J1939

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SAE J1939 in Linux

overview

See also on Wikipedia.

SAE J1939 defines a higher layer protocol on CAN. It implements a more sophisticated addressing scheme and extends the maximum packet size above 8 bytes. Several derived specifications exists, which differ from the original j1939 on the application level, like MilCAN, NMEA2000 and especially ISO-11783 (ISOBUS). This last one specifies the so-called ETP (Extended Transport Protocol) which is has been included in this implementation. This inclusion results in a maximum packet size of ((2^24)-1)*7 bytes

Specifications

  • SAE J1939-21 : data link layer
  • SAE J1939-81 : network management
  • ISO 11783-6  : Virtual Terminal (Extended Transport Protocol)

Sources

Support for SAE J1939 in Linux consists of 3 parts:

You probably want all 3 components to get a J1939 linux node working.

The final goal is to have these source trees mainlined.

(The j1939 CAN modules are depreciated)

Build

Build the kernel (necessary)

   $ git clone <yourfavoritelinuxkernel> linux
   $ cd linux
   $ git remote add j1939 git://gitorious.org/~kurt-vd/linux-can/linux-can-j1939.git
   $ git remote update j1939
   $ git merge j1939/j1939-vX.X
   $ make etc.

With j1939-vX.X the branch that matches the closest, but not higher, with your linux version.

Build can-j1939-utils (recommended)

   $ git clone git://gitorious.org/~kurt-vd/linux-can/can-j1939-utils.git
   $ cd can-j1939-utils
   $ make etc.

Or you may merge the j1939 changes into any other can-utils version. This should be fairly simple.

If the branch of linux-can-j1939 that you merged into your kernel was for version 3.7 or higher, use the j1939-v6 branch of can-j1939-utils.

Build iproute2-j1939 (recommended)

   $ git clone git://gitorious.org/~kurt-vd/linux-can/iproute2-j1939.git
   $ cd iproute2
   $ git checkout j1939-vX.X
   $ make etc.

With j1939-vX.X the branch that matches the closest, but not higher, with your linux version.

Or you may merge the j1939 changes into any other iproute2 version. This may be a little more complicated.

Getting Started with J1939

First get a can0 bus on your system.

   $ modprobe vcan
   $ ip link add can0 type vcan
   $ ip link set can0 up

Now start j1939.

   $ modprobe can-j1939
   $ ip link set can0 j1939 on

Now you should be able to use can0 as a j1939 CAN device.