DeviceNet to PROFIBUS Gateway: Integrate Omron Servos with Siemens PLC
In modern manufacturing facilities, it is common to find equipment from different vendors that use incompatible communication protocols. A typical scenario involves a Siemens PLC acting as a PROFIBUS master, while an Omron servo drive only understands DeviceNet. Without a bridge, these devices cannot exchange data, leading to isolated automation islands. A DeviceNet to PROFIBUS gateway solves this problem by translating between the two protocols in real time, enabling seamless integration without replacing existing hardware.
This article explores the technical aspects, practical benefits, and implementation considerations of using such a gateway. We will draw on a real-world example from an injection molding workshop in Zhejiang, China, where a gluing robot cell was successfully upgraded.
Key Takeaway: A DeviceNet to PROFIBUS gateway can reduce retrofit costs by up to 80% compared to replacing all servo drives, while maintaining real-time performance and simplifying wiring.
The Communication Challenge in Mixed-Vendor Systems
Industrial communication protocols like PROFIBUS and DeviceNet serve similar purposes but are fundamentally different in their physical layers, data formats, and network management. PROFIBUS, widely used in Siemens automation systems, follows the IEC 61158 standard and typically operates over RS-485 with a maximum of 126 nodes. DeviceNet, based on the Common Industrial Protocol (CIP), uses CAN technology and supports up to 64 nodes. Direct communication between a PROFIBUS master and a DeviceNet slave is impossible without a protocol converter.
In the Zhejiang factory, the existing setup included a Siemens S7-300 PLC (PROFIBUS DP master) and several Omron R88D-KN series servo drives with DeviceNet interfaces. The original control method used discrete I/O wiring, which was cumbersome and limited diagnostic capabilities. The goal was to replace an aging spraying machine with a new gluing robot while reusing the Omron servos to save costs.
How the DeviceNet to PROFIBUS Gateway Works
The gateway acts as a bidirectional translator. On the PROFIBUS side, it appears as a standard slave device to the Siemens PLC. On the DeviceNet side, it functions as a master, controlling the Omron servo drives. The internal mapping table defines how data is exchanged between the two networks.
The process is straightforward:
- The PLC writes control commands (e.g., target position, speed) to its output area assigned to the gateway.
- The gateway converts these PROFIBUS data frames into DeviceNet explicit or I/O messages and sends them to the appropriate servo drive.
- The servo drive responds with status information (actual position, torque, alarms), which the gateway translates back into PROFIBUS input data for the PLC.
This data exchange occurs within a few milliseconds, ensuring that the robot’s gluing trajectory remains smooth and accurate. The gateway handles all protocol intricacies, including baud rate negotiation, error checking, and retries.
Hardware Setup and Configuration
Physical installation is simple. The gateway typically has two communication ports: a 9-pin D-sub connector for PROFIBUS and a 5-pin open-style connector for DeviceNet. Wiring involves connecting the PROFIBUS cable from the PLC to the gateway, and the DeviceNet trunk line from the gateway to the servo drives. Power is usually supplied via the DeviceNet network or an external 24V DC source.
Configuration is often code-free, using DIP switches or a web interface. Key parameters include:
| Parameter | Description | Typical Setting |
|---|---|---|
| PROFIBUS Node Address | Unique station address on the PROFIBUS network | 3 (example) |
| DeviceNet MAC ID | Node address on the DeviceNet network | 0 (master) |
| Baud Rates | Communication speed for both networks | PROFIBUS: 1.5 Mbps; DeviceNet: 500 kbps |
| I/O Data Sizes | Number of bytes exchanged with each servo | 4 bytes in / 4 bytes out per axis |
In the Zhejiang project, the gateway was configured to map the PLC’s control word and target position directly to the servo’s corresponding DeviceNet objects. This eliminated the need for custom programming and reduced commissioning time significantly.
Performance and Real-Time Considerations
One of the main concerns with protocol gateways is latency. In motion control applications, excessive delay can cause trajectory errors or instability. Modern gateways are designed with high-speed processors and optimized firmware to minimize latency. In the described application, the total round-trip time (PLC to servo and back) was measured at under 5 ms, which is acceptable for most robotic gluing tasks.
