As we have seen earlier in our articles - Profibus protocol – Communication Profiles and Physical Layers, A Comprehensive Guide to Profibus Fieldbus Data Link Layer, A Guide to Profibus Application A Guide to Profibus Application Profiles, Profibus is a complex standard. With a plethora of OEM’s manufacturing master and slave devices, there is a need to define mechanisms to enable device integration in the field easy and faster. Though the Profibus application profiles are based on Function Blocks and Application blocks, still the combinations and custom features are far too much to handle in simple ways. For this purpose, Profibus International and the industry have evolved a few ways to specify and capture the device specifications and leverage them in the control devices. This article will outline the various file formats and components that are utilized in the Profibus device integration process.
Profibus GSD files
At the first level of device specification lies the Profibus General Station Description file, more commonly called the GSD file. It is a human readable ASCII text file that contains numerous keywords describing the device's characteristics. This GSD file contains the vendor and device identification information, configuration, parameters, modules, diagnostic and alarms etc. The GSD file contains the following sections.
General Specifications: Contains common communication and device information such as Vendor/Device names, Hardware, and Software revisions, supported transmission rates, time intervals etc. Master Specifications: Parameters specific to master implementation such as the maximum number of slave devices that can be connected etc. Typically, GSD files of all connected devices are compiled together to form the master parameter record. The master parameter record contains all the slave parameters and configuration data along with address allocation list, the bus parameters for all the connected slaves. This is to configure the communication with each of the slaves before going to the data exchange phase.
Slave Specifications: Specific to slaves, this section contains information such as the number and type of I/O channels, specification of diagnostic text, support for auto-baud and information on available modules with modular devices.
A Profibus GSD file is typically named by combining the vendors's name with the device identification number. For the ABB's 082D PROFIBUS DP adapter module, “abb_082d.gsd” is used. To support different languages, the GSD files are available in different extensions -. gsd for German, .gss - Spanish, .gsf - French, .gse - English etc.
Profibus EDD files
While the Profibus GSD file can describe the device's features, it is in many cases not enough to describe the application-level uses of the device. For example, while it may convey the functional blocks inside a transmitter, it will not be able to describe the unit of measurement, default value etc. This brings in a need for a more elaborate description language that can describe the Data (such as device parameters and their dependencies), Communication (e.g. Addressing Information), User Interfaces (graphical representations, graphing system) and Operations (e.g. simulation mode, Calibration). The Electronic Device Description Language (EDDL) comes handy for this purpose. EDDL is standardized as IEC 61804-2 and describes the format of EDD file. The EDD is text-based description of the device characteristics such as its instrumentation and equipment parameters in an OS and HMI agnostic manner.
Being an open technology, the EDD also finds wide application in other major field bus protocols like FOUNDATION, HART apart of Profibus. With a combination of GSD and EDD it will be possible to fully capture the features of the Profibus device at all levels.
FTD/DTM Technology
GSD files and EDD files are text-based information that can be consumed by a tool from any vendor and processed. While it is sufficient for most cases, visualization of the configuration is a challenge. The next level of integration comes with the FDT/DTM technology, an open framework independent of specific host system, where the device configuration is available as a UI component that can be directly consumed by a master configuration tool as a plug-in. A frame application, called the Field Device Tool (FDT), that could be a standalone application or embedded inside a control system, renders a graphical user interface. The Device Type Manager (DTM)are software components that are essentially device drivers for the field devices managing their device descriptions, electronic device descriptions, and field device integration device packages. Each of the field devices has their DTM developed by the vendors and can be plugged in seamlessly on to the FDT tool.
Profibus Device Integration
While the original specification of FDT implemented DTM as a Windows ActiveX control, the FDT Group has recently defined the FDT Unified Environment (UE), also known as FDT 3.0, enabling a platform independent and data-centric integration solution using HTML5/JS technology.
Profibus Diagnostics
One unique advantage with the Profibus protocol is that it has inherent support for network diagnostics. In a Profibus network, the physical level care must be taken to ensure terminations are properly done without missing them or over doing them so that the signal strengths are not degraded. Sometimes the length of the network segment may have exceeded the capacity. Similarly, if the number of devices is more than the driving capacity in a segment, the quality will be affected. Bus and protocol analyzers can be used to monitor the quality of the communication channel.
Parameters such as baud rate, network address, and data format need to be carefully configured to ensure seamless communication between devices. Additionally, the configuration stage allows for the assignment of device-specific parameters, such as sensor ranges or actuator control parameters. Proper configuration is essential to ensure compatibility, avoid conflicts, and optimize the performance of the Profibus network.
Profibus defines alarms that can be used to convey the status of the process variables, or the control devices connected on the network. The usability of the process variable can also be sent over status information for the consumer to decide whether to make use of it or not. Powerful diagnostics tools and availability of rich visualization in modern HMIs are readily available. By leveraging these, engineers can quickly identify the root causes of network issues and take appropriate corrective actions.
Tools and Software for Profibus Management
Being one of the most adopted industrial automation protocols, there are various tools and software available for Profibus device integration.
Profibus International (PI) offers tools like PROFIdrive Profile Tester, PROFIBUS GSD Editor, FDI Tools & Components, EDD Import Library, IODD Viewer etc. There are numerous Profibus Master simulators available from vendors like Bihl-Wiedemann, AnyBus, Pepperl-Fuchs, Deutschmann etc. Profibus protocol analyzers are available from Procentec, Indu-Sol, Autem, Softing, Datatec etc.
On top of these there are many FDT/DTM tools that can be used for UI based device management. With this abundant set of tools and software, it is quite easy to deploy and manage Profibus network of any complexity.
These monitoring and troubleshooting tools and software offer real-time insights into the network's health, enabling proactive maintenance and minimizing downtime.
Profibus Device Certification
To ensure interoperability and compatibility between different devices in a Profibus network, device certification plays a crucial role. Profibus International (PI), the organization responsible for the Profibus standard, provides a certification process for device manufacturers.
Device certification ensures that devices meet the required standards and specifications defined by Profibus International. Certified devices undergo rigorous testing to ensure proper functionality, performance, and compliance with the Profibus standard. By choosing certified devices, users can be confident about the compatibility and reliability of the devices in their Profibus network.
Conclusion
In conclusion, apart from rich support for Profibus device integration, it also offers a wide range of capabilities for the field devices to enhance the functionality and performance of industrial automation systems. From safety solutions to precise control and efficient diagnostics, Profibus provides engineers with the tools they need to optimize their automation systems.
By understanding and utilizing the device integration tools and techniques engineers can harness the power of Profibus and unlock new possibilities in their industrial automation system to take it to the next level of performance, efficiency, and reliability.
