Application for Communication

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1 Application for Communication OPC Communication via the SEND/RECEIVE Protocol with a Visual Basic.NET OPC Client Introduction

2 Warranty, Liability and Support Warranty, Liability and Support We accept no liability for information contained in this document. Any claims against us - based on whatever legal reason - resulting from the use of the examples, information, programs, engineering and performance data etc., described in this document shall be excluded. Such an exclusion shall not apply in the case of mandatory liability, e.g. under the German Product Liability Act ( Produkthaftungsgesetz ), in case of intent, gross negligence, or injury of life, body or health, guarantee for the quality of a product, fraudulent concealment of a deficiency or breach of a condition which goes to the root of the contract ( wesentliche Vertragspflichten ). However, claims arising from a breach of a condition which goes to the root of the contract shall be limited to the foreseeable damage which is intrinsic to the contract, unless caused by intent or gross negligence or based on mandatory liability for injury of life, body or health. The above provisions do not imply a change in the burden of proof to your detriment. The Application Examples are not binding and do not claim to be complete regarding the circuits shown, equipping and any eventuality. They do not represent customer-specific solutions. They are only intended to provide support for typical applications. You are responsible for ensuring that the described products are used correctly. These Application Examples do not relieve you of the responsibility in safely and professionally using, installing, operating and servicing equipment. By using this application example you accept that Siemens is not liable for any damages except for those specified in the above liability clause. We reserve the right to make changes to these Application Examples at any time without prior notice. If there are any deviations between the recommendations provided in this application example and other Siemens publications e.g. Catalogs the contents of the other documents have priority. Copyright 2005 Siemens A&D. It is not permissible to transfer or copy these Application Examples or excerpts of them without first having prior authorization from Siemens A&D in writing. For questions about this document please use the following address: mailto:csweb@ad.siemens.de V /23

3 Foreword Foreword Objectives of the application This example application discusses the application of the SEND/RECEIVE protocol with the SIMATIC NET OPC server. The OPC server communicates with the controller via the block and variable services of the SEND/RECEIVE protocol. It demonstrates how an OPC client, which is tailored to individual requirements, is programmed in the programming language Visual Basic.NET. The configuration of the PC station for using the SIMATIC NET OPC server with the SEND/RECEIVE protocol and Industrial Ethernet is also explained. This enables transferring structured data via the OPC interface. Main contents of this application The following main points are discussed in this application: Dealing with the communication services of the SEND/RECEIVE protocol with regards to program technology: Block services (AG_SEND / AG_RECEIVE) Variable services (FETCH / WRITE) for enabling exchange of larger data volumes between PC and mixed automation systems (i.e. SIMATIC S5 and SIMATICT S7). Configuring the SEND/RECEIVE protocol when using Industrial Ethernet Generating an OPC client with graphical user interface Demonstrating the handling of the Data Access interface of the OPC server via the Custom Interface, and the integrating process into.net- Framework using the OPC DA RC-Wrapper Displaying the procedure for implementing an additional acknowledgement mechanism (additional level 7 protocol). V /23

4 Foreword Structure of the document The documentation of this application is divided into the following main parts: Introduction Extension Demonstration Additionally, the STEP7 code and the Visual Basic.NET code are available. This first document, the Introduction, is aimed at persons who just want to have a quick overview. Part Introduction Application Description and Function Principles Extension Function Principles in detail and Program Structure Demonstration Structure, Configuration and Operation of the Application Description Provides a general overview of the contents. You will learn about the components used (standard hardware and software components and the specially created software). Discusses the detailed function processes of the involved hardware and software components, the solution structures, and where sensible the concrete implementation of this application. This part is necessary if you want to learn about the interaction of the solution components, for example in order to use them as the basis for own development. This part leads you step by step through the structure, important configuration steps, commissioning and operation of the application. An additional component available is the S7 program code. Part S7 program code Visual Basic.NET Code Description The S7 program code includes the code and a user interface which may also be used for demonstration purposes. Contains the program files of the OPC client and the Visual Studio.NET project. Reference for Automation and Drives Service & Support This entry originates from the internet application portal of the A&D Service and Support. Clicking the link below directly displays the download page of this document. V /23

5 Foreword Table of Contents Table of Contents... 5 Application Description Automation Task Overview Requirements Overview of the complete solution Description of the main functionality Required hardware and software components Basic performance data Appendix and List of Further Literature Glossary Literature Bibliographic references Internet links V /23

Automation Task Application Description Content Here you will be provided with a quick overview of the automation task to be discussed as well as its solution.

