Python Durand - CANopen Responder Device Library

A CANopen library to implement responder nodes.

Backends:

• CAN interfaces via python-can

Synopsis

• Pure Python implementation
• Licensed under MIT (2021 Günther Jena)
• Source code hosted on GitHub.com
• Tested on Python 3.7, 3.8, 3.9, and 3.10
• Unit tested with pytest, coding style enforced with Black, static type checking with mypy, static code analysis with Pylint, documentation generated with Sphinx
• Supports CiA301 (EN 50325-4)

Feature List

• Object Dictionary:
  • Provides callbacks for validation, update, download, and read operations
  • Supports records, arrays, and variables
• EDS Support:
  • Dynamic generation of EDS files
  • Automatically provided via object 0x1021 ("Store EDS")
• SDO Servers:
  • Supports up to 128 SDO servers
  • Expedited, segmented, and block transfer for upload and download
  • Dynamically configurable COB-IDs
  • Custom upload and download handlers supported
• PDO Support:
  • Up to 512 TPDOs and 512 RPDOs
  • Dynamically configurable
  • Transmission types: synchronous (acyclic and every nth sync) and event-driven
  • Supports inhibit time
• EMCY Producer Service:
  • Dynamically configurable COB-ID
  • Supports inhibit time
• Heartbeat Producer Service:
  • Dynamically configurable
• NMT Slave Service:
  • Boot-up service
  • Callback for state change provided
• SYNC Consumer Service:
  • Dynamically configurable COB-ID
  • Callback for received sync provided
• CiA305 Layer Setting Service:
  • Supports fast scan
  • Configurable bitrate and node ID
  • Identify remote responder supported
• CAN Interface Abstraction:
  • Full support for python-can
  • Automatic CAN ID filtering by subscribed services
• Scheduling:
  • Supports threaded and async operation

TODO:

• Build object dictionary via reading an EDS file
• Support MPDOs
• TIME consumer service
• Up- and download handler as I/O streams

Examples

Creating a Node:

import can
from durand import CANBusNetwork, Node, Variable, Record, DatatypeEnum

bus = can.Bus(bustype='socketcan', channel='vcan0')
network = CANBusNetwork(bus)
node = Node(network, node_id=0x01)

Congratulations! You now have a CiA-301 compliant node running. The Layer Setting Service is also supported out of the box.

Adding Objects:

od = node.object_dictionary

# Add variable at index 0x2000
od[0x2000] = Variable(DatatypeEnum.UNSIGNED16, access='rw', value=10, name='Parameter 1')

# Add record at index 0x2001
record = Record(name='Parameter Record')
record[1] = Variable(DatatypeEnum.UNSIGNED8, access='ro', value=0, name='Parameter 2a')
record[2] = Variable(DatatypeEnum.REAL32, access='rw', value=0, name='Parameter 2b')
od[0x2001] = record

Accessing Values:

The objects can be read and written directly by accessing the object dictionary:

print(f'Value of Parameter 1: {od.read(0x2000, 0)}')
od.write(0x2001, 1, value=0xAA)

Adding Callbacks:

A more event-driven approach is to use callbacks. The following callbacks are available:

• validate_callbacks: Called before a value in the object dictionary is updated
• update_callbacks: Called when the value has been changed (via od.write or via CAN bus)
• download_callbacks: Called when the value has been changed via CAN bus
• read_callback: Called when an object is read (return value is used)

od.validate_callbacks[(0x2000, 0)].add(lambda v: v % 2 == 0)
od.update_callbacks[(0x2001, 2)].add(lambda v: print(f'Update for Parameter 2b: {v}'))
od.download_callbacks[(0x2000, 0)].add(lambda v: print(f'Download for Parameter 1: {v}'))
od.set_read_callback(0x2001, 1, lambda: 17)

PDO Mapping:

PDOs can be dynamically mapped via the SDO server or programmatically. The PDO indices start at 0.

node.tpdo[0].mapping = [(0x2001, 1), (0x2001, 2)]
node.tpdo[0].transmission_type = 1  # Transmit on every SYNC

node.rpdo[0].mapping = [(0x2000, 0)]
node.tpdo[0].transmission_type = 255  # Event-driven (processed when received)

Installation

pip install durand

Credits

This library would not be possible without:

• python-canopen: CANopen library (by Christian Sandberg)
• python-can: CAN interface library (by Brian Thorne)