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Embedded