OPC UA开源实现open62541技术文档详解

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"OPC UA开源实现open62541技术文档" OPC UA（OPC统一架构）是一种工业通信标准，旨在提供跨平台、安全、可靠的数据交换。open62541是用于实现OPC UA规范的开源库，支持创建OPC UA服务器和客户端。这份文档详细介绍了open62541的功能、构建过程、安装方法以及一系列教程，帮助开发者深入理解和应用该技术。 1. OPC Unified Architecture OPC UA不仅仅是一个通信协议，它是一个完整的信息模型，包括数据类型、服务集和安全框架。它旨在统一各种设备和系统的通信，支持数据的透明访问，并确保数据的安全传输。OPC UA提供了一种标准化的方式来访问、组织和交换工业自动化环境中的数据。 2. open62541 Features open62541库实现了OPC UA规范的全部功能，包括： - 完整的服务器和客户端堆栈 - 安全通信，支持多种安全策略和加密算法 - 自定义数据类型、对象和方法的创建 - 支持发布/订阅通信模式 - 集成的证书管理工具 - 可配置的性能优化选项 3. Building open62541 构建open62541涉及到编译库、设置构建选项、构建示例应用以及针对特定架构的构建。文档提供了详细的步骤和参数，指导用户如何在不同平台上正确构建项目。 4. Installing open62541 安装open62541可以通过手动安装或使用预构建的软件包进行。手册中包含了手动安装的步骤，以及对于Linux、Windows和macOS等不同操作系统的预构建包的获取和使用方法。 5. Tutorials 文档提供了一系列教程，涵盖了从基础到高级的OPC UA操作： - 数据类型：介绍如何创建和使用OPC UA内置及自定义数据类型 - 简单服务器：建立一个基本的OPC UA服务器并添加变量 - 连接物理过程：将OPC UA变量与实际设备连接 - 变量类型：操作变量类型的创建和使用 - 对象和对象类型：添加和管理OPC UA对象及其类型 - 方法：在对象上添加和执行方法 - 监视属性：使用本地监控项观察属性变化 - 事件生成：创建和处理OPC UA事件 - 报警和条件服务器：集成报警和条件功能 - 简单客户端：构建一个能够与OPC UA服务器交互的客户端 - 发布/订阅：利用OPC UA的发布/订阅机制进行数据交换 6. Protocol and DataTypes 文档还涵盖了OPC UA协议的细节，如建立连接、协议消息结构，以及数据类型的部分，包括内置类型和通用类型。通过这份详尽的文档，开发者可以全面了解open62541库，掌握如何在实际项目中应用OPC UA技术，无论是构建服务器还是客户端，都能找到清晰的指导。此外，文档中还强调了寻求帮助和贡献代码的途径，鼓励社区参与和共享知识。

open62541 Documentation, Release 1.2.0-5-gcc3a3d396-dirty

UA_ENABLE_FULL_NS0 Use the full NS0 instead of a minimal Namespace 0 nodeset UA_FILE_NS0 is used

to specify the ﬁle for NS0 generation from namespace0 folder. Default value is Opc.Ua.NodeSet2.xml

2.2.4 Debug Build Options

This group contains build options mainly useful for development of the library itself.

UA_DEBUG Enable assertions and additional deﬁnitions not intended for production builds

UA_DEBUG_DUMP_PKGS Dump every package received by the server as hexdump format

2.2.5 Building a shared library

open62541 is small enough that most users will want to statically link the library into their programs. If a shared

library (.dll, .so) is required, this can be enabled in CMake with the BUILD_SHARED_LIBS option. Note that this

option modiﬁes the ua_config.h ﬁle that is also included in open62541.h for the single-ﬁle distribution.

2.2.6 Minimizing the binary size

The size of the generated binary can be reduced considerably by adjusting the build conﬁguration. With open2541,

it is possible to conﬁgure minimal servers that require less than 100kB of RAM and ROM.

