Commands and triggers

Commands describe actions. Triggers convert operator or robot conditions into scheduling decisions.

Choose binding semantics deliberately

driver.a().whileTrue(intake.acquireCommand());
driver.b().onTrue(intake.stowCommand());
driver.x().toggleOnTrue(drivetrain.precisionModeCommand());

• onTrue schedules once at the rising edge.
• whileTrue keeps the command associated with the held condition.
• toggleOnTrue persists state and therefore needs a clear operator indication.

Prefer command factories

public Command acquireCommand() {
  return startEnd(
      () -> requestGoal(IntakeGoal.ACQUIRE),
      () -> requestGoal(IntakeGoal.IDLE));
}

The subsystem can provide commands that preserve its requirements and cleanup rules. The controls layer decides which input uses them.

Finish conditions must mean something

return run(() -> requestGoal(goal))
    .until(this::atGoal)
    .withTimeout(1.5)
    .finallyDo(interrupted -> recordResult(interrupted, atGoal()));

A timeout prevents an endless command, but it should not silently report success. Record whether the goal was reached.

Defaults

A default command runs when no other command requires the subsystem. Drivetrain teleoperation is a common example. Defaults should tolerate being interrupted and resumed at any time.

Review questions

• Does the command require every subsystem it writes to?
• Can it finish, time out, or be canceled safely?
• Does interruption leave a known goal?
• Can the driver tell whether a toggle is active?
• Is the binding separate from mechanism safety?