usually SmartDashboard or the drivetrain-related table. CTRE’s swerve drivetrain publishes a lot of telemetry data automatically.

3. Unexpected entries: Common surprises include CTRE’s automatic telemetry (module states, odometry), WPILib’s built-in entries (like /LiveWindow/ data), or FMS data you didn’t know was available.

---

Step 6: Document Your Findings

Create a summary of your robot’s NetworkTables landscape:

Table Name	# of Entries	Purpose	Published By
SmartDashboard		Team-published data	Subsystem periodic(), RobotContainer
limelight		Vision camera data	Limelight hardware
FMSInfo		Match/event info	Field Management System

Save this document — it’s a reference for when you need to find specific data for debugging or dashboard building.

---

📖 Key Vocab Used in This Activity

• NetworkTables — the WPILib publish/subscribe communication system connecting robot code, dashboards, and coprocessors
• Publish/Subscribe — the pattern where code publishes data to a topic and other code subscribes to receive updates
• SmartDashboard — a WPILib dashboard class that provides simple methods to send and display data via NetworkTables

What’s Next?

You’ve now seen the data layer that connects your robot to the outside world. Every value on the dashboard, every Limelight reading, and every auto selection flows through NetworkTables.

In Lesson 4.11: FRC Game Manual for Programmers, you’ll shift from code to rules — learning the parts of the FRC Game Manual that directly affect how you write robot code, from autonomous constraints to safety rules.

In Lesson 4.11: FRC Game Manual for Programmers, you’ll shift from code to rules — learning the parts of the FRC Game Manual that directly affect how you write robot code, from autonomous constraints to safety rules.