The following options inﬂuence the ROM requirements:

First, in CMake, the build type can be set to CMAKE_BUILD_TYPE=MinSizeRel. This sets the compiler ﬂags

to minimize the binary size. The build type also strips out debug information. Second, the binary size can be

reduced by removing features via the build-ﬂags described above.

Second, setting UA_NAMESPACE_ZERO to MINIMAL reduces the size of the builtin information model. Setting

this option can reduce the binary size by half in some cases.

Third, some features might not be needed and can be disabled to reduce the binary footprint. Examples for this

are Subscriptions or encrypted communication.

Last, logging messages take up a lot of space in the binary and might not be needed in embedded scenar-

ios. Setting UA_LOGLEVEL to a value above 600 (FATAL) disables all logging. In addition, the feature-ﬂags

UA_ENABLE_TYPEDESCRIPTION and UA_ENABLE_STATUSCODE_DESCRIPTIONS add static informa-

tion to the binary that is only used for human-readable logging and debugging.

The RAM requirements of a server are mostly due to the following settings:

• The size of the information model

• The number of connected clients

• The conﬁgured maximum message size that is preallocated

2.3 Building the Examples

Make sure that you can build the shared library as explained in the previous steps. Even easier way to build the

examples is to install open62541 in your operating system (see Installing open62541).

Then the compiler should automatically ﬁnd the includes and the shared library.

cp /path-to/examples/tutorial_server_firststeps.c . # copy the example server

gcc -std=c99 -o server tutorial_server_firststeps.c -lopen62541

10 Chapter 2. Building open62541

open62541 Documentation, Release 1.2.0-5-gcc3a3d396-dirty

2.4 Building for speciﬁc architectures

The open62541 library can be build for many operating systems and embedded systems. This document shows a

small excerpt of already tested architectures. Since the stack is only using the C99 standard, there are many more

supported architectures.

A full list of implemented architecture support can be found in the arch folder.

2.4.1 Windows, Linux, MacOS

These architectures are supported by default and are automatically chosen by CMake.

Have a look into the previous sections on how to do that.

2.4.2 freeRTOS + LwIP

Credits to @cabralfortiss

This documentation is based on the discussion of the PR https://github.com/open62541/open62541/pull/2511. If

you have any doubts, please ﬁrst check the discussion there.

This documentation assumes that you have a basic example using LwIP and freeRTOS that works ﬁne, and you

only want to add an OPC UA task to it.

There are two main ways to build open62541 for freeRTOS + LwIP:

• Select the cross compiler in CMake, set the ﬂags needed for compilation (different for each microcontroller

so it can be difﬁcult) and then run make in the folder and the library should be generated. This method can

be hard to do because you need to specify the include ﬁles and some other conﬁgurations.

• Generate the open6254.h and open6254.c ﬁles with the freeRTOSLWIP architecture and then put these ﬁles

in your project in your IDE that you’re using for compiling. This is the easiest way of doing it and the

documentation only focus on this method.

In CMake, select freertosLWIP using the variable UA_ARCHITECTURE, enable amalgamation using the

UA_ENABLE_AMALGAMATION variable and just select the native compilers. Then try to compile as always.

The compilation will fail, but the open62541.h and open62541.c will be generated.

NOTE: If you are using the memory allocation functions from freeRTOS (pvPortMalloc and family) you will need

also to set the variable UA_ARCH_FREERTOS_USE_OWN_MEMORY_FUNCTIONS to true. Many users had

to implement pvPortCalloc and pvPortRealloc.

If using the terminal, the command should look like this

mkdir build_freeRTOS

cd build_freeRTOS

cmake -DUA_ARCHITECTURE=freertosLWIP -DUA_ENABLE_AMALGAMATION=ON ../

make

Remember, the compilation will fail. That’s not a problem, because you need only the generated ﬁles

(open62541.h and open62541.c) found in the directory where you tried to compile. Import these in your IDE

that you’re using. There is no standard way of doing the following across all IDEs, but you need to do the follow-

ing conﬁgurations in your project:

• Add the open62541.c ﬁle for compilation

• Add the variable UA_ARCHITECTURE_FREERTOSLWIP to the compilation

• Make sure that the open62541.h is in a folder which is included in the compilation.

