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Documentation Index

Fetch the complete documentation index at: https://mintlify.com/spectrum3847/2026-Spectrum/llms.txt

Use this file to discover all available pages before exploring further.

This page collects practical advice from Spectrum’s 2026 season development experience — patterns that improve code quality, reduce bugs, and make the codebase easier to work on as a team.

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DoubleSupplier vs double

For most command factories and trigger factories in the Mechanism class, prefer DoubleSupplier arguments over raw double values.
Prefer DoubleSupplier for dynamic values
// Static double — value is locked in when the command is created
Command runAtFixed = launcher.velocityCommand(() -> 3000.0);

// DoubleSupplier — value is evaluated fresh each time the command runs
TuneValue tuneVelocity = new TuneValue("Launcher/Velocity", 3000.0);
Command runAtTunable = launcher.velocityCommand(tuneVelocity::get);
Using a DoubleSupplier means the command picks up live changes from NetworkTables (via TuneValue) or sensor readings without needing to be rescheduled. This is especially useful during tuning on hardware.

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CachedDouble for CANbus efficiency

Any sensor value read over the CAN bus (motor position, velocity, current) should be cached once per periodic loop rather than called multiple times per cycle.
java
// In subsystem periodic() — update once
@Override
public void periodic() {
    cachedPosition.refresh();       // CAN read happens here
    cachedVelocity.refresh();
}

// Elsewhere — read from cache (no CAN traffic)
public double getPositionRotations() {
    return cachedPosition.getValue();
}
The Mechanism base class in SpectrumLib already does this for you — getPosition(), getVelocityRPM(), getVoltage(), and getStatorCurrent() all return CachedDouble values updated in Mechanism.periodic(). You only need to add your own CachedDouble for custom sensors outside the motor controller.

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Method chaining with Triggers and Commands

WPILib’s Trigger and Command APIs are designed for fluent method chaining. Embrace this — it’s more readable than intermediate variables for simple binding.
java
// Command chaining
pilot.RT
    .and(pilot.LT.negate())
    .onTrue(applyState(State.INTAKE_FUEL));

// Composed commands
Command scoringSequence = indexer.feedToLauncher()
    .andThen(launcher.shoot())
    .withTimeout(2.0);

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Java workspace cleanup

If VS Code shows red errors that don’t match actual code problems (common after switching branches or pulling large changes): 
# Option 1: Gradle clean
./gradlew clean

# Option 2: VS Code command palette
# Ctrl+Shift+P → "Java: Clean Java Language Server Workspace"

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Coordinate systems

FRC uses a specific field coordinate system that affects swerve drive, vision, and autonomous path planning:
  • X axis: Positive toward the opposing alliance wall
  • Y axis: Positive to the left when facing the opposing wall
  • Rotation: Counter-clockwise positive (following right-hand rule)
The WPILib pose estimator, PathPlanner, and Limelight all use this convention. Ensure any manual coordinate transformations respect these directions.

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2026 season code goals

Spectrum’s development priorities for 2026, which shape how the codebase is structured:

Sim-first development

Develop and validate all code in WPILib simulation before touching hardware. Robot time is reserved for tuning and final verification.

Trigger-based states

Replace large CommandGroup sequences with Trigger-driven states. Fewer nested command groups means easier debugging and more flexible behavior.

Multi-robot support

One codebase runs on FM, XM, PM, and AM robots via the Rio.id config system. No robot-specific forks.

Improved logging

DogLog and AdvantageScope for structured data capture, replay, and analysis across all test sessions.

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