Open Source Modbus OPC XML-DA

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Welcome to OSMOX. Our goal is to publish an open tool for data acquisition and supervisory control of MODBUS devices. OSMOX is an OPC XML-DA server based on OpenDA.



OPC Foundation is an joint effort of over 300 members including software and hardware vendors for the Industrial Automation market. In the 90s, the Foundation defined a set of standards for the interoperability of supervisory control and data acquisition (SCADA) software. These standards are known as OPC (OLE for Process Control), and specify how a distributed system for automation and process control should be developed.

OPC is based on client-server architecture. OLE refers to Object Linking and Embbedding, which is a Microsoft technology for software components. OLE became later known as COM (Component Object Model) or "ActiveX", which was followed by DCOM (Distributed COM). So the OPC standards depends specifically on DCOM technology.


Trying to improve its concept of interoperability, OPC Foundation released a new specification in 2003, not anymore depending on DCOM. This new specification, OPC XML-DA, uses SOAP (Simple Object Access Protocol) as a platform for data communication. Requests and responses are stored in XML structures, which are transmitted over HTTP.

XML (eXtensible Markup Language) is becoming widely accepted in all areas of Information Technology due to its main advantages: XML is extensible, which means it can always adapt to new technologies; and XML is platform-independent, which means that it can be used in any operating system, and with software written in virtually any language. XML is a text-based markup language, making it easy to be transmitted even through network firewalls.

The OPC XML-DA specification is implemented as Open-Source in the project OpenDA by Mark Beharrel.


MODBUS is a master/slave communication protocol present in many digital instruments as process controllers, programmable logic controllers, signal transmitters and dataloggers. It was originally written for the Modicon Controllers. MODBUS is a very popular protocol nowadays, so OSMOX should find immediate application in Industries and Laboratories. The specification for the MODBUS protocol is freely available at www.modbus.org.

about this project

OSMOX began in Universidade Federal de Santa Catarina as a project for the course in Automatics & Control Engineering, and is supported by Fundação CERTI's CMIP (Center for Metrology and Inovation in Processes). Visit the OSMOX site at SourceForge to know more about its development. For further information, please mail the author.

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