embedded world

8/8/2019 Embedded World

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Using Embedded Web-servers in Industrial ApplicationsDipl.-Ing. Peter Brügger,

iniNet Solutions GmbH, Seewenweg 5, 4153 Reinach, Switzerland,Chairman VPI Initiative, [email protected]

Fon:+41617169626 Fax: +41617169617

Prof. Dr.-Ing. Axel Sikora Steinbeis-Transfer Centre Embedded Design and Networking, University of Cooperative Education Loerrach, Germany, Member of the Board VPI Initiative,

[email protected]

1 Abstract

This presentation is intended to focus on the typical concerns of a company whendeciding whether or not to use Ethernet and Web-Technology in a new design. It issplitted into the following sections:- What is the reason for using Embedded Internet? Embedded Internet allows a

dramatic cost reduction as well in the development phase as over the lifetime of

the product.- How to achieve this cost reduction? The consequent integration on the HTTP

protocol and the use of existing SW and HW building blocks allows the focus onthe company’s core competence.

- How important is security? Security is crucial when connecting to the Internet.However, the internet connection is generally only one aspect of embeddedInternet. The VPI-Initiative (Virtual Private Infrastructure) offers an open, secure,and scalable approach using standard protocols.

- What about real life examples? The last section shows existing products (in massproduction) which have successfully implemented these concepts.

2 Why Using Embedded Internet

There are a lot of questions about the motivation of using web-technologies inembedded devices [4]. The most important of them is, whether web-technology isable to solve a demand which could not be solved before using another technology.We believe that this is not the case. All demands for an embedded system can besolved with other technologies, too. The real reason for the use of Web-technologieslies in the potential of cost savings over the lifetime of a product.

2.1 The Problems of Legacy Architecture

Many existing products are based on a software-design which was defined five or

even ten years ago. Over the time, additional requirements had to be added to keepthe product up to date. Very often, additional interfaces and protocols had to beadded, making the overall software-architecture more and more difficult to maintain.The following issues are concerned:- product development and maintenance- production and integration- flexibility for changes on the existing productEthernet, TCP/IP and especially HTTP are the first protocol to integrate all demandsfor external interfacing of an embedded product. External interfacing can include- local MMI’s- remote MMI’s- interface to SCADA

- interface towards third party products- interface for database connectivity



- remote maintenance- parameter and calibration interface for production and product integration- interface for quality controlWith a traditional approach, the embedded system had to be extended with newfeatures and new protocols to follow up the demands. The system became more andmore complex, resulting in ever growing engineering and maintenance cost.However, the most crucial benefit with embedded web-servers and its underlyingprotocols is the seamless integration into the standard (office-driven) IT world. Theycan even be compatible with Microsofts .net products.

3 Focus on Core Competence

Consequent integration of all demands resulting from external interfacing on theHTTP protocol proved to reduce the overall system cost in many industrial products.One of the reasons why many developers still hesitate to use TCP/IP lies in thecomplexity of this protocol. It seems easier to add e.g. another feature on a serialfieldbus protocol than to make the big step towards Ethernet. The main task of the

developer mostly lies in the field of real-time and control issues, and not in the areaof standard IT protocols.

3.1 Webserver enabled systems

This contradiction can be solved by using existing Software- and Hardware buildingblocks. As an example, the goNet evaluation Kit [1] will be presented. This kitintegrates a HW design consisting of a microcontroller, an Ethernet interface and allthe necessary software (RTOS, TCP/IP, web-server, connectivity) already included.Using an approach based on existing embedded building blocks allows a highefficiency in software development. The engineer can focus on the core competencein the area of control, measurement and automation.

The image above shows a block diagram of the software components that are

integrated on the embedded system based on a 32 Bit Microcontroller (V850/NEC).



The goal is to speed up the development time and thus to reduce time to market, aswell as lowering the cost and the risk of a design failure. To achieve this, it takesmore than adding several software components on a microcontroller:- A hardware reference design integrating all necessary components. The

schematics of the reference design can be used by the customer. They can beextended with additional, product specific circuits.

