Integration with existing code

Sometimes you need to use this library together with some existing code base or you have CAN drivers not supported by python-can. This chapter will cover some use cases.

Re-using a bus

If you need to interact with the CAN-bus outside of this library too and you want to use the same python-can Bus instance, you need to tell the Network which Bus to use and also add the to your existing can.Notifier.

Here is a short example:

import canopen
import can

# A Bus instance created outside
bus = can.interface.Bus()

network = canopen.Network()
# Associate the bus with the network
network.bus = bus

# Add your list of can.Listener with the network's
listeners = [can.Printer()] + network.listeners
# Start the notifier
notifier = can.Notifier(bus, listeners, 0.5)

Using a custom backend

If the python-can package does not have support for your CAN interface then you need to create a sub-class of canopen.Network and provide your own means of sending messages. You also need to feed incoming messages in a background thread to canopen.Network.notify().

Here is an example:

import canopen

class CustomNetwork(canopen.Network):

    def connect(self, *args, **kwargs):
        # Optionally use this to start communication with CAN

    def disconnect(self):
        # Optionally use this to stop communincation

    def send_message(self, can_id, data, remote=False):
        # Send the message with the 11-bit can_id and data which might be
        # a bytearray or list of integers.
        # if remote is True then it should be sent as an RTR.

network = CustomNetwork()

# Should be done in a thread but here we notify the network for
# demonstration purposes only
network.notify(0x701, bytearray([0x05]), time.time())