WPILibC (C++) API

WPILibC is the C++ implementation of WPILib, providing high-performance robot control with modern C++20 features.

Namespace Structure

All WPILibC classes are in the frc namespace.

#include <frc/TimedRobot.h>
#include <frc/DriverStation.h>

namespace frc {
  // All WPILib C++ classes
}

Core Robot Classes

TimedRobot

Event-driven robot framework with periodic callbacks

DriverStation

Interface to FMS and driver station data

RobotController

Access to roboRIO system-level functions

RobotBase

Base class for all robot programs

Hardware I/O

Digital I/O

Class	Header	Description
`DigitalInput`	`frc/DigitalInput.h`	Read digital input signals
`DigitalOutput`	`frc/DigitalOutput.h`	Control digital output signals
`Counter`	`frc/Counter.h`	Count digital pulses and edges
`Encoder`	`frc/Encoder.h`	Quadrature encoder support
`DutyCycle`	`frc/DutyCycle.h`	Read PWM duty cycle signals
`DutyCycleEncoder`	`frc/DutyCycleEncoder.h`	Absolute encoders using duty cycle

Analog I/O

Class	Header	Description
`AnalogInput`	`frc/AnalogInput.h`	Read analog voltage inputs (0-5V)
`AnalogOutput`	`frc/AnalogOutput.h`	Generate analog voltage outputs
`AnalogEncoder`	`frc/AnalogEncoder.h`	Analog absolute encoder support
`AnalogPotentiometer`	`frc/AnalogPotentiometer.h`	Potentiometer input with scaling
`AnalogTrigger`	`frc/AnalogTrigger.h`	Trigger actions based on analog thresholds

Motor Controllers

Class	Header	Description
`PWMSparkMax`	`frc/motorcontrol/PWMSparkMax.h`	Control REV Robotics SPARK MAX
`PWMTalonSRX`	`frc/motorcontrol/PWMTalonSRX.h`	Control CTRE Talon SRX
`PWMVictorSPX`	`frc/motorcontrol/PWMVictorSPX.h`	Control CTRE Victor SPX
`Spark`	`frc/motorcontrol/Spark.h`	Generic SPARK controller

Pneumatics

Class	Header	Description
`Compressor`	`frc/Compressor.h`	Control pneumatic compressor
`Solenoid`	`frc/Solenoid.h`	Single solenoid valve control
`DoubleSolenoid`	`frc/DoubleSolenoid.h`	Double solenoid valve control

Sensors

Gyroscopes

ADIS16448_IMU - Analog Devices IMU
ADIS16470_IMU - Analog Devices IMU
ADXRS450_Gyro - Analog Devices SPI gyro
AnalogGyro - Analog gyroscope

Accelerometers

ADXL345_I2C - I2C accelerometer
ADXL345_SPI - SPI accelerometer
ADXL362 - SPI accelerometer
BuiltInAccelerometer - roboRIO accelerometer

TimedRobot

The TimedRobot class provides a framework where methods are called periodically at a fixed rate.

#include <frc/TimedRobot.h>
#include <units/time.h>

namespace frc {

class TimedRobot : public IterativeRobotBase {
 public:
  // Default loop period (20ms = 50Hz)
  static constexpr auto kDefaultPeriod = 20_ms;
  
  // Constructors
  explicit TimedRobot(units::second_t period = kDefaultPeriod);
  explicit TimedRobot(units::hertz_t frequency);
  
  // Add custom periodic callback
  void AddPeriodic(std::function<void()> callback,
                   units::second_t period,
                   units::second_t offset = 0_s);
  
  void StartCompetition() override;
  void EndCompetition() override;
};

}  // namespace frc

Example Usage

#include <frc/TimedRobot.h>
#include <frc/motorcontrol/Spark.h>

class MyRobot : public frc::TimedRobot {
 public:
  void RobotInit() override {
    m_motor.SetInverted(false);
  }
  
  void TeleopPeriodic() override {
    // Called every 20ms during teleop
    m_motor.Set(0.5);
  }
  
  void DisabledInit() override {
    m_motor.Set(0.0);
  }
  
 private:
  frc::Spark m_motor{0};
};

#ifndef RUNNING_FRC_TESTS
int main() {
  return frc::StartRobot<MyRobot>();
}
#endif

DriverStation

Provides access to driver station data and FMS information.

#include <frc/DriverStation.h>

namespace frc {

class DriverStation {
 public:
  // Get singleton instance
  static DriverStation& GetInstance();
  
  // Robot state
  bool IsEnabled() const;
  bool IsDisabled() const;
  bool IsAutonomous() const;
  bool IsTeleop() const;
  bool IsTest() const;
  
  // Alliance and location
  std::optional<Alliance> GetAlliance() const;
  std::optional<int> GetLocation() const;
  
  // Match info
  double GetMatchTime() const;
  MatchType GetMatchType() const;
  int GetMatchNumber() const;
  
  // Joystick input
  double GetStickAxis(int stick, int axis) const;
  bool GetStickButton(int stick, int button) const;
  int GetStickPOV(int stick, int pov) const;
  
  enum class Alliance { kRed, kBlue };
  enum class MatchType { kNone, kPractice, kQualification, kElimination };
};

}  // namespace frc

AddressableLED

Control addressable RGB LED strips.

