API Reference

This section contains the complete API documentation for all LittleBot packages.

C++ API

Hardware Interface

namespace littlebot_base

To more information about the serial library used, please visit: https://github.com/NestorDP/cppserial.

Enums

enum class SerialError

Values:

enumerator None
enumerator PortUnavailable
enumerator InsufficientPermissions
enumerator ConfigBaudrateFailed
enumerator ReadFailed
enumerator WriteFailed
enumerator AlreadyOpen
enumerator NotOpen
enumerator NotClosed
enumerator Unknown
enum class DriverError

Values:

enumerator None
enumerator NoData
enumerator DecodeFailure
enumerator EncodeFailure
enumerator SizeMismatch
enumerator SerialReadError
enumerator SerialWriteError
enumerator InvalidControlChar
enumerator NoCommand
enumerator SerialPortUnavailable
enumerator SerialInsufficientPermissions
enumerator SerialConfigBaudrateFailed
enumerator SerialReadFailed
enumerator SerialWriteFailed
enumerator SerialAlreadyOpen
enumerator SerialNotOpen
enumerator SerialNotClosed
enumerator Unknown

Variables

constexpr size_t kNumWheels = 2
class ILittlebotDriver
#include <i_littlebot_driver.hpp>

Subclassed by littlebot_base::LittlebotDriver

Public Functions

ILittlebotDriver(const ILittlebotDriver&) = delete

Prevent copy and assignment.

virtual ~ILittlebotDriver() = default

Deconstructor for the ILittlebotDriver class.

virtual DriverError init() noexcept = 0

Initialize the driver.

Returns:

DriverError The result of the initialization

virtual void readRTData(WheelRTData &state) const noexcept = 0

Read the current state from the RT buffer.

Note

This method is RT-safe (control loop)

Parameters:

state – Reference to WheelRTData structure to store the read data

virtual void writeRTData(const WheelRTData &command) noexcept = 0

Write the command to the RT buffer.

Note

This method is RT-safe (control loop)

Parameters:

command – Reference to WheelRTData structure containing the command data

virtual bool requestStatus() noexcept = 0

Receive data from the hardware and update the RT buffer.

Note

This method is NOT RT-safe (executor / IO thread)

Returns:

true if data was received successfully

Returns:

false if an error occurred

virtual bool sendCommand() noexcept = 0

Send command data to the hardware.

Note

This method is NOT RT-safe (executor / IO thread)

Returns:

true if data was sent successfully

Returns:

false if an error occurred

virtual DriverError getLastError() const noexcept = 0

Get the last error that occurred.

Returns:

DriverError The last error code

virtual const DriverErrorCounters &getErrorCounters() const noexcept = 0

Get the error counters.

Returns:

const DriverErrorCounters& Reference to the error counters structure

Public Static Attributes

static constexpr char kCommandChar = {'C'}

Command control characters.

static constexpr char kStatusChar = {'S'}

Status control characters.

class ILittlebotDriverFactory
#include <i_littlebot_driver_factory.hpp>

Subclassed by littlebot_base::LittlebotDriverFactory

template<typename T>
class IRTBuffer
#include <i_rt_buffer.hpp>
class ISerialPort
#include <i_serial_port.hpp>

Subclassed by littlebot_base::SerialPort

Public Functions

virtual ~ISerialPort() = default

Deconstructor for the ISerialPort class.

virtual SerialError open(std::string port, int baudrate) noexcept = 0

Open the serial port.

Parameters:

  • port – Serial port device path (e.g., “/dev/ttyUSB0”)

  • baudrate – Baud rate for the serial communication

Returns:

SerialError indicating success or type of failure

virtual SerialError close() noexcept = 0

Close the serial port.

Returns:

SerialError indicating success or type of failure

virtual int read(std::vector<uint8_t> &payload) noexcept = 0

Read Packet from the serial port.

Parameters:

payload – Vector to store the read packet data. Implementations must ensure the frame size never exceeds kMaxFrameSize.

Returns:

Number of bytes read

virtual int write(const std::vector<uint8_t> &payload) noexcept = 0

Write Packet to the serial port.

Parameters:

payload – Vector containing the packet data to write payload.size() must be <= kMaxFrameSize.

Returns:

Number of bytes written

inline virtual bool isOpen() const noexcept

Check if the serial port is open.

Returns:

true if the serial port is open

Returns:

false if the serial port is closed

Public Static Attributes

static constexpr size_t kMaxFrameSize = 256

Maximum size of a frame that can be sent/received.

class LittlebotDriver : public littlebot_base::ILittlebotDriver
#include <littlebot_driver.hpp>

Public Functions

LittlebotDriver(std::shared_ptr<ISerialPort> serial_port, std::shared_ptr<IRTBuffer<WheelRTData>> rt_state_buffer, std::shared_ptr<IRTBuffer<WheelRTData>> rt_command_buffer, const std::vector<std::string> &joint_names, std::string port, int baudrate)

Construct a new Littlebot Driver object.

Parameters:

  • serial_port – Shared pointer to the serial port interface

  • rt_state_buffer – Shared pointer to the real-time buffer interface for wheel state data

  • rt_command_buffer – Shared pointer to the real-time buffer interface for wheel command data

  • joint_names – Vector of joint names

  • port – Serial port name

  • baudrate – Serial port baudrate

virtual DriverError init() noexcept override

Initialize the driver.

