Embedded Modbus/TCP gateway design and implementation (1)

With the deepening of the process of development, the realization Enterprise top management network and field control network of seamless connectivity is becoming more and more important.

Based on the quality of production management, and security-related test monitor requires the scene of the instrument can be handled on-site information and timely is the superior monitoring and management of network access and control, and ultimately into the enterprise information management system, unified framework.

At present, constitute the underlying control network of fieldbus technology have access to a wide range of applications.

A variety of fieldbus standards coexist and not compatible with each issue has plagued the industry. The industrial Ethernet applications to control network has become the focus of current research and future trend of development. How to make this kind of network structure and industrial Ethernet technology, the realization of the underlying production and top management of tightly integrated is the current focus of the study.

1 Modbus Protocol and gateway topology

Modbus fieldbus Protocol is Modicon company in 1978, a fieldbus Protocol [1].

Through this agreement, controller, controller with each other through networks and other devices can communicate. The agreement can receive free, Modbus serial link version in occupies a dominant market position on the long term. A large number of products have been run directly or compatible with Modbus serial link version.

Modbus/TCP industrial Ethernet protocol is the 1999 developed a Modbus Protocol version [2], allows the user to access the device via Ethernet.

Protocol of open and easy to learn, make it better than many commercial interest-driven agreement achieved faster development, were numerous third-party product manufacturers, end-users, system integrators of broad support [3].

This article in the design and implementation of an embedded protocol conversion gateway for Modbus/TCP protocol through the traditional serial link communication Modbus fieldbus and Ethernet.

User via Ethernet to the Modbus Devices for data collection and Modbus device for remote access and control. At the gateway also provides Web services capabilities and allow direct through the Web browser to configure the gateway IP address and other information and saved to the gateway's non-volatile memory. Figure 1 is an embedded Modbus/TCP gateway connection diagram.

2 gateway design

Gateway will use the ATMEL AT91RM9200 company produces high-performance 32-bit industrial embedded microprocessor as gateway hardware at the core of the system.

Gateway software system will transplant μ S-C/O I I embedded real-time operating system and the implementation of the TCP/IP protocol stack, on the basis of application-layer program design. Gateway's overall design structure as in Figure 2. Gateway design will use open source embedded operating system and the TCP/IP protocol stack, thus obtaining a more cost-effective basis to achieve the best scalability.

3 hardware design

AT91RM9200 is famous semiconductor manufacturers ATMEL force push based on ARM920T core industrial embedded microprocessors, to the maximum, minimum power consumption, low-cost embedded system provides a complete solution [4], which in addition to the traditional advantage with ARM microprocessor, its performance, reliability, and scalability were all significantly exceeded the normal commercial grade ARM7 core embedded microprocessors.

Hardware system structure shown in Figure 3.

[1] [2] [3]