What is CanOPEN and CanBUS? (Controller Area Network)

Our topic today is the CAN protocol, which is one of the most used communication protocols in PLC systems. You will hear the word "node" in this article, but do not think of it as a crypto project. I just wanted to make a bad joke. :)

The subject I will explain is long and detailed. Let's get started without wasting time.

What is CanBUS?

CAN is a communication system is used in many industrial applications. Systems used in daily life such as automobiles, elevators and smart home systems communicate with the CanBUS communication system. The biggest reasons for its preference are that it minimizes cable mess and cable weight and is very cost-effective. Another important feature is that the margin of error is very low.

Let's explain this with a simple example; A lot of digital and analog information may be needed for a device to operate. If we were to take the simplest one, it is an engine. A motor needs analog information such as speed and digital information such as start-stop through a driver. Thanks to these inputs, it transfers analog information such as current, voltage, instantaneous speed, and digital information such as running, stopping, malfunction. However, since this information will be transferred between the PLC and the driver via cables, the transfer of each information (PLC to driver, driver to PLC) requires separate cables. This cabling means extra cost. This is where CAN comes into play and provides information exchange between PLC and Driver via only 3 cables.

What is CanOPEN?

CANopen is a control network protocol and is used in automatic control systems. CANopen is based on a CAN (Controller Area Network) protocol and is integrated with a unified application layer of this protocol. CANopen facilitates the interaction and data flow of devices by providing communication in control systems. In this way, more efficient communication and better performance are achieved in control systems.

There are many advantages to using CANopen. The main ones are:

1. CANopen is a control network protocol that can allow many different devices to interact with each other. In this way, it enables communication in control systems and facilitates data sharing between devices.
2. CANopen is based on a CAN protocol and integrated with a unified application layer of this protocol. In this way, the use of CANopen includes the advantages of the CAN protocol and provides more efficient communication in control systems.
3. CANopen supports the use of many different devices together and ensures compatibility between devices. In this way, it facilitates the interaction of devices with each other and data sharing in control systems.
4. CANopen can be used in many different applications and has a wide range of applications. In this way, the use of CANopen can be customized according to the needs of control systems and a better performance can be achieved in control systems.

Thanks to these advantages, the use of CANopen provides more efficient communication and better performance in control systems. For this reason, the use of CANopen is often preferred in automatic control systems.

What is the structure of the CAN line?

CAN communication is provided with two cables, the use of twisted cable significantly reduces the magnetic field effect. Cable diameter can be selected between 0.34 mm2 and 0.6 mm2, line (cable) length is important in choosing the communication speed. To ensure electromagnetic compatibility in physical signal transmission, two symmetrical signals are used (CAN-H, CAN-L).

The physical structure of the CAN line may vary depending on some special situations. While it is necessary to use a resistor in the version called High Speed Can, if Low Speed Can is used, resistance may not be needed. After giving the basic connection types and definitions, I plan to explain these issues in detail. So for now this information is enough for us.

What is a Master / Slave Device?

The terms Master and Slave are used in the CANopen communication protocol. These terms are related to determining the behavior of the device on the communication line. The device called master; It has critical powers such as starting or stopping CANopen communication, controlling the operating status of slave devices on the line, shutting down or restarting slave devices, and making or changing the settings of slave devices.

To give a very simple example for the master device, the Electronic Control Unit (ECU) in an automobile is the element that processes data, makes decisions and controls other devices on the line. In industrial applications, this task is usually performed by PLC or industrial PC.

What is Node ID and Baud Rate?

Each device in the communication line is called a node. Every node on the CANopen communication line, that is, every device on the line, must have an "ID" identification number. This identification number must be different for each device, that is, unique. If more than one device uses the same Node ID, errors and problems may occur in data transmission or communication. While there may be 32 nodes, that is, devices, in the Low-Speed Can line, there can be 110 devices in the High-Speed Can line.

Baud rate is a term used throughout communication systems. It is the number of pulses per second produced or received by devices on the line. CANopen communication speed depends on the physical connection you will use, that is, the cable length. As the cable length increases, the communication speed you can use decreases. In addition, all devices on the line must be able to operate with the same baud rate. If the communication speed of any element on the line is different, communication problems occur.

I tried to explain how effective and useful the CAN protocol is and how we use it. It is one of the most important communication protocols that everyone who is interested in automation, is an automation software developer or wants to be one should know. I also used it in many projects. I hope you liked my article. Please don't forget to comment, vote and check out my other articles.

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