6 Automation Task Application Description Content Here you will be provided with a quick overview of the automation task to be discussed as well as its solution. You will learn about the components used (standard hardware and software components and the specially created software). The basic performance data show how powerful this application is. 1 Automation Task You are provided with information on the automation task discussed in the documentation on hand. 1.1 Overview Introduction This application is meant to illustrate the transfer of larger data volumes between the heterogeneous partners: PC and automation system. Overview of the automation task The following figure gives an overview of the automation task. Figure 1-1 V /23

7 Automation Task Description of the Automation Task Pressing elements on the user interface affects the behavior of the control program on the S7 CPU. This generates information in the controller (e.g. actual values, aggregate states, etc.) which are represented on visualization elements of the user interface. On the other hand it is possible to write larger data volumes into the controller. The principle is demonstrated at an S7-CPU with the block oriented and variable oriented interface. 1.2 Requirements Requirements on the application program The application program is meant to illustrate how the SIMATIC NET OPC server can be addressed by means of programming in Visual Basic.NET in order to read or write individual variables and variable blocks. various communication methods (block-oriented, variable-oriented) can be used parallel via the SIMATIC NET OPC server. block-oriented and variable-oriented process data can be read and written. configured variables are listed and displayed via a simple graphical user interface. The intention is to only display the S7 PC direction. send in both directions. a level 7 acknowledgement mechanism can be implemented with block and variable services. Other requirements Requirements on development language and environment: using Microsoft Visual Studio.NET using the programming language Visual Basic.NET. Other requirements on the application: time measurement for block-oriented transfer. Requirements regarding connection to the process Connection to the process data via Industrial Ethernet as well as the SIMATIC NET OPC Server V6.2. Using the OPC Data Access Custom Interface V2.05 with Runtime Callable Wrapper (RCW). V /23

2 You are provided with information on the solution selected for the automation task, the components used, and the tasks of the individual components. 2.

8 2 You are provided with information on the solution selected for the automation task, the components used, and the tasks of the individual components. 2.1 Overview of the complete solution Display The following figure displays the most important components of the solution: Figure 2-1 Setup description A PG/PC is connected to an S7-300 controller via hub. A CP 1613 network card is used for this. On the controller side, there is a SIMATIC S7-300 with the CP as well as a CPU DP. V /23

Involved software components The following figure illustrates both of the involved software components ( marks the software component generated within this application): Figure 2-2 User program in

9 Involved software components The following figure illustrates both of the involved software components ( marks the software component generated within this application): Figure 2-2 User program in the PC/ PG The user program in the PC/PG provides the following elements: A very simple graphical user interface for controlling the example. The variables of the S7 program are displayed here, enabling connecting and disconnecting the server. Enabling reading and writing of some variables for the HMI (operator control and monitoring) functions via the Send / Receive variable services (FETCH / WRITE). An option for writing larger data volumes from the CPU to data structures on the PC with block-oriented SR services. Further saving of data is not the main focus here. from the PC to data blocks (DB) on the CPU (e.g. recipe data) with block-oriented SR services. For both cases a level 7 acknowledgement for flow control. User program in the S7-CPU The STEP 7 program in the S7-CPU simulates the values to be received by the PC. structures the individual variables into performant structures, which then can be mapped to the OPC items, and triggers the respective SR block calls (only necessary for block-oriented transfer). generates the necessary telegram structures for the bidirectional transfer of larger data volumes. V /23

2.2 Description of the main functionality Main focus of the application The focus of this application on the controller side is using different connections for reading and writing of process

