README.md

off_highway_common

The off_highway_common package provides a C++ library to

• receive can_msgs/Frame ROS messages and decode their bytes into custom C++ message structures,
• encode the bytes of can_msgs/Frame 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_common::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 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 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_common::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

• received_messages (can_msgs/Frame)
  • CAN frames to decode

Published Topics

• /diagnostics (diagnostic_msgs/DiagnosticArray)
  • Update Rate: normally 1 Hz, can be forced
  • Diagnostic error in base class only contains timeout status

Parameters

See receiver_params.yaml.

Sender

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

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_common::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

• sent_messages (can_msgs/Frame)
  • Encoded CAN frames
• /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.