S7-200 SMART Direct WinCC Communication Without OPC
Achieving reliable direct communication between Siemens S7-200 SMART PLC and WinCC SCADA is a common requirement in industrial automation. This article explains two proven methods that bypass OPC servers, reducing complexity and cost while maintaining stability.
Why Avoid OPC for S7-200 SMART and WinCC?
OPC (OLE for Process Control) is a widely used middleware for data exchange between PLCs and SCADA systems. However, for small to medium applications, adding an OPC server introduces extra licensing costs, configuration effort, and a potential point of failure. Direct communication using native protocols simplifies the architecture and often improves data throughput. The S7-200 SMART PLC does not natively support the S7-300 TCP protocol required by WinCC, but with the right hardware converters, a direct link is possible.
Method 1: ETH PPI Converter
The ETH PPI device converts the PPI (Point-to-Point Interface) port of the S7-200 SMART to Ethernet, emulating the S7-300 TCP protocol. This allows WinCC to communicate as if it were talking to an S7-300 PLC. The setup is straightforward:
- Connect the ETH PPI to the PLC’s PPI port (usually a 9-pin D-sub connector).
- Configure the ETH PPI’s IP address and network parameters using its configuration software.
- In WinCC, add a new driver for “SIMATIC S7-300/400” and set the connection parameters to the ETH PPI’s IP address, rack, and slot (typically rack 0, slot 2 for S7-200 SMART).
This method is popular due to the low cost of ETH PPI modules. However, it occupies the PLC’s PPI port, which might be needed for an HMI or programming device. If the PPI port is already in use, the second method becomes necessary.
⚠️ Note: Some ETH PPI modules require a 24V DC power supply. Always check the manufacturer’s specifications.
Method 2: Multifunction Switch (Protocol Converter)
A multifunction switch (also called a protocol converter or communication adapter) connects to the S7-200 SMART via its Ethernet port and translates the protocol to S7-300 TCP. This method does not use the PPI port, leaving it free for other devices. Key advantages include:
- Supports up to 2 S7-200 SMART PLCs simultaneously (some models support 4).
- Built-in Ethernet switch ports allow daisy-chaining or connecting other Ethernet devices.
- Higher data throughput compared to PPI-based converters.
Configuration is similar to the ETH PPI: set the IP address, map the PLC addresses, and configure WinCC with the corresponding IP and slot numbers. For projects with multiple S7-200 SMART PLCs, this solution offers excellent cost-effectiveness because one device can handle several PLCs and reduce network infrastructure.
| Feature | ETH PPI | Multifunction Switch |
|---|---|---|
| Connection port on PLC | PPI (RS485) | Ethernet |
| Max PLCs supported | 1 | 2 to 4 |
| Built-in switch ports | No | Yes (typically 2-3 ports) |
| PPI port availability | Occupied | Free for other uses |
| Typical cost | Lower | Moderate |
Step-by-Step Configuration in WinCC
Regardless of the hardware chosen, the WinCC configuration follows a similar pattern:
- Open WinCC Explorer and navigate to Tag Management.
- Right-click and add a new driver: SIMATIC S7 Protocol Suite.
- Under the driver, select TCP/IP and create a new connection.
- Set the connection parameters: IP address of the converter, rack number (usually 0), and slot number (2 for S7-200 SMART).
- Create tags with addresses corresponding to the PLC memory areas (e.g., DB1.DBX0.0 for bit memory, MW100 for marker word).
It is important to ensure that the IP address of the converter is in the same subnet as the WinCC PC and that no firewall blocks the TCP port (default 102).
Tips for Stable Communication
- Use shielded Ethernet cables and proper grounding to avoid electromagnetic interference.
- Set a fixed IP address for the converter and the WinCC PC to prevent DHCP-related disconnections.
- Adjust the communication cycle in WinCC based on the number of tags; too short a cycle may overload the network.
- Monitor diagnostic LEDs on the converter to quickly identify link or data exchange issues.
- Update firmware of the converter if available, as manufacturers often release stability improvements.
✅ Both methods have been field-proven in thousands of installations. The choice depends on your specific needs: if the PPI port is free and budget is tight, ETH PPI is ideal. For multi-PLC setups or when the PPI port is occupied, the multifunction switch offers greater flexibility and scalability.
Frequently Asked Questions
Q: Can I connect multiple WinCC stations to one S7-200 SMART using these methods?
A: Yes, but the number of simultaneous connections depends on the converter. Some multifunction switches support up to 4 upper-computer connections.
Q: Do these converters work with other SCADA systems?
A: Generally, any SCADA that supports the S7-300 TCP protocol can communicate through these converters, including third-party systems.
Q: What is the typical data refresh rate?
A: With a properly configured network, refresh times of 100-500 ms for a few hundred tags are achievable. The actual rate depends on the converter performance and network load.
By implementing direct communication, you can streamline your automation system, reduce software dependencies, and achieve a robust data link between S7-200 SMART and WinCC.