10 2.2 Description of the main functionality Main focus of the application The focus of this application on the controller side is using different connections for reading and writing of process variables. This may be individual variables and whole data blocks. The SEND/RECEIVE protocol (S5 compatible communication) is used for this. This enables usage with heterogeneous automation systems. On the PC side, the process variables are accessed via OPC items. The service used for data exchange is defined via the OPC items. The following services can be used: Reading individual variables via the FETCH variable service Writing individual variables via the WRITE variable service Reading data blocks via the RECEIVE block service Writing data blocks via the SEND block service For this reason the user interface of the application is divided into the following main parts, which are described in the next section. Overview of the user interface Figure V /23

Description of user interface Table 2-1 No. Description 1 Connection Connecting with and disconnecting from the OPC SIMATIC NET server installed locally.

2 Variables Reading with variable services (FETCH) Writing with variable services (WRITE) Note: The job type FETCH enables direct access to objects such as

3 Block Reading with block services (RECEIVE) Writing with block services (SEND) Note: Only valid data can be entered.

11 Description of user interface Table 2-1 No. Description 1 Connection Connecting with and disconnecting from the OPC SIMATIC NET server installed locally. Setting the update rate Illustration Note: Setting the update rate is only possible before a connection with the server has been established. 2 Variables Reading with variable services (FETCH) Writing with variable services (WRITE) Note: The job type FETCH enables direct access to objects such as inputs, outputs, data blocks, memory bits and counters. The FETCH or WRITE jobs occur via an asynchronous Read or synchronous Write. 3 Block Reading with block services (RECEIVE) Writing with block services (SEND) Note: Only valid data can be entered. Both buttons ( PC S7 and S7 PC ) are deactivated for the duration of the respective operation. 4 Language selection A click on the dialog window with the right mouse-button enables selecting the languages German or English V /23

Variable service Reading and writing individual variables The user interface offers the possibility of reading and writing three variable values.

12 Variable service Reading and writing individual variables The user interface offers the possibility of reading and writing three variable values. The following applies: Each of these three variables is generated passively in one OPC group for the two different connections FETCH and WRITE. Asynchronous read or synchronous write are executed with the respective items via the Fetch and the Write button. Block services Reading and writing a data block The following points refer to the block services: Data flow PC S7 Figure 2-4 Table 2-2 No. Description 1 On the PC, a send date is entered via the user interface. It is slightly modified into an array and sent to the S7 with a message header. 2 The S7 CPU receives the data by continuously polling a variable. 3 The S7 CPU saves the received data into a DB. 4 The S7 sends an acknowledgement to the PC. 5 The PC receives the acknowledge message from the S7 by polling a variable. Note The user interface locks the PC S7 button for as long as the job is running. Note The OPC client can simultaneously transmit a FETCH or a WRITE. V /23

Data flow S7 PC Figure 2-5 Note Table 2-3 No. Description 1 In S7, the PC triggers the sending of the S7-CPU with a passive and synchronous WRITE variable.

13 Data flow S7 PC Figure 2-5 Note Table 2-3 No. Description 1 In S7, the PC triggers the sending of the S7-CPU with a passive and synchronous WRITE variable. 2 S7 generates a telegram consisting of head and user data. 3 The telegram is sent to the PC. 4 On the PC, the program waits for a variable by means of polling. As soon as the data has been received, they are extracted and displayed. 5 A receive acknowledgement is sent to the S7 via a separate connection. The user interface locks the S7 PC button for as long as the job is running. Note The OPC client can simultaneously transmit a FETCH or a WRITE. Measuring the time duration The time interval required for a data transmission including acknowledgement is always measured. This time interval is then stored to the respective variable and displayed. It is only measured for Send / Receive. An average of the time interval for the respective transmission is calculated and displayed. This enables estimating the performance. Note The first transaction is not considered as, compared with all other transmissions, it takes considerably longer and would distort the measuring result. V /23