- The development of the software can be started at the same time on an existingevaluation board. When the customer-specific hardware is ready, the softwarecan be ported easily from the evaluation-board to the new hardware.

- A JTAG debugger can be plugged in to the customers hardware. The time to testand set up the hardware is very short, because the core components have allbeen reused from the reference design, both for hardware and software. After afew days, the developer can focus on the control software and the additionalcircuitry.

The design should be based on an industry proven microcontroller family rather thanon a specific single chip solution (Ethernet controller + Microcontroller) for several

reasons:- A large, scalable family of microcontrollers offers the flexibility to develop aproduct range to address several tasks. For every task, the microcontroller whichfits best in terms of integrated functions can be chosen. The software andhardware architecture can remain almost identical.

- Long term availability: Standard microcontrollers are in production for a longerperiod of time. They are designed for the specific needs of industrial applications.When they go out of production, an upward compatible solution is offered veryoften.

3.2 Network Oriented Software

An embedded system integrating TCP/IP has two jobs to do. First, it has to controland measure. In these terms, the system has the same tasks as ten or twenty yearsago. Second, the TCP/IP interface makes the embedded controller part of adistributed system. As introduced in the beginning, these are the possibilities whichbring in the ‘Value-Add’ of the new technology. An embedded Webserver and aTCP/IP stack are just 20% of the solution. There will be many more functions that aredemanded by the network.

3.2.1 VisualisationThe embedded Webserver can be used to offer an MMI to an external Browser.These MMI’s can be used for- configuration- local operation- remote operation- remote maintenanceStandard HTML authoring tools mostly do not meet the demands of an automationapplication:- no animated visualisations- they are too complicated for users on the factory floor- the code size of the MMI’s becomes very large

The SpiderControl Editor is a pure graphic development tool for Java Applet-basedgraphic interfaces. It offers the user the option of a convenient development of MMIs.



The Editor is tailored to the needs of automation and provides compact and, aboveall, extremely portable solutions which can be stored directly on an embeddedSystem.

The whole development cycle for set-up and integration of a user interface can berealised in a few simple steps with such a tool. The user does not need to cope withJava code, browser incompatibilities and webserver programming, but is left toconcentrate solely on the functionality of the surface

3.2.2 Embedded VisualisationThe MMI’s produced with the above editor can be executed in any Java-enabledWeb-Browser. But in the same time, the MMI’s which are designed with this tool canbe used on an embedded system integrating a LCD-touchscreen, e.g. 1/4VGA. Thistechnology is called microbrowser. The microbrowser implements the samevisualisation objects that exist as a Java implementation, but written in the C-language. It is therefore possible to run sophisticated, webserver based MMI’s on asmall 16Bit Microcontroller.

3.2.3 SOAP InterfaceSOAP is facing a growing importance as a truly portable RPC (Remote ProcedureCall) standard also in the embedded world. On an embedded system, it is possible toimplement both a SOAP server or client which is fully compatible to the office IT-world and the Internet. Gateways, drivers or even OPC are no more necessary.



4 Internet Security

4.1 Parameters

As presented above, connectivity to the internet is only one aspect of embedded

Ethernet. Obviously, security is an absolutely crucial issue. The following problemsarise:- How can the embedded system be presented to the internet without damaging

firewall security concepts?- How can embedded web-servers be maintained by people from the factory floor,

who do not have the know-how to manage complex VPN connections andfirewalls?

- The owner of the embedded system, the machine or the factory does not want toloose control over his equipment. Access rights must be under tight control by theowner. Connections can be opened on demand, only by the owner, also byuntrained people.

- Devices must be attached to the internet using different communication

technologies (PSTN, ISDN, ADSL, or GSM modems, Leased Lines,...). All ofthese possibilities must be seamlessly integrated and maintained.

4.2 VPI-Initiative

The VPI-Initiative [2] has defined some basic standards to solve these issues. Theideas are based on the integration on the HTTP protocol. It includes Internet portals,HTTP relaying- and tunnelling mechanisms to fulfil the above demands.