Override the virtual method from ILittlebotDriver

virtual void readRTData(WheelRTData &state) const noexcept override

Read the current state from the RT buffer.

Override the virtual method from ILittlebotDriver

virtual void writeRTData(const WheelRTData &command) noexcept override

Write the command to the RT buffer.

Override the virtual method from ILittlebotDriver

virtual bool requestStatus() noexcept override

Receive data from the hardware and update the RT buffer.

Override the virtual method from ILittlebotDriver

virtual bool sendCommand() noexcept override

Send command data to the hardware.

Override the virtual method from ILittlebotDriver

inline virtual DriverError getLastError() const noexcept override

Get the last error that occurred.

Override the virtual method from ILittlebotDriver

inline virtual const DriverErrorCounters &getErrorCounters() const noexcept override

Get the error counters.

Override the virtual method from ILittlebotDriver

class LittlebotDriverFactory : public littlebot_base::ILittlebotDriverFactory
#include <littlebot_driver_factory.hpp>
class LittlebotHardwareComponent : public hardware_interface::SystemInterface
#include <littlebot_hardware_component.hpp>

Public Functions

LittlebotHardwareComponent() = default

Default constructor for the LittlebotHardwareComponent class.

~LittlebotHardwareComponent() = default

Deconstructor for the LittlebotHardwareComponent class.

hardware_interface::CallbackReturn on_init(const hardware_interface::HardwareComponentInterfaceParams &params) override

Initialize the hardware component with the given parameters.

hardware_interface::CallbackReturn on_configure(const rclcpp_lifecycle::State &state) override

Configure the hardware communication.

std::vector<hardware_interface::StateInterface> export_state_interfaces() override

Export the state interfaces.

std::vector<hardware_interface::CommandInterface> export_command_interfaces() override

Export the command interfaces.

hardware_interface::return_type read(const rclcpp::Time &time, const rclcpp::Duration &period) override

Read the state of the hardware component.

hardware_interface::return_type write(const rclcpp::Time &time, const rclcpp::Duration &period) override

Write the command to the hardware component.

inline void setDriverFactory(std::shared_ptr<ILittlebotDriverFactory> factory)

Set the Littlebot driver factory.

Note

This method is mainly used for testing purposes

Parameters:

factory – Shared pointer to the Littlebot driver factory

class RosRTBuffer : public littlebot_base::IRTBuffer<littlebot_base::WheelRTData>
#include <ros_rt_buffer.hpp>
class SerialPort : public littlebot_base::ISerialPort
#include <serial_port.hpp>

Public Functions

virtual SerialError open(std::string port, int baudrate) noexcept override

Open the serial port.

Override the virtual method from ISerialPort

virtual SerialError close() noexcept override

Close the serial port.

Override the virtual method from ISerialPort

virtual int read(std::vector<uint8_t> &payload) noexcept override

Read packet data from the serial port.

Override the virtual method from ISerialPort

virtual int write(const std::vector<uint8_t> &payload) noexcept override

Write packet data to the serial port.

Override the virtual method from ISerialPort

struct WheelRTData
#include <types.hpp>
struct DriverErrorCounters
#include <types.hpp>
class Wheel
#include <wheel.hpp>

Public Functions

inline void setCommandVelocity(double velocity)

Set the command velocity for the wheel.

Parameters:

velocity – Desired command velocity

inline void setJointName(const std::string &joint_name)

Set the joint name for the wheel.

Parameters:

joint_name – Name of the joint

inline void setStatusVelocity(double velocity)

Set the status velocity for the wheel.

Parameters:

velocity – Measured status velocity

inline void setStatusPosition(double position)

Set the status position for the wheel.

Parameters:

position – Measured status position

inline double getCommandVelocity() const

Get the command velocity for the wheel.

inline double getStatusPosition() const

Get the status position for the wheel.

inline double getStatusVelocity() const

Get the status velocity for the wheel.

inline std::string getJointName() const

Get the joint name for the wheel.

namespace codec

Functions

void encode(std::vector<uint8_t> &payload, const std::vector<Wheel> &wheels)

Encode wheel command data into a protobuf payload.

This function serializes the command velocities of the wheels into a protobuf message suitable for transmission to the hardware.

Parameters:

  • payload – Output payload that will contain the serialized protobuf message

  • wheels – Vector of wheels providing command data

Throws:

std::runtime_error – if serialization fails

void decode(const std::vector<uint8_t> &payload, std::vector<Wheel> &wheels)

Decode wheel state data from a protobuf payload.

This function deserializes a protobuf message received from the hardware and updates the wheel status fields. Existing wheel metadata (e.g., joint names) is preserved.

Parameters:

  • payload – Input payload containing the serialized protobuf message

  • wheels – Vector of wheels to be updated with decoded state data

Throws:

std::runtime_error – if parsing fails or data size mismatches

Communication

Warning

doxygenclass: Cannot find class “littlebot_base::LittlebotCommunication” in doxygen xml output for project “littlebot” from directory: /home/docs/checkouts/readthedocs.org/user_builds/littlebot/checkouts/latest/docs/doxygen/xml

RQT Plugin

Warning

doxygennamespace: Cannot find namespace “littlebot_rqt_plugin” in doxygen xml output for project “littlebot” from directory: /home/docs/checkouts/readthedocs.org/user_builds/littlebot/checkouts/latest/docs/doxygen/xml

Python API

Scripts and Tools

Launch Files