j1939 0.1.0.dev1

Overview

An SAE J1939 CAN Network consists of multiple Electronic Control Units (ECUs). Each ECU can have one or more Controller Applications (CAs). Each CA has its own (unique) Address on the bus. This address is either acquired within the address claiming procedure or set to a fixed value. In the latter case, the CA has to announce its address to the bus to check whether it is free.

The CAN messages in a SAE J1939 network are called Protocol Data Units (PDUs). This definition is not completely correct, but close enough to think of PDUs as the CAN messages.

Features

• one ElectronicControlUnit (ECU) can hold multiple ControllerApplications (CA)

• ECU (CA) Naming according SAE J1939/81

• (under construction) full featured address claiming procedure according SAE J1939/81

• full support of transport protocol according SAE J1939/21 for sending and receiveing

  • Message Packaging and Reassembly (up to 1785 bytes)

    • Transfer Protocol Transfer Data (TP.TD)

    • Transfer Protocol Communication Management (TP.CM)

  • Multi-Packet Broadcasts

    • Broadcast Announce Message (TP.BAM)

• (under construction) Requests (global and specific)

• (under construction) correct timeout and deadline handling

• (under construction) almost complete testcoverage

Installation

As soon the package is available in your distro, it’s as easy as:

$ pip install j1939

In the meanwhile you can either download the wheel-package and issue the command:

$ pip install j1939-0.1.0.dev1-py2.py3-none-any.whl

or do the trick with:

$ git clone https://github.com/benkfra/j1939.git
$ cd j1939
$ pip install .

If you want to be able to change the code while using it, clone it then install it in develop mode:

$ git clone https://github.com/benkfra/j1939.git
$ cd j1939
$ pip install -e .

Quick start

To simply receive all passing (public) messages on the bus you can subscribe to the ECU object.

import logging
import time
import can
import j1939

logging.getLogger('j1939').setLevel(logging.DEBUG)
logging.getLogger('can').setLevel(logging.DEBUG)

def on_message(pgn, data):
    """Receive incoming messages from the bus

    :param int pgn:
        Parameter Group Number of the message
    :param bytearray data:
        Data of the PDU
    """
    print("PGN {} length {}".format(pgn, len(data)))

def main():
    print("Initializing")

    # create the ElectronicControlUnit (one ECU can hold multiple ControllerApplications)
    ecu = j1939.ElectronicControlUnit()

    # Connect to the CAN bus
    # Arguments are passed to python-can's can.interface.Bus() constructor
    # (see https://python-can.readthedocs.io/en/stable/bus.html).
    # ecu.connect(bustype='socketcan', channel='can0')
    # ecu.connect(bustype='kvaser', channel=0, bitrate=250000)
    ecu.connect(bustype='pcan', channel='PCAN_USBBUS1', bitrate=250000)
    # ecu.connect(bustype='ixxat', channel=0, bitrate=250000)
    # ecu.connect(bustype='vector', app_name='CANalyzer', channel=0, bitrate=250000)
    # ecu.connect(bustype='nican', channel='CAN0', bitrate=250000)

    # subscribe to all (global) messages on the bus
    ecu.subscribe(on_message)

    time.sleep(120)

    print("Deinitializing")
    ecu.disconnect()

if __name__ == '__main__':
    main()

A more sophisticated example in which the CA class was overloaded to include its own functionality:

import logging
import time
import can
import j1939

logging.getLogger('j1939').setLevel(logging.DEBUG)
logging.getLogger('can').setLevel(logging.DEBUG)

class OwnCaToProduceCyclicMessages(j1939.ControllerApplication):
    """CA to produce messages

    This CA produces simulated sensor values and cyclically sends them to
    the bus with the PGN 0xFEF6 (Intake Exhaust Conditions 1).
    """

    def __init__(self, name, device_address_preferred=None):
        # old fashion calling convention for compatibility with Python2
        j1939.ControllerApplication.__init__(self, name, device_address_preferred)

    def start(self):
        """Starts the CA
        (OVERLOADED function)
        """
        # add our timer event
        self._ecu.add_timer(0.500, self.timer_callback)
        # call the super class function
        return j1939.ControllerApplication.start(self)

    def stop(self):
        """Stops the CA
        (OVERLOADED function)
        """
        self._ecu.remove_timer(self.timer_callback)

    def on_message(self, pgn, data):
        """Feed incoming message to this CA.
        (OVERLOADED function)
        :param int pgn:
            Parameter Group Number of the message
        :param bytearray data:
            Data of the PDU
        """
        print("PGN {} length {}".format(pgn, len(data)))

    def timer_callback(self, cookie):
        """Callback for sending the IEC1 message

        This callback is registered at the ECU timer event mechanism to be
        executed every 500ms.

