On some Clearpath robot platforms, a CAN bus is used to communicate and control motors, battery systems, safety rated controllers, e-stop receivers, and more. Using the Clearpath configuration file, it is possible to define of a CAN-to-UDP, CAN-to-Serial, or CAN-to-USB adapter. At run time, these adapters are brought up and configured with the defined parameters.

Baud Rates

In the parameters, the baud rates should be set as speeds in slcand:

Speed	Baud Rate
s0	10 Kbit/s
s1	20 Kbit/s
s2	50 Kbit/s
s3	100 Kbit/s
s4	125 Kbit/s
s5	250 Kbit/s
s6	500 Kbit/s
s7	800 Kbit/s
s8	1000 Kbit/s

Virtual CAN Adapters

By default, the A300 Husky, DD100-D0150 Dingo series, and R100 Ridgeback use CAN to communicate with the motor drivers. However, the physical CAN bus is connected to the MCU and bridged over UDP to the robot computer.

To establish this bridge from the computer side, a socat command needs to be issued to create a virtual serial device. Using the virtual serial device, the slcand command is used to create a virtual CAN device. Then, the virtual CAN device can be configured using ip link and brought up.

If every robot platform had the same CAN bus requirements, this process could be automated by a simple bash script. However, the baud-rate, ports, and number of CAN buses may vary between platform. For example, a second bus is required on the A300 Husky to establish communication with the batteries.

Fields required for a virtual CAN adapter:

• type: Must be set to virutal
• can_dev: The name of the CAN interface to be created.
• port: The port number of the socket on the MCU.
• serial_dev: The serial device that will be created to bridge the UDP serial data.
• baud: The baud rate of the CAN interface. See above for list.

Below are the default configurations for each robot platform. If the can_adapters entry is left empty, these are configurations that will be applied. If a can_adapter entry with the same can_dev, CAN device name, is passed in as one of the defaults, it will override them.

A300

The default A300 Husky CAN adapter configuration requires two CAN buses bridged over UDP. Therefore, these are both set to type virtual.

For example, the first, vcan0, is set to bridge a UDP serial using port 11412 and create a virtual serial device /dev/ttycan0. Then, it will create a virtual CAN device using with baud rate s8, 1 megabaud and will be named vcan0.

platform:
  can_adapters:
    - can_dev: vcan0
      type: virtual
      port: 11412
      serial_dev: /dev/ttycan0
      baud: s8
    - can_dev: vcan1
      type: virtual
      port: 11413
      serial_dev: /dev/ttycan1
      baud: s5

DD100-DO150

The default DD100-DO150 Dingo CAN adapter configuration requires one CAN bus bridged over UDP.

platform:
  can_adapters:
    - can_dev: vcan0
      type: virtual
      port: 11412
      serial_dev: /dev/ttycan0
      baud: s8

R100

The default R100 Dingo CAN adapter configuration requires one CAN bus bridged over UDP.

platform:
  can_adapters:
    - can_dev: vcan0
      type: virtual
      port: 11412
      serial_dev: /dev/ttycan0
      baud: s8

Serial CAN Adapters

In the event that it is required to integrate a CAN device on the robot, it is possible to use a USB CAN-to-Serial adapter. These adapters are easy to acquire and trivial to setup. However, these devices still require the slcand command to create the virtual CAN device with the appropriate baud rate. The virtual CAN device will also need to be configured using ip link and brought up.

Fields required for a serial CAN adapter:

• type: Must be set to serial
• can_dev: The name of the CAN interface to be created.
• serial_dev: The path to the serial device.
• baud: The baud rate of the CAN interface. See above for list.

To define a serial CAN adapter in the robot configuration YAML, use type serial, define the serial_dev that the device is registered as, define the baud rate, and the name of the virtual can_dev to create.

platform:
  can_adapters:
    - can_dev: usbcan0
      type: serial
      serial_dev: /dev/ttyUSB0
      baud: s8

Physical USB CAN Adapters

Just as the serial CAN adapters, USB physical CAN adapters are trivial to setup, but are generally harder to obtain. Out of the three options, these adapters are the easiest to setup as they only need the ip link command to bring up.

Fields required for a physical CAN adapter:

• type: Must be set to physical
• can_dev: The name of the physical interface.
• baud: The baud rate of the CAN interface. See above for list.

To define a physical USB CAN adapter in the robot configuration YAML, use the type physical that the physical CAN is registered as and the baud rate.

platform:
  can_adapters:
    - can_dev: can0
      type: physical
      baud: s8