A VPI portal needs to fulfill three important requirements:- Security has to be conveyed in a plausible and comprehensible manner- The connection between portal and embedded system has to be fully

interchangeable- If there are leased lines they have to be used with a minimal expenses- The portal may has to be used transparently by both automatic processes as well

as real users.

The prerequisites of an embedded system are as follows:- Integration of an HTTP server which makes available the user surfaces specific to

the machines- The HTTP server has to allocate an interface for remote procedure calls for

access to its variables and functions.

HTTP Tunneling A VPI-agent allows to reach a device via the Internet even if it is behind a firewall anddoes not have a “public” TCP/IP number.

The operator of the intranet has control over the VPI-agent and can define at anytime which target systems should be imaged on the Internet. Through the InternetService Provider (ISP) the VPI-agent keeps a tunnel to a central webserver on theInternet (or VPI-portal). A user now selects the address of this server and mustidentify himself with his user name and password. Subsequently, this user receives alist with the links (direct on the target system) to which he has right of access. If theuser selects such a target, the connection is now taken up fully transparent andmaintained via the marked route.The VPI-agent is a software module which can be operated on any system within theintranet. A PC, a server or a suitably embedded device can be used for this.

5 Examples

5.1 Introduction

In this section, some design examples will be discussed not only in terms ofarchitectural issues, but also to demonstrate the broad range of applications withcommercial benefit from embedded internet.

5.2 Building Automation

The ‘Ambus-Net’ device is used in the metering/building automation sector. It iscapable of maintaining up to 255 meters (cold-/warm-water, electricity, flow,…)attached to the M-Bus. Features:- 16 Bit@20MHz micro-controller- Local touchscreen/MicroBrowser- Embedded Webserver MMI’s- Alarming over networks- Modem/ISDN/GSM connectivity for remote maintenance- Compact-Flash media data logging- SOAP InterfaceThe Ambus-Net is a true microcontroller design. By the intense use of existingbuilding blocks, the system was developed in very short time at very moderatedevelopment costs.



Ambus-Net can be attached to a VPI-Portal via the integrated Modems (all options)or via Ethernet and a VPI-Agent.

5.3 Measure and Control (MSR)The following example (Kistler Instruments) describes a modular, Web-server basedpressure measuring device implementing very demanding real-time computing tasks.The Web-server is used for most of the tasks for external interfacing describedearlier. Features:- 32 Bit@40MHz micro-controller- Remote configuration with Internet Explorer or external MicroBrowser device- Various data processing services for database storage, quality control, backup,

file exchange, etc. using the webserver interface

5.4 Automation

SAIA-Burgess is a well known manufacturer of PLC’s. Most of their PLC’s integrate awebserver which can also be used for viualisation. The programming tool has anintegrated MMI Editor which allows to create MMI’s for Java-enabled Browsers oreven lean MicroBrowser clients. Due to their open and extendible webserverarchitecture, these products have become a very attractive choice for web-basedprojects in building- as well as machinery and factory automation. SAIA-Burgessclaims that the approach of distributed control using Web-technology marks a changeof paradigm and often allows to avoid the presence of a PC or IPC in many projects,thus becoming both a more reliable and cheaper solution.



6 Sources

[1] http://www.unique-aktuell.de/hotspot/2003/hs_12/hs_12.htm[2] http://www.vpi-initiative.com[3] Sikora, A., Brügger, P., "Virtual Private Infrastructure - An Industry Consortium

for Unified and Secure Web Control with Embedded Devices", 9th IEEEInternational Conference on Emerging Technologies and Factory Automation

(ETFA 2003), Lisbon, Portugal, 16-19 September 2003.[4] Sikora, A., "Embedded Applikationen im Internet", Teil 1: "Übersicht über Vor-und Nachteile von vernetzten Anwendungen", Elektronik 22/2000, S.90 - 102,Teil 2: "Implementierungen", Elektronik 23/2000, S.164 - 169.

[5] http://www.spidercontrol.net

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