The gateway also supports cyclic data exchange, ensuring deterministic updates. The PROFIBUS DP cycle time can be set as low as 1 ms, while DeviceNet I/O polling rates can be configured per slave. By aligning these cycles, the system achieves consistent performance.
Cost Savings and ROI
The economic advantage of using a gateway is substantial. Replacing an Omron servo drive with a PROFIBUS-compatible model can cost two to three times more than the gateway itself, not including installation labor and mechanical modifications. In the Zhejiang factory, the total retrofit cost was reduced by approximately 75% compared to a full servo replacement.
Additional savings come from reduced wiring. Instead of dozens of discrete I/O wires, only two network cables are needed. This simplifies troubleshooting and lowers the risk of wiring faults. The factory also reported a decrease in scrap rate due to improved diagnostic capabilities—servo alarms are now instantly communicated to the PLC, allowing immediate shutdown and preventing defective products.
Application Scenarios and Industry Use
DeviceNet to PROFIBUS gateways are not limited to Omron and Siemens combinations. They are widely used in any environment where legacy DeviceNet devices need to be integrated into a PROFIBUS-based control system. Common examples include:
- Connecting Allen-Bradley PowerFlex drives (DeviceNet) to Siemens PLCs.
- Integrating DeviceNet-based sensors and I/O blocks into a PROFIBUS network.
- Retrofitting older machines with DeviceNet-enabled components into modern PROFIBUS lines.
In the automotive industry, such gateways are used to link robotic welding cells with centralized PLCs. In packaging, they enable communication between multi-vendor conveyor systems. The flexibility of protocol conversion allows plants to gradually upgrade their control systems without discarding functional equipment.
Selection Criteria for a Gateway
When choosing a DeviceNet to PROFIBUS gateway, consider the following factors:
| Feature | Importance |
|---|---|
| Certification | Ensure the gateway is certified by PROFIBUS & PROFINET International (PI) and ODVA for reliable interoperability. |
| Data Throughput | Check the maximum I/O data size per slave; typical requirements are 8-32 bytes per servo. |
| Configuration Ease | Look for tools like GSD files for PROFIBUS and EDS files for DeviceNet, plus a user-friendly mapping interface. |
| Diagnostic LEDs | Status indicators for both networks simplify troubleshooting. |
| Environmental Rating | For harsh industrial environments, select a gateway with IP20 or higher protection and wide temperature range. |
Step-by-Step Integration Guide
Based on the Zhejiang project, here is a simplified integration process:
- Network Planning: Assign node addresses and baud rates. Ensure no conflicts on either network.
- Hardware Connection: Connect the PROFIBUS cable to the PLC and gateway, and the DeviceNet cable to the gateway and servo drives. Terminate both networks properly.
- Gateway Configuration: Set the PROFIBUS slave address via DIP switches. Use the gateway’s configuration software to define the DeviceNet scan list and I/O mapping.
- PLC Programming: Import the gateway’s GSD file into the PLC engineering tool (e.g., TIA Portal). Configure the I/O areas and write control logic.
- Testing: Verify communication by monitoring live data. Test emergency stop and alarm handling.
In the factory, the entire setup took less than a day, and the gateway has been running without communication faults for over six months.
Future-Proofing and Scalability
While PROFIBUS and DeviceNet are considered mature technologies, they remain prevalent in many industries. A gateway not only solves immediate integration needs but also provides a migration path. For instance, if the PLC is later upgraded to PROFINET, a PROFIBUS-to-PROFINET proxy can be used in conjunction with the existing gateway, preserving the investment in DeviceNet devices.
Moreover, the gateway’s mapping flexibility allows easy addition of more servo drives or other DeviceNet nodes without major reprogramming. This scalability is crucial for expanding production lines.
Conclusion
A DeviceNet to PROFIBUS gateway is a practical, cost-effective solution for integrating Omron servo drives with Siemens PLCs. It eliminates protocol barriers, reduces wiring complexity, and preserves legacy equipment. With real-time performance and easy configuration, it is an essential tool for any automation engineer dealing with mixed-vendor systems. As industrial communication continues to evolve, such gateways will remain vital for bridging the gap between old and new technologies.
