off_highway_can

The off_highway_can package

README

off_highway_can

The off_highway_can package provides a C++ library to

  • receive can_msgs/Frame or socketcan_msgs/FdFrame ROS messages and decode their bytes into custom C++ message structures,

  • encode the bytes of can_msgs/Frame or socketcan_msgs/FdFrame ROS messages from custom C++ message structures and send them.

The list of message structures containing the definition of a CAN message and signals need to be filled by derived classes for CAN node specific functionality. The more generic handling of a cyclic redundancy check and a rolling message counter per message is provided by the library. Have a look directly into the CAN message structure definition for further information.

Classes

Receiver

The off_highway_can::Receiver is an abstract base class and needs to be derived for specific sensor types and behavior. It provides the functionality to process can_msgs/Frame or socketcan_msgs/FdFrame ROS messages and decode configured ones based on provided message definitions. The decoded signal values are forwarded to the derived class for user-defined processing of them.

The off_highway_can::Receiver allows to switch between normal and FD CAN frames via the constructor argument use_fd.

The processing chain is based completely on message callbacks and thus event-based. The needed processing time per message can be logged as ROS debug message at runtime with the compile time optionCOMPILE_DEBUG_LOG.

Furthermore, the off_highway_can::Receiver provides a watchdog which checks whether any configured message was received in the period of time defined by the parameter timeout and sends a diagnostic error on the /diagnostics topic when a timeout occurs.

Subscribed Topics

  • from_can_bus (can_msgs/Frame)

    • CAN frames to decode

    • Disabled by use_fd constructor argument

  • from_can_bus_fd (socketcan_msgs/FdFrame)

    • CAN FD frames to decode

    • Enabled by use_fd constructor argument

Published Topics
Parameters

See receiver_params.yaml.

Sender

The off_highway_can::Sender is an abstract base class and needs to be derived for specific behavior. It provides the functionality to send can_msgs/Frame or socketcan_msgs/FdFrame ROS messages by encoding configured CAN messages as bytes based on provided message definitions. The encoded signal values are published to the to_can_bus or to_can_bus_fd topic.

The off_highway_can::Sender allows to switch between normal and FD CAN frames via the constructor argument use_fd.

The encoding and publishing chain is just a method call and thus event-based. The needed processing time to encode and publish all configured messages can be logged as ROS debug message at runtime with the compile time optionCOMPILE_DEBUG_LOG.

Furthermore, the off_highway_can::Sender provides a watchdog which checks whether a ROS message was published in a defined by the parameter timeout and sends a diagnostic error on the /diagnostics topic when a timeout occurs.

Published Topics

  • to_can_bus (can_msgs/Frame)

    • Encoded CAN frames

    • Disabled by use_fd constructor argument

  • to_can_bus_fd (socketcan_msgs/FdFrame)

    • CAN FD frames to decode

    • Enabled by use_fd constructor argument

  • /diagnostics (diagnostic_msgs/DiagnosticArray)

    • Update Rate: normally 1 Hz, can be forced

    • Diagnostic status in base class only contains timeout status

Parameters

See sender_params.yaml.

Free and Open Source Software (FOSS)

This library uses the libcan-encode-decode library for encoding and decoding raw bytes into / from floating values. See the FOSS documentation for further information.