When compiling LwIP you need a ﬁle called lwipopts.h. In this ﬁle, you put all the conﬁguration variables. You

need to make sure that you have the following conﬁgurations there:

2.4. Building for speciﬁc architectures 11

open62541 Documentation, Release 1.2.0-5-gcc3a3d396-dirty

#define LWIP_COMPAT_SOCKETS 0 // Don't do name define-transformation in networking

˓→function names.

#define LWIP_SOCKET 1 // Enable Socket API (normally already set)

#define LWIP_DNS 1 // enable the lwip_getaddrinfo function, struct addrinfo and

˓→more.

#define SO_REUSE 1 // Allows to set the socket as reusable

#define LWIP_TIMEVAL_PRIVATE 0 // This is optional. Set this flag if you get a

˓→compilation error about redefinition of struct timeval

For freeRTOS there’s a similar ﬁle called FreeRTOSConﬁg.h. Usually, you should have an example project with

this ﬁle. The only two variables that are recommended to check are:

#define configCHECK_FOR_STACK_OVERFLOW 1

#define configUSE_MALLOC_FAILED_HOOK 1

Most problems when running the OPC UA server in freeRTOS + LwIP come from the fact that is usually deployed

in embedded systems with a limited amount of memory, so these deﬁnitions will allow checking if there was a

memory problem (will save a lot of effort looking for hidden problems).

Now, you need to add the task that will start the OPC UA server.

static void opcua_thread(void

arg){

//The default 64KB of memory for sending and receicing buffer caused

˓→problems to many users. With the code below, they are reduced to ~16KB

UA_UInt32 sendBufferSize = 16000; //64 KB was too much for my

˓→platform

UA_UInt32 recvBufferSize = 16000; //64 KB was too much for my

˓→platform

UA_UInt16 portNumber = 4840;

UA_Server

mUaServer = UA_Server_new();

UA_ServerConfig

uaServerConfig = UA_Server_getConfig(mUaServer);

UA_ServerConfig_setMinimal(uaServerConfig, portNumber, 0, sendBufferSize,

˓→recvBufferSize);

//VERY IMPORTANT: Set the hostname with your IP before starting the server

UA_ServerConfig_setCustomHostname(uaServerConfig, UA_STRING("192.168.0.102

˓→"));

//The rest is the same as the example

UA_Boolean running = true;

// add a variable node to the adresspace

UA_VariableAttributes attr = UA_VariableAttributes_default;

UA_Int32 myInteger = 42;

UA_Variant_setScalarCopy(&attr.value, &myInteger, &UA_TYPES[UA_TYPES_

˓→INT32]);

attr.description = UA_LOCALIZEDTEXT_ALLOC("en-US","the answer");

attr.displayName = UA_LOCALIZEDTEXT_ALLOC("en-US","the answer");

UA_NodeId myIntegerNodeId = UA_NODEID_STRING_ALLOC(1, "the.answer");

UA_QualifiedName myIntegerName = UA_QUALIFIEDNAME_ALLOC(1, "the answer");

UA_NodeId parentNodeId = UA_NODEID_NUMERIC(0, UA_NS0ID_OBJECTSFOLDER);

UA_NodeId parentReferenceNodeId = UA_NODEID_NUMERIC(0, UA_NS0ID_ORGANIZES);

UA_Server_addVariableNode(mUaServer, myIntegerNodeId, parentNodeId,

˓→parentReferenceNodeId, myIntegerName,

UA_NODEID_NULL,

˓→attr, NULL, NULL);

allocations on the heap need to be freed

(continues on next page)

12 Chapter 2. Building open62541

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