“When you first take on industrial equipment, the three letters CANopen feel like a threshold.”“In fact, it’s not that mysterious; it just needs someone to guide you in.”—— From the blood and tears of a bald engineer

🟧 1. Why Learn CANopen?

If you are working on:

• AGVs, small vehicles, AMRs

• Robotic arms

• Motor drivers

• Sensor networks

• PLC peripheral expansion

• Industrial robots…you can hardly escape CANopen.

Why is it so popular? In one sentence:

Because the most important thing in an industrial site is: stability.

The biggest features of CANopen are:

• Strong anti-interference capability

• High bus reliability

• Easy expansion with multiple nodes

• Stable real-time performance

• Independent of operating systems

No complex TCP handshakes, no chaotic address conflicts like RS-485. As long as you do the wiring and terminal resistors correctly, it can run stably for many years.

This is why:AGV motion control almost exclusively uses CANopen.

🟧 2. What is the Relationship Between CAN and CANopen?

One of the most confusing points for beginners:

CANopen is not CAN! CAN is the physical layer & data link layer CANopen is a protocol family built on top of CAN

It can be understood this way:

Level	Meaning
CAN (Lower Layer)	Responsible for sending 8-byte data. Similar to “the courier is only responsible for delivering the package.”
CANopen (Upper Layer)	Specifies what data to include, how to interpret it, and when to send it. Similar to “the recipient address and item list on the delivery note.”

So:

• CAN is the pipeline

• CANopen is the specification

To make the driver “move,” it is not enough to just send raw data via CAN; you need CANopen to tell it whether this 8-byte data is a “speed command” or a “control word.”

🟧 3. What Components Make Up CANopen?

The CANopen system actually consists of 6 main components:

1. Object Dictionary

2. SDO Service (Read/Write Parameters)

3. PDO Channels (Real-time Control)

4. NMT (Node Management)

5. Heartbeat

6. SYNC (Synchronization)

To summarize in one sentence:

SDO is used to read and write parameters, PDO is used for real-time control. NMT manages states, SYNC manages rhythm, and Heartbeat manages disconnections.

As long as you remember this sentence, you have already mastered 50% of the basics.

🟧 4. What is CANopen Suitable For (and Not Suitable For)?

✔ Very Suitable For:

• Motor control (CiA402)

• Multi-driver synchronized motion

• Sensor networks

• AGV / AMR chassis

• Actuators & industrial subsystems

✘ Not Suitable For:

• Large data volume transmission (e.g., images)

• High-speed motion control (>10kHz synchronization, EtherCAT is recommended)

• Complex network topologies (not as good as Ethernet protocols)

In one sentence—CANopen is positioned as a “reliable medium-speed industrial control bus.”.

🟧 5. Common Roles in CANopen: What are Node ID, Index, and COB-ID?

📌 Node ID: Node Number

Values range from 1 to 127 Each driver, sensor, or I/O module is considered a Node.

📌 Index / Sub-index: Object Dictionary Number

For example:

• 0x6040 — Control word

• 0x6041 — Status word

• 0x6060 — Mode

• 0x607A — Target position

• 0x60FF — Target speed

These are like “parameter addresses.”

📌 COB-ID: ID of CAN Message

CANopen messages are defined based on COB-ID:

• SDO: 0x600 + NodeID / 0x580 + NodeID

• PDO: 0x180, 0x200, 0x280, 0x300 …

Knowing this allows you to analyze packet captures.

🟧 6. What Does a Minimal Running CANopen System Look Like?

A minimal demo includes:

• 1 CAN cable (CANH, CANL)

• 2 120Ω terminal resistors

• 1 PC (your development machine)

• 1 CAN to USB converter (e.g., PEAK-CAN)

• 1 driver (supports CANopen)

Once you connect the wires properly, insert the terminal resistors, and ensure the baud rate is consistent— you can run SDO and PDO.

🟩 7. Practical: Get Your First CANopen Communication Running in 5 Minutes

Here is the initial “Hello world.”

📌 Step 1: Install python-canopen

pip install canopenpip install python-can

📌 Step 2: Connect Your CAN Device

Using PEAK-CAN as an example:

import canopennetwork = canopen.Network()network.connect(bustype='pcan', channel='PCAN_USBBUS1', bitrate=500000)

📌 Step 3: Add a Node (Assuming Node ID=8)

node = network.add_node(8, "device.eds")

📌 Step 4: Read Device Information

manufacturer = node.sdo[0x1008].rawrevision = node.sdo[0x100A].rawprint("Device Name:", manufacturer)print("Version:", revision)

Output similar to:

Device Name: XYZ Servo DriveVersion: V1.23This is your first CANopen SDO!

🟧 8. Next Article Preview

“The 8 Core Concepts of CANopen: Explained with Comics for Engineers”