CAN bus Linux driver

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The current CAN bus driver uses SocketCAN API which is now the official CAN API for Linux. SocketCAN is based on the Linux socket. Further details can be found on the links at the bottom of this page.

Warning Warning: Please ensure that you use a recent version of armadeus BSP (kernel version more than 2.6.38 is required) before trying the instructions described on this page! With older kernel versions you may not be able to change the bitrate.


Driver installation

 $ make linux-menuconfig

Networking support  --->
    <M>   CAN bus subsystem support ---> 
        --- CAN bus subsystem support
        <M>   Raw CAN Protocol (raw access with CAN-ID filtering)
        <M>   Broadcast Manager CAN Protocol (with content filtering)
              CAN Device Drivers  --->
                  <M> Virtual Local CAN Interface (vcan)
                  <M> Platform CAN drivers with Netlink support
                  [*]   CAN bit-timing calculation   
                  <M> Microchip 251x series SPI CAN Controller

 $ make linux
 $ make
  • Reflash kernel and rootfs

Usage

  • Load all the required drivers (not needed on OPOS6UL):
# modprobe can
# modprobe can-dev
# modprobe can-raw
APF27 & APF51 APF6 
# modprobe mcp251x          

# modprobe flexcan
  • Set the bitrate before all operations

Example: Set the bitrate of the can0 interface to 125kbps: 

# ip link set can0 up type can bitrate 125000
Note Note: An error occurs when you try to set the bitrate with an old Linux kernel. In that case, echo 125000 > /sys/devices/platform/FlexCAN.0/bitrate was reported to be a good alternative.


  • If the following error occurs when you do the last instruction :
ip: either "dev" is duplicate, or "type" is garbage

check that this command: 

# which ip

return this message: 

/sbin/ip

and not this one : 

/bin/ip

If the binary is installed in /bin instead of /sbin, the executable file is a link to busybox and the command to set the bitrate doesn't work on busybox, so try the following instructions: 

$ make busybox-clean
$ make busybox-dirclean
$ make menuconfig

Package Selection for the target  --->
    Networking applications  --->
        [*] iproute2

$ make

Then, reflash your rootfs.

Quick test

  • Once the driver is installed and the bitrate is set, the CAN interface has to be started like a standard net interface:
 # ifconfig can0 up
  • and can be stopped like that:
 # ifconfig can0 down
  • The socketCAN version can be retrieved this way:
 # cat /proc/net/can/version
  • The socketCAN statistics can be retrieved this way:
 # cat /proc/net/can/stats

Userspace tools

Several tools are provided by socketCAN:

  • candump: dump traffic on a CAN network

The following command shows the received message from the CAN bus 

candump can0
  • cansend: simple command line tool to send CAN-frames via CAN_RAW sockets

exemple : The following command sends 3 bytes on the bus (0x1E, 0x10, 0x10) with the identifier 500. 

cansend can0 500#1E.10.10

You can send a remote request message 

cansend can0 500#R

The information with the identifier 500 will be available on the bus when the device receive the remote request message

  • cangen: CAN frames generator for testing purpose
  • canplayer: send CAN frames from a file to a CAN interface

These tools can be compiled and installed on the target by means of the Buildroot menuconfig: 

$ make menuconfig

Package Selection for the target  --->
    Networking  --->
        [*]   Socket CAN

$ make

then, reflash your rootfs.

Automatically launch CAN interface at startup

  • Add the following lines to /etc/network/interfaces configuration file:
auto can0
iface can0 inet manual
        pre-up /sbin/ip link set $IFACE type can bitrate 125000 on
        up /sbin/ifconfig $IFACE up
        down /sbin/ifconfig $IFACE down

Links

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