14 Implementation Implementation of OPC clients in.net hardly differs from the implementation in C++, as the COM mechanisms must still be followed. However, the implementation of a.net user interface is clearly faster than a comparable implementation with C++. Operations on bit level, as for example during extracting of Receive variables, are much easier with C++ or C#. For this reason, a conversion library (Conv.dll) is used in this application. It provides the functions for the bit operations in C#. Error handling The most striking difference between.net and C++ is the error handling. Instead of polling HRESULT as usual, i.e.com returned values, an exception handling is realized. Advantages of error handling In connection with the automated Garbage Collection, it has the following advantages: No error will be overlooked Code can be read easier Uniform error handling within the OPC client Possible introduction of error hierarchies by means of implementing some Exception classes V /23

15 2.3 Required hardware and software components Hardware components (S7 side) Table 2-4 Component No. MLFB / Order number Note PS307 5A 1 6ES EA00-0AA0 CPU 315-2DP 1 6ES AG10-0AB0 MMC card required CP GK EX20-0XE0 Standard hub 1 Depending on product Hardware components (PC side) Table 2-5 Component No. MLFB / Order number Note Power PG 1 6ES BA21-0LB3 Incl. STEP 7 or other Industrial PC Network card CP GK1161-3AA01 Standard software components Table 2-6 Component No. MLFB / Order number Note STEP 7 V5.3 SP1 1 6ES7810-4CC07-0YA5 Already contained in Power-PG SCL V ES7811-1CC05-0YA5 SIMATIC NET IE S V6.2 (SP1) with: OPC-RCW OPC-Server Visual Studio 2003 with.net- Framework V1.1 or higher 1 6GK1716-1CB62-3AA0 OPC-RCW and OPC server are included free of charge. Contains the required.net-framework V1.1 1 Depending on product Optional, required for adaptations. V /23

16 Example files and projects The following list contains all files and projects used in this example. Table 2-7 Component Note _OPC_SR_STEP7_v10.zip The file contains the archived STEP 7 project as well as the respective S7 program _OPC_SR_CODE_v10.zip Visual Basic.NET program: OPC client (user interface) and the source code files of the user interface _OPC_SR_Introduction_ DOKU_v10_e.pdf _OPC_SR_Extension_ DOKU_v10_e.pdf _OPC_SR_Demonstration _DOKU_v10_e.pdf Application Description and Function Principles Function Principles in detail and Program Structure Structure, Configuration and Operation V /23

17 2.4 Basic performance data Hardware In the tables below, the basic performance data of the used SIMATIC hardware components and the transaction time (example values) are mentioned. The components used in this application are framed in red. SIMATIC NET CP (343-1EX20-0XE0) Table 2-8 Criterion Basic Performance Data Transaction rate 10 Mbit/s or 100 Mbit/s Interfaces 10BaseT,100BaseTX: RJ45 Performance data: S5-compatible communication (SEND/RECEIVE) Total of all simultaneously operable TCP/UDP connections: max.16 Number of user data TCP: 8 Kbytes UDP: 2 Kbytes S7 communication: Number of connections: max.16 PG/OP communication : Number of operable OP connections (acyclic services):16 Multi-protocol operation: Total of all simultaneously operable connections max.: 32 V /23

18 SIMATIC NET CP 1613 (6GK1161-3AA00) Table 2-9 Criterion Transaction times: Interfaces Performance data (mono-protocol operation): 10 Mbit/s or 100 Mbit/s Basic Performance Data 15-pole Sub-D female connector (10/100 Mbit/s) 10BaseT, 100 BaseTX RJ-45 S7 communication Number of operable connections: 160 SEND/RECEIVE Number of operable connections: 160 PG functions Number of operable connections: 1 Application software In the following table, different aspects regarding block-oriented and variable oriented communication are evaluated. Table 2-10 Criterion Block-oriented services AG_SEND / AG_RECV Variable-oriented services FETCH /WRITE Error handling Implementation workload O + Performance ++ + Data throughput ++ O Flexible access - ++ Heterogeneous communication partners (e.g. SIMATIC S5) Measured data The average transaction times from the controller to the PC and vice versa are graphically displayed in the figure below. Measuring method In the following diagrams, the average transaction time is plotted against the data volumes. In the application, this average time is determined and displayed from the start of transmission ( Connect ). It is measured in both directions on the PC. V /23

