CAN Bus

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Overview

The CAN bus is an ISO standard bus originally developed for vehicles. It manages the Chassis Electrical System Control and is responsible for critical activities like engine electrical, and skid control. This system is also used to provide vehicle diagnostic information for maintenance. A multi-star configuration seems typical of this bus with a primary bus line that branches into sub bus lines at its extremities then attaches to multiple device nodes. Differential voltage is applied over twisted pair at 1.5 to 2.5V and 2.5 to 3.5V for noise resistant signaling. Bit rates up to 1 Mbit/s are possible at network lengths below 40 m. Decreasing the bit rate allows longer network distances (e.g., 500 m at 125 kbit/s). (Jeremiah J. Flerchinger Source) Controllers supporting CAN FD, an enhanced CAN version with frames up to 64 byte and bit rates up to 4 Mbit/s, will be available in the second half of 2014. A can4linux version supportig CAN FD on a IFI CAN is ready to be used.

Although developed as car communication network CAN is used in many other areas, industrial, medical, maritime laboratory and more. Most often with a CAN based higher layer protocol like CANopen on top of it.


Additional information can be found at:

http://en.wikipedia.org/wiki/CAN_bus
SocketCAN News
CiA CAN in Automation CAN user association
CAN Wiki
CAN FD Specification Version 1.0

CAN Support in Linux

CAN is supported by Linux device drivers. Mainly two types exist. Character device based drivers and network socket based drivers. The Linux kernel supports CAN with the SocketCAN framework.

One of the character based drivers is can4linux.

SocketCAN Supported Protocols

  • RAW: send & receive raw CAN frames
  • BCM: Broadcast manager, offload repetitive work to the Linux kernel
  • ISOTP ...
  • SAE J1939

SocketCAN Supported Controllers

  • Microchip MCP251x
  • Atmel AT91 SoCs
  • ESD 331 CAN Cards
  • NXP (Philips) SJA1000
  • Freescale MPC52xx SoCs
  • Bosch CC770
  • Intel AN82527
  • TIs SoCs
  • Serial/network devices utilizing ASCII protocol (slcan driver)
Vendor Device Name Driver Module Name Controller Kconfig Option Linux Mainline Remarks
VScom NET-CAN slcan (unknown) CONFIG_CAN_SLCAN 2.6.38 needs slcand and socat
VScom PCI-2CAN slcan (unknown) CONFIG_CAN_SLCAN 2.6.38 needs slcand
VScom SER-CAN slcan (unknown) CONFIG_CAN_SLCAN 2.6.38 needs slcand
VScom USB-CAN slcan (unknown) CONFIG_CAN_SLCAN 2.6.38 needs slcand
LAWICEL CAN232 slcan (unknown) CONFIG_CAN_SLCAN 2.6.38 needs slcand
LAWICEL CANUSB slcan (unknown) CONFIG_CAN_SLCAN 2.6.38 needs slcand
PEAK PCAN-PCI peak_pci sja1000 CONFIG_CAN_PEAK_PCI 3.2 supports all PCAN-[mini]PCI[e][104] variants
PEAK PCAN-USB peak_usb (unknown) CONFIG_CAN_PEAK_USB 3.4 supports PCAN-USB[pro][hub] (no LIN support)
Kvaser PCIcanx kvaser_pci sja1000 CONFIG_CAN_KVASER_PCI 2.6.31 supports all PCI-[mini]PCI[e][104] variants
Kvaser Leaf kvaser_usb (unknown) CONFIG_CAN_KVASER_USB 3.8 supports USB Leaf / Memorator / Blackbird / R (see detailed USB device IDs in kvaser_usb.c)
EMS Wünsche CPC-Card ems_pcmcia sja1000 CONFIG_CAN_EMS_PCMCIA 3.2 discontinued
EMS Wünsche CPC-USB/ARM7 ems_usb (unknown) CONFIG_CAN_EMS_USB 3.2
EMS Wünsche CPC-PCI/PCIe ems_pci sja1000 CONFIG_CAN_EMS_PCI 3.2 up to four channel
EMS Wünsche CPC-PC104P ems_pci sja1000 CONFIG_CAN_EMS_PCI 3.2 up to four channel on a PC104+ board
8devices USB2CAN usb_8dev (STR750FV2) CONFIG_CAN_8DEV_USB 3.9 STR750FV2 Firmware
Softing CANcard2 softing_cs sja1000 or NEC-005(?) CONFIG_CAN_SOFTING_CS 2.6.38 Supports {CAN,EDIC}card{,SJA,2} PCMCIA cards

Needs firmware softing-fw-4.6-binaries.tar.gz

SocketCAN Support in Programming Languages/Environments

can4linux Supported Controllers

  • Allwinner A20 with integrated CAN (on the popular BananaPi single-board computer.)
  • Analog Devices BlackFin BF537
  • Atmel AT91 SoCs
  • Freescale FlexCAN (ColdFire 5282, i.MX25, i.MX28, i.MX35)
  • Intel 82527 (the replacement Bosch CC770 should work)
  • Microchip Stand Alone CAN MCP2515
  • NXP Stand Alone CAN SJA1000 (on different ISA or PCI/PCIe boards)
  • Xilinx Zynq with XCAN
  • 'virtual' CAN mode without CAN hardware
  • 'virtual' CAN mode supporting CAN FD
  • IFI CAN FPGA IP, in classic CAN mode and CAN FD mode

can4linux Support in Programming Languages/Environments

  • C - many examples and useful applications are provided with the package, check can4linux-examples/
  • Tcl/Tk also in can4linux-examples/
  • Python also in can4linux-examples/

CAN Controllers Emulation (WIP/experimental)

  • SJA1000 CAN controller based PCI board emulation for QEMU
    • Cards models provided:
      • Simple memory mapped SJA1000 in the first PCI BAR with ad-hoc PCI ID
      • Kvaser PCIcan-S single I/O mapped SJA1000 model compatible with kvaser_pci Linux driver on guest side
    • The emulated CAN buses can be connected to virtual or physical SocketCAN interface if Linux is used as host system
    • Project repository: https://github.com/CTU-IIG/qemu
    • Work started by 2013 GSoC project when RTEMS project donated its slot to work on QEMU CAN support - see RTEMS related page for more info and use instructions

SocketCAN Bechmarking

SocketCAN Tutorials