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CAN

Interface for CAN based devices. This also includes interfaces for CANopen.

This repository contains the following packages:

  • arti_can_interface contains the library to access the CAN more easily. The package also contains a node for CAN bus introspection.
  • arti_can_msgs contains messages sent by the nodes to allow introspection of the CAN bus or sending messages to the CAN bus.

Installation of the lely CANopen library

Installation instructions are taken from https://opensource.lely.com/canopen/docs/installation/. The installation is performed from sources, as Ubuntu 16.04 does not provide the proper library packages:

sudo apt-get install \
    git build-essential automake libtool \
    libbluetooth-dev \
    valgrind \
    doxygen graphviz can-utils

cd ~/Downloads/
git clone -b v2.2.1 https://gitlab.com/lely_industries/lely-core.git
cd lely-core

autoreconf -i
mkdir build
cd build
../configure --disable-python

make -j8 -l8
make check
sudo make install

Setting up a CAN interface

sudo ip link set can0 type can bitrate 500000
sudo ip link set can0 txqueuelen 1024
sudo ip link set up can0

Note: if the TX queue length is too small, opening the CAN interface with lely may result in an "operation not permitted" error.

Setting up a virtual CAN interface

To test a CAN connection one can create a virtual CAN device:

sudo modprobe vcan

sudo ip link add dev vcan0 type vcan
sudo ip link set up vcan0

ip link show vcan0

The show command should show something similar to:

3: vcan0: <NOARP,UP,LOWER_UP> mtu 72 qdisc noqueue state UNKNOWN mode DEFAULT group default qlen 1000
    link/can

There is also a script for this purpose:

rosrun arti_can_interface setup_vcan.sh vcan0

To delete a virtual CAN device, run:

sudo ip link set down vcan0
sudo ip link delete dev vcan0

or

rosrun arti_can_interface delete_vcan.sh vcan0

Testing CAN interfaces

The output of a CAN message can be shown by dumping the device as follows:

candump vcan0

A CAN message can be sent using the following command, giving the CAN device, ID, and data bytes:

cansend vcan0 18c#017f

To setup two CAN devices talking to each other use the following:

sudo modprobe can-gw

sudo cangw -A -s vcan0 -d vcan1 -e
sudo cangw -A -s vcan1 -d vcan0 -e

To create two virtual CAN devices talking to each other use:

rosrun arti_can_interface setup_connected_vcans.sh vcan0 vcan1

The CAN interface node can also be used with a dump file and a command file:

roslaunch arti_can_interface can_interface.launch device_name:=vcan0 dump_file_name:=dump.txt command_file_name:=commands.txt command_interval:=2.0

A command file looks like this:

# Transmit CAN messages:
tx;0x185;1;2;3
tx;0;

# Fake reception of CAN messages:
rx;0x205;10;0x10;010

A dump file lists received and transmitted CAN messages in the same format.

Sending CAN messages

The example below shows how to send a message with the CAN interface. There are several methods to send a message; the one shown is the simplest one. See the documentation in can_interface.h for further methods to send CAN messages.

// Create the CAN interface for a specific device:
std::string device_name = "vcan0";
arti_can_interface::CanInterfacePtr can_interface = CanInterface::createCanInterface(device_name);

// Prepare the message data:
std::vector<uint8_t> data;
data.push_back(1);
data.push_back(2);
data.push_back(3);

// Use the specified id for the CAN message:
uint32_t id = 0x185;

// Send the message:
can_interface->sendMessage(id, data);

As an alternative one can also use the helper class CanDataWriter:

// Create the CAN interface for a specific device:
std::string device_name = "vcan0";
arti_can_interface::CanInterfacePtr can_interface = CanInterface::createCanInterface(device_name);

// Prepare the message data:
arti_can_interface::CanDataWriter::Buffer data;
arti_can_interface::CanDataWriter writer{data};
writer.writeUnsignedInt8(1);
writer.writeUnsignedInt8(2);
writer.writeUnsignedInt8(3);

// Write more complicated data types
writer.writeUnsignedInt16(1234);
writer.writeFloatAsInt16(5678.9);

// Use the specified id for the CAN message:
uint32_t id = 0x185;

// Send the message:
can_interface->sendMessage(id, data);

Receiving CAN messages

The example below shows how to register a callback for receiving messages with a specific id. The callback function will be called by the receiving thread, and will block other callback functions. Receiving data can be considered thread-save.

// Create the CAN interface for a specific device:
std::string device_name = "vcan0";
arti_can_interface::CanInterfacePtr can_interface = CanInterface::createCanInterface(device_name);

// The CAN id we're interested in:
uint32_t id = 0x185;

// Subscribe to messages with the given id:
can_interface->subscribe(id, &canMessageCB);

...

// An example callback:
void canMessageCB(const arti_can_msgs::CanMessageConstPtr& can_message)
{
  ROS_INFO_STREAM("id: " << can_message->id);
  ROS_INFO_STREAM("extended_id: " << static_cast<int>(can_message->extended_id));
  ROS_INFO_STREAM("rtr: " << static_cast<int>(can_message->rtr));
  ROS_INFO_STREAM("extended_data_length: " << static_cast<int>(can_message->extended_data_length));
  ROS_INFO_STREAM("bit_rate_switch: " << static_cast<int>(can_message->bit_rate_switch));
  ROS_INFO_STREAM("error_state_indicator: " << static_cast<int>(can_message->error_state_indicator));

  for (const uint8_t data : can_message->data)
  {
    ROS_INFO_STREAM("new byte received: " << static_cast<int>(data));
  }
}

As an alternative one can also use the helper class CanDataReader:

// Create the CAN interface for a specific device:
std::string device_name = "vcan0";
arti_can_interface::CanInterfacePtr can_interface = CanInterface::createCanInterface(device_name);

// The CAN id we're interested in:
uint32_t id = 0x185;

// Subscribe to messages with the given id:
can_interface->subscribe(id, &canMessageCB);

...

// An example callback:
void canMessageCB(const arti_can_msgs::CanMessageConstPtr& can_message)
{
  ROS_INFO_STREAM("id: " << can_message->id);
  ROS_INFO_STREAM("extended_id: " << static_cast<int>(can_message->extended_id));
  ROS_INFO_STREAM("rtr: " << static_cast<int>(can_message->rtr));
  ROS_INFO_STREAM("extended_data_length: " << static_cast<int>(can_message->extended_data_length));
  ROS_INFO_STREAM("bit_rate_switch: " << static_cast<int>(can_message->bit_rate_switch));
  ROS_INFO_STREAM("error_state_indicator: " << static_cast<int>(can_message->error_state_indicator));

  for (const uint8_t data : can_message->data)
  {
    ROS_INFO_STREAM("new byte received: " << static_cast<int>(data));
  }

  arti_can_interface::CanDataReader payload_reader(can_message->data.begin(), can_message->data.end());

  auto first_byte = payload_reader.readUnsignedInt8();
  auto second_byte = payload_reader.readUnsignedInt8();
  auto third_byte = payload_reader.readUnsignedInt8();

  // Read more complicated data types
  auto fourth_and_fifth_byte = payload_reader.readUnsignedInt16();
  auto sixth_and_seventh_byte = payload_reader.readInt16AsFloat();
}

License

All files in this repository are distributed under the terms of the 2-clause BSD license. See LICENSE.txt for details.