S7-200 SMART G2 Wireless Profinet Communication Test: Stable & Reliable

In many industrial environments, multiple PLCs are spread across a workshop floor, often separated by tens or even hundreds of meters. When these controllers need to exchange data, traditional wired Ethernet cabling can be a nightmare—costly, time-consuming, and messy. Wireless communication offers a clean, flexible alternative, and with modern industrial wireless terminals, it’s now possible to achieve the same deterministic performance as a cable. This article walks through a real-world test of wireless Profinet communication between two Siemens S7-200 SMART G2 PLCs, highlighting the setup, configuration, and results.

Why Go Wireless with Profinet?

Profinet is a leading industrial Ethernet standard, known for its speed and determinism. It’s widely used in factory automation, process control, and motion control applications. Traditionally, Profinet relies on wired connections, but advances in wireless technology now allow reliable wireless Profinet communication. This is especially useful for moving equipment, remote I/O stations, or areas where cabling is impractical. A wireless Profinet system can reduce installation costs, simplify maintenance, and increase flexibility for future layout changes.

The key is to use a wireless terminal specifically designed for Profinet, not a generic Wi-Fi bridge. These devices handle the protocol’s real-time requirements, ensuring low latency and jitter. In this test, we used a pair of industrial wireless communication terminals that seamlessly replace a cable, supporting Profinet RT (Real-Time) and standard TCP/IP traffic.

Test Setup Overview

The goal was to establish a wireless Profinet link between two Siemens S7-200 SMART G2 PLCs (model ST32) and verify data exchange. One PLC acted as the IO controller (master), the other as an IO device (slave). The wireless terminals were connected directly to the PLCs’ Ethernet ports, creating a transparent wireless tunnel.

The wireless terminals operate in the 2.4 GHz or 5 GHz band (depending on regional settings) and use proprietary protocols to ensure reliable Profinet communication. They support automatic frequency hopping to avoid interference, making them suitable for harsh industrial environments.

Wiring and Physical Setup

Connecting the hardware is straightforward. Each wireless terminal has an RJ45 port and a power terminal block. Simply connect an Ethernet cable from the PLC’s LAN port to the terminal’s RJ45 port. Then supply 24 VDC power to the terminal. Attach the provided antennas, and the physical installation is complete. No special configuration of the wireless terminals is needed—they work as a transparent bridge, automatically pairing with each other out of the box.

For this test, the two PLCs and wireless terminals were placed about 50 meters apart, with a clear line of sight. The antennas were oriented vertically for optimal signal propagation. In a real factory, you might mount the terminals inside a control cabinet with external antennas for better range.

Profinet Configuration in TIA Portal

The S7-200 SMART G2 uses the STEP 7-Micro/WIN SMART software for programming and configuration. The Profinet setup involves defining one PLC as the controller and the other as an intelligent IO device. Here’s a step-by-step breakdown:

Configuring the IO Device (Slave)

1. Create a new project for the slave PLC (e.g., PLC_2).
2. Go to Tools > PROFINET and set the device role to Intelligent IO device.
3. Assign the IP address: 192.168.2.2, subnet mask 255.255.255.0, and station name “plc200smart2”.
4. Click Next and add a transfer area. Define the input/output data sizes (e.g., 8 bytes in, 8 bytes out).
5. Export the GSD file. This file describes the device’s Profinet capabilities and will be imported into the controller project.
6. Write a simple program in the slave PLC to map the transfer area to physical I/O or internal memory. For example, move the received data to output coils and copy input states to the send buffer.

Configuring the IO Controller (Master)

1. Create a new project for the master PLC (e.g., PLC_1).
2. Set the device role to Controller.
3. Assign the IP address: 192.168.2.1, subnet mask 255.255.255.0, station name “plc200smart1”. Ensure it’s on the same subnet as the slave.
4. Import the GSD file from the slave project. Go to Tools > PROFINET, click Import GSD, and select the file.
5. Add the imported device to the controller’s network. The software will show the available IO device.
6. Configure the update time (e.g., 2 ms) and data transfer areas to match the slave’s definition.
7. Generate the configuration and write the controller program. For testing, you can simply map the input data from the slave to local outputs, and local inputs to the slave’s outputs.

After downloading the configurations to both PLCs, the Profinet connection should establish automatically. The wireless terminals are transparent, so the PLCs behave as if they are directly connected by a cable.

Testing and Results

With both PLCs powered and the wireless terminals linked, we performed a simple I/O mirroring test. When a digital input on PLC_1 was activated, the corresponding output on PLC_2 turned on instantly. Similarly, toggling an input on PLC_2 triggered an output on PLC_1. The response was immediate, with no perceptible delay.

We also monitored the Profinet diagnostic status in the software. The connection remained stable with no dropped packets or errors over several hours. The wireless terminals maintained a strong signal, even when we introduced mild obstructions (like moving a metal cart between them). The system automatically adjusted to maintain the link.

In a more demanding test, we increased the data size to 64 bytes in each direction and added a cyclic communication watchdog. The wireless link handled the load without any issues, proving its suitability for typical industrial control tasks such as conveyor synchronization, pump control, or remote monitoring.

Key Benefits of This Wireless Solution

• Plug-and-play simplicity: No complex wireless configuration. The terminals pair automatically.
• Profinet transparency: The PLCs see a standard Ethernet connection; no special function blocks or protocol conversion needed.
• Long range: Up to 2 km line-of-sight, with options for external high-gain antennas for even greater distances.
• Industrial robustness: Designed for harsh environments with wide temperature range, vibration resistance, and EMI immunity.
• Cost-effective: Eliminates expensive cable trays, trenching, and ongoing maintenance of wired infrastructure.

Practical Considerations for Deployment

While the test was straightforward, real-world installations require attention to a few details. Always ensure a clear line of sight between antennas, or use a repeater if obstacles are unavoidable. Mount the wireless terminals as high as possible to avoid ground clutter. In electrically noisy environments, use shielded Ethernet cables and proper grounding. Also, consider network security: although the wireless link is encrypted, it’s wise to isolate the Profinet network from the corporate LAN using a firewall or VLAN.

For larger systems with multiple slaves, you can use a wireless access point topology, but the transparent bridge approach works best for point-to-point or small star configurations. Always test the wireless link under full load conditions before commissioning.

Conclusion

Wireless Profinet communication is no longer a futuristic concept—it’s a practical, reliable solution for today’s industrial automation needs. The test with S7-200 SMART G2 PLCs and dedicated wireless terminals demonstrated stable, low-latency data exchange over a significant distance. This approach can save time and money while providing the flexibility to adapt to changing production layouts. Whether you’re retrofitting an old facility or designing a new one, wireless industrial communication deserves serious consideration.