python canopenの使い方【入門レベル】

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Python Canopen

Python Canopen is a powerful module that allows developers to work with CANopen networks using Python programming language. This module simplifies the process of communication between devices in a CANopen network by providing a comprehensive set of tools and utilities.

With Python Canopen, developers can easily create, configure, and manage CANopen nodes, interact with different CANopen devices, monitor and control the network, and exchange data between nodes. This module enables seamless integration of Python applications with CANopen networks, making it an essential tool for anyone working with CANopen devices.

Installation

To install Python Canopen, you can use pip, which is the package installer for Python.

pip install canopen

Once the installation is complete, you can import the module into your Python program.

import canopen

Creating a CANopen Network

The first step in working with Python Canopen is to create a CANopen network. This is done by creating an instance of the Network class and specifying the CAN interface to use.

network = canopen.Network()
network.connect(channel='can0', bustype='socketcan')

Adding CANopen Nodes

After creating the network, you can add CANopen nodes to the network. Each node corresponds to a specific device in the CANopen network.

node = network.add_node(1, 'edsfile.eds')

In the above code, 1 is the node ID, and 'edsfile.eds' is the Electronic Data Sheet (EDS) file for the device. The EDS file contains information about the device’s object dictionary, which defines the available data objects and their attributes.

Configuring the Node

Once you have added a node to the network, you can configure it by setting various parameters. For example, you can set the node’s heartbeat time, which represents how often the node should send heartbeat messages to indicate its presence in the network.

node.heartbeat_time = 1000

Reading and Writing Data

Python Canopen allows you to read and write data to and from CANopen devices easily. You can access the object dictionary of a node and manipulate its data objects.

To read data from a specific object, you can use the read() method.

data = node.sdo[0x1000].read()

To write data to an object, you can use the write() method.

node.sdo[0x1001].write(data)

Monitoring the Network

Python Canopen provides various tools to monitor the network and its nodes. For example, you can monitor the PDOs (Process Data Objects) to track the data exchange between nodes.

def pdo_received(event):
    print(f"PDO received: {event.cob_id}")

network.add_callback(pdo_received, event_type='pdo_received')

In the above code, the pdo_received function is called whenever a PDO is received. The event.cob_id attribute represents the COB-ID (Communication Object Identifier) of the received PDO.

Controlling the Network

Python Canopen also allows you to control the network by starting and stopping it. When the network is started, the nodes in the network become operational and can start exchanging data.

To start the network, you can use the start() method.

network.start()

To stop the network, you can use the stop() method.

network.stop()

Conclusion

Python Canopen provides a convenient and efficient way to work with CANopen networks using Python. Its extensive set of tools and utilities simplifies the process of communication, configuration, and management of CANopen nodes. By leveraging Python’s flexibility and ease of use, developers can seamlessly integrate their applications with CANopen networks. Whether you are a beginner or an experienced developer, Python Canopen is a valuable tool in your arsenal for working with CANopen devices.