        :param cookie:
            A cookie registered at 'add_timer'. May be None.
        """
        # wait until we have our device_address
        if self.state != j1939.ControllerApplication.State.NORMAL:
            # returning true keeps the timer event active
            return True

        pgn = j1939.ParameterGroupNumber(0, 0xFE, 0xF6)
        data = [
            j1939.ControllerApplication.FieldValue.NOT_AVAILABLE_8, # Particulate Trap Inlet Pressure (SPN 81)
            j1939.ControllerApplication.FieldValue.NOT_AVAILABLE_8, # Boost Pressure (SPN 102)
            j1939.ControllerApplication.FieldValue.NOT_AVAILABLE_8, # Intake Manifold 1 Temperature (SPN 105)
            j1939.ControllerApplication.FieldValue.NOT_AVAILABLE_8, # Air Inlet Pressure (SPN 106)
            j1939.ControllerApplication.FieldValue.NOT_AVAILABLE_8, # Air Filter 1 Differential Pressure (SPN 107)
            j1939.ControllerApplication.FieldValue.NOT_AVAILABLE_16_ARR[0], # Exhaust Gas Temperature (SPN 173)
            j1939.ControllerApplication.FieldValue.NOT_AVAILABLE_16_ARR[1],
            j1939.ControllerApplication.FieldValue.NOT_AVAILABLE_8, # Coolant Filter Differential Pressure (SPN 112)
            ]

        # SPN 105, Range -40..+210
        # (Offset -40)
        receiverTemperature = 30
        data[2] = receiverTemperature + 40

        self.send_message(6, pgn.value, data)

        # returning true keeps the timer event active
        return True


def main():
    print("Initializing")

    # create the ElectronicControlUnit (one ECU can hold multiple ControllerApplications)
    ecu = j1939.ElectronicControlUnit()

    # Connect to the CAN bus
    # Arguments are passed to python-can's can.interface.Bus() constructor
    # (see https://python-can.readthedocs.io/en/stable/bus.html).
    # ecu.connect(bustype='socketcan', channel='can0')
    # ecu.connect(bustype='kvaser', channel=0, bitrate=250000)
    ecu.connect(bustype='pcan', channel='PCAN_USBBUS1', bitrate=250000)
    # ecu.connect(bustype='ixxat', channel=0, bitrate=250000)
    # ecu.connect(bustype='vector', app_name='CANalyzer', channel=0, bitrate=250000)
    # ecu.connect(bustype='nican', channel='CAN0', bitrate=250000)
    # ecu.connect('testchannel_1', bustype='virtual')

    # compose the name descriptor for the new ca
    name = j1939.Name(
        arbitrary_address_capable=0,
        industry_group=j1939.Name.IndustryGroup.Industrial,
        vehicle_system_instance=1,
        vehicle_system=1,
        function=1,
        function_instance=1,
        ecu_instance=1,
        manufacturer_code=666,
        identity_number=1234567
        )

    # create derived CA with given NAME and ADDRESS
    ca = OwnCaToProduceCyclicMessages(name, 128)
    # add CA to the ECU
    ecu.add_ca(controller_application=ca)
    # by starting the CA it starts the address claiming procedure on the bus
    ca.start()

    time.sleep(120)

    print("Deinitializing")
    ca.stop()
    ecu.disconnect()

if __name__ == '__main__':
    main()

Credits

This implementation was initially inspired by the CANopen project of Christian Sandberg. Thanks for your great work!

Most of the informations about SAE J1939 are taken from the papers and the book of Copperhill technologies and from my many years of experience in J1939 of course :-)