#include <frc/AddressableLED.h>

namespace frc {

class AddressableLED {
 public:
  explicit AddressableLED(int port);
  
  void SetLength(int length);
  void SetData(const AddressableLEDBuffer& data);
  void Start();
  void Stop();
};

class AddressableLEDBuffer {
 public:
  explicit AddressableLEDBuffer(int length);
  
  void SetRGB(int index, int r, int g, int b);
  void SetHSV(int index, int h, int s, int v);
  void SetLED(int index, const Color& color);
};

}  // namespace frc

Units Library Integration

WPILibC uses the units library for type-safe physical quantities.

#include <units/length.h>
#include <units/velocity.h>
#include <units/acceleration.h>
#include <units/angle.h>
#include <units/angular_velocity.h>
#include <units/time.h>
#include <units/voltage.h>
#include <units/current.h>

// Example usage
units::meter_t distance = 1.5_m;
units::meters_per_second_t velocity = 2.0_mps;
units::degree_t angle = 90.0_deg;
units::radian_t radians = 1.57_rad;

Filesystem

Access robot filesystem paths.

#include <frc/Filesystem.h>

namespace frc::filesystem {

// Get deploy directory path
std::string GetDeployDirectory();

// Get operating directory
std::string GetOperatingDirectory();

// Get launch directory
std::string GetLaunchDirectory();

}  // namespace frc::filesystem

Smart Pointers and RAII

WPILibC uses RAII principles and smart pointers for automatic resource management.

#include <frc/DigitalInput.h>
#include <memory>

class MyRobot : public frc::TimedRobot {
 private:
  // Automatically cleaned up when MyRobot is destroyed
  frc::DigitalInput m_limitSwitch{0};
  
  // Or use smart pointers for dynamic allocation
  std::unique_ptr<frc::DigitalInput> m_sensor;
  
  void RobotInit() override {
    m_sensor = std::make_unique<frc::DigitalInput>(1);
  }
};

Error Handling

WPILibC uses exceptions for error handling.

#include <frc/Errors.h>

try {
  frc::DigitalInput input(99);  // Invalid channel
} catch (const std::exception& e) {
  frc::ReportError(frc::err::Error, "{}", e.what());
}

Data Logging

Class	Header	Description
`DataLogManager`	`frc/DataLogManager.h`	Manage robot data logging
`Alert`	`frc/Alert.h`	Create and manage robot alerts

Utility Classes

Class	Header	Description
`Timer`	`frc/Timer.h`	Timing and delay utilities
`Watchdog`	`frc/Watchdog.h`	Monitor loop timing
`Notifier`	`frc/Notifier.h`	Schedule callbacks
`EventLoop`	`frc/event/EventLoop.h`	Event-driven programming

Source Code

View the full source code on GitHub:

WPILibJ API

Java implementation of WPILib

Command Framework

Command-based programming framework

HAL API

Hardware Abstraction Layer

WPIMath

Mathematics and control libraries

Core Libraries

Math & Utilities

Networking & Vision

Command Framework

Simulation

WPILibC (C++) API

Namespace Structure

Core Robot Classes

TimedRobot

DriverStation

RobotController

RobotBase

Hardware I/O

Digital I/O

Analog I/O

Motor Controllers

Pneumatics

Sensors

Gyroscopes

Accelerometers

TimedRobot

Example Usage

DriverStation

AddressableLED

Units Library Integration

Filesystem

Smart Pointers and RAII

Error Handling

Data Logging

Utility Classes

Source Code

WPILibJ API

Command Framework

HAL API

WPIMath

Build docs developers (and LLMs) love

Core Libraries

Math & Utilities

Networking & Vision

Command Framework

Simulation

​Namespace Structure

​Core Robot Classes

TimedRobot

DriverStation

RobotController

RobotBase

​Hardware I/O

​Digital I/O

​Analog I/O

​Motor Controllers

​Pneumatics

​Sensors

Gyroscopes

Accelerometers

​TimedRobot

​Example Usage

​DriverStation

​AddressableLED

​Units Library Integration

​Filesystem

​Smart Pointers and RAII

​Error Handling

​Data Logging

​Utility Classes

​Source Code

​Related Documentation

WPILibJ API

Command Framework

HAL API

WPIMath

Build docs developers (and LLMs) love

Namespace Structure

Core Robot Classes

Hardware I/O

Digital I/O

Analog I/O

Motor Controllers

Pneumatics

Sensors

TimedRobot

Example Usage

DriverStation

AddressableLED

Units Library Integration

Filesystem

Smart Pointers and RAII

Error Handling

Data Logging

Utility Classes

Source Code

Related Documentation