19 Note The first transaction is in the application not considered for determining and display of the average time as, compared with all other transmissions, it takes considerably longer and would distort the measuring result. Note The given measured values can have hardware and software related fluctuations (PC, network and infrastructure). Therefore, it is possible, that your results differ from the values displayed below. Average transaction times from controller to PC In Figure 2-5 the measured time interval corresponds to the points 1-4. Figure 2-6 Transfer Übertragungszeit time in Kbytes in ms S7 => PC 0 0, Data volume Datenmenge in Kbytes in kbyte V /23

20 Average transaction times from PC to controller In Figure 2-4 the measured time interval corresponds to the points 1-5. Figure 2-7 PC => S7 600 Transfer Übertragungszeit time in Kbytes in ms , Data Datenmenge volume in in Kbytes kbyte As apparent in the curve, the expected result is confirmed, as the transaction time rises almost linear with increasing data volumes. V /23

21 Appendix and List of Further Literature Glossary 3 Glossary Appendix and List of Further Literature COM DCOM Component Object Model: Software model for communication between components based on a standardized interface; DCOM Distributed Object Model: Software model for communicating beyond computer boundaries based on COM. Eventhandler An Event handler processes occurring events or Windows messages. Exception An Exception is referred to as an exceptional situation. It can be generated either by the operating system (e.g. Division by zero) or by the user program. Exception handler An Exception handler processes occurring exceptional situations. Generally a secured error behavior and/or a message to the user. HRESULT Return data type of COM objects. IDL OPC Interface Definition Language: A Microsoft standard language for definition of function and parameter interfaces. OLE for process control. A standardization for process control created for the automation sector. Maintained by the OPC - Foundation. Several interfaces with different tasks exist. OPC client A program which uses the services of an OPC server by sending requests to the server via existing OPC interfaces. OPC DA OPC Data Access interface. The interface enables monitoring and changing of process values. V /23

22 Appendix and List of Further Literature Glossary OPC server A program which provides one of the OPC interfaces and responds to requests of an OPC client. Polling RCW Term referring to (mostly cyclical) polling of certain values or states. Runtime Callable Wrapper. A wrapper which encapsulates a Custom interface for the.net Framework. The RCW enables accessing older COM ports for the.net Framework. Sink interface Using the sink interface, messages between components can be sent. The sink interface is based on COM mechanisms. Windows message The standard Microsoft Windows operating systems exchange messages to notify of events, e.g. the paint event. Wrapper The term Wrapper normally refers to a class group which encapsulates other class groups for data conversion or easier handling. It can be considered an envelope enclosing the wrapped classes, covering them from the outside. V /23

23 Appendix and List of Further Literature Literature 4 Literature 4.1 Bibliographic references This list is by no means exhaustive and only gives a selection of appropriate sources. Table 4-1 Topic Title /1/ STEP7 Automatisieren mit STEP7 in AWL und SCL (Automating with STEP7 in STL and SCL) Hans Berger published by: Publicis MCD Verlag ISBN /2/.NET Inside C#, Tom Archer.NET Crashkurs, Clemens Vasters, Oellers, Javidi, Jung, Freiberger, DePetrillo Microsoft.NET Framework Programming, Jeffrey Richter /3/ Manual for industrial communication on PG/PC with SIMATIC NET. SIMATIC NET Industrial Communication with PG/PC Volume 1 Basics Volume 2 Interfaces Installed by SIMATIC NET, see: Start SIMATIC Documentation English in the Product Support under the entry-id: Internet links This list is by no means exhaustive and only gives a selection of appropriate sources. Topic \1\ Reference to the documentation Title \2\ Siemens A&D Customer Support \3\ OPC OPC DA 2.05a specification at V /23

Application for Communication

Application for Communication OPC Communication via the SEND/RECEIVE Protocol with a Visual Basic.NET OPC Client Demonstration Warranty, Liability and Support OPC with SEND/RECEIVE Protocol, Entry-ID: