Introduction

In industrial automation and motion control, engineers face a core challenge: how to efficiently and reliably connect distributed sensors, valves, indicator lights, and motors across the factory floor to a central controller (e.g., a PLC).

The traditional "point-to-point wiring" approach results in massive cable quantities, complex wiring, difficult fault troubleshooting, and extremely poor scalability. Alternative solutions using expensive proprietary control systems often lack the flexibility to adapt to rapidly changing production demands.

The market urgently needs a standard, flexible, and cost-effective solution that can manage field I/O signals like building blocks through a single high-speed bus, while remaining compatible with mainstream programming platforms.

The CANopen distributed I/O solution was born for this purpose. And the M31-U-CAN series from Chengdu Ebyte Electronic Technology Co., Ltd. stands as an outstanding representative of this technology

Product Overview: CANopen Slave, Flexible Expansion, Standard Connection

The M31-U-CAN series is a CANopen slave module launched by Chengdu Ebyte Electronic Technology Co., Ltd. It does not perform complex logic operations itself; instead, it faithfully executes "acquisition" and "output" tasks, integrating field sensors and actuators into the CANopen network.

The series includes three models covering the most common I/O combination requirements:

User Pain Points Solved

• Engineers seeking standardization: CANopen is an international standard protocol supported by mainstream PLCs and motion controllers. With M31-U-CAN, engineers can break free from proprietary protocols and enjoy the convenience of standardization.

• System integrators needing flexible expansion: Modular design allows users to add or remove I/O points as project requirements change, without replacing the entire system.

• Project managers worried about field wiring: Consolidating all I/O signals onto a single CAN bus reduces signal wires from hundreds down to just two (CAN_H and CAN_L), with differential signals offering exceptional noise immunity.

• CODESYS developers: The M31-U-CAN integrates seamlessly with the CODESYS development environment by loading the .eds device description file, achieving true plug-and-play.

Features and Model Comparison

Common Features Across All Three Models

• Standard CANopen Slave: Fully complies with CiA (CAN in Automation) standards, compatible with any standard CANopen master.

• Flexible Expansion: The host itself is one node. Through a modular structure, it supports up to 16 IO expansion modules (including the host), with a total of 256 I/O points.

• Rich IO Type Support:

• DI (Digital Input): Supports NPN/PNP active input, voltage range 12V-24V.

• DO (Digital Output): Available in relay (M31-AXAX) and transistor (M31-AXEX) options.

• AI (Analog Input): Supports 0-20mA / 4-20mA differential current input.

• Multiple Industrial-Grade Protections: Complies with EMC Level 3 protection standards, featuring electrostatic protection, surge protection, reverse polarity protection. IO input/output and power supply are fully isolated. CE certified.

• Object Dictionary: Exposes all functions and parameters, enabling automatic identification and configuration by the master — the foundation of CANopen plug-and-play.

• PDO and SDO Communication:

• PDO (Process Data Object): For high-speed, real-time transmission of I/O status.

• SDO (Service Data Object): For configuring device parameters (e.g., filter time, fault output status).

• Hardware Configuration: DIP switches on the device for easy node address and CAN baud rate setting.

• CODESYS Support: Detailed documentation explains how to load the .eds file and add the device in CODESYS.

• Fail-Safe Output: Supports offline IO fault output — maintains current output or switches to a preset state when communication is interrupted.

Model Comparison

Selection Guide

Technical Specifications

Application Scenarios

Scenario ①: Smart Factory Assembly Lines

Pain Point: Large numbers of scattered sensors (e.g., photoelectric switches, proximity sensors) and actuators (e.g., cylinder solenoid valves, indicator lights) need to be collected and controlled.

Solution: Install M31-AXAX8080G-U-CAN (relay output) or M31-AXEX8080G-U-CAN (transistor output) at each station on the assembly line to control solenoid valves or indicators, communicating with the main PLC via the CAN bus.

Scenario ②: Renewable Energy Equipment Monitoring

Pain Point: Remote acquisition and control of analog signals such as temperature, voltage, and current from photovoltaic inverters and wind turbines.

Solution: Use M31-AFAX4440G-U-CAN — its 4 AI channels can directly collect 4-20mA or 0-10V sensor signals, while 4 DO channels control cooling fans or alarms. CANopen's high noise immunity makes it ideal for harsh environments.

Scenario ③: Packaging Machinery

Pain Point: High-frequency, fast, and precise control of multiple solenoid valves and cylinder actions.

Solution: The M31-AXEX8080G-U-CAN's 8 transistor outputs offer microsecond-level response speed and virtually unlimited lifespan, perfect for driving proportional valves or high-frequency solenoid valves on high-speed packaging lines.

Scenario ④: Building Automation

Pain Point: Centralized control and status monitoring of building lighting, HVAC, and fresh air systems.

Solution: Install M31-AXAX8080G-U-CAN units in distribution rooms on each floor, using relay outputs to control lighting circuits and DI inputs to read contactor status, all connected to the central control system via the CAN bus.

EBYTE Core Advantages

FAQ

Q1: What is the difference between M31-AXAX8080G-U-CAN and M31-AXEX8080G-U-CAN? Both are 8DI+8DO.

A: The core difference lies in the DO (Digital Output) type:

• M31-AXAX: Output is Relay. Relays are mechanical switches offering high surge tolerance and the ability to handle larger currents (ideal for inductive loads like contactors and motors). The trade-offs are slower switching speed and limited mechanical lifespan.

• M31-AXEX: Output is Transistor (PNP). Transistors are electronic switches offering extremely fast switching speed (suitable for high-frequency operation), no contact wear, and virtually unlimited lifespan. The trade-off is slightly lower current driving capability. Your choice depends on the load type and switching frequency.

Q2: What CAN baud rates do these three models support?

A: They support 1000k, 500k, 250k, 125k, 100k, 50k, 20k, 10k bps and more. The factory default is 1000kbps. Baud rate is configured via DIP switches on the device.

Q3: How to configure the node address of the M31-U-CAN?

A: Configured via a 10-position DIP switch on the device. The first 3 positions set the CAN baud rate, and the last 7 positions set the node address (valid range 0~127). Please refer to the product manual for details.

Q4: How many expansion modules can this device support?

A: Up to 16 IO expansion modules (including the host). This means your system can have up to 16 independent IO modules cascaded via the internal bus. Expansion modules are separate accessories (e.g., M31-GAFAX4440-U, M31-GAXAX8080-U) and must be purchased separately.

Q5: How to add the M31-AFAX4440G-U-CAN device in CODESYS?

A: The documentation provides detailed steps:

1. Download and prepare the .eds device description file (M31-xxxxxxxx-U-CAN.eds).

2. In CODESYS, select "Tools" -> "Device Repository" -> "Install", and import the .eds file.

3. In the project tree, right-click CANopen_Manager, select "Add Device".

4. Search for "M31" in the search box, find and add the M31-xxxxxxxx-U-CAN device.

The M31-U-CAN series is Ebyte's CANopen distributed IO solution purpose-built for industrial field control. With "standard protocol, modular expansion, rich IO types, and industrial-grade reliability" as its core highlights, it precisely solves the pain points of complex wiring, poor scalability, and difficult integration that engineers face when connecting field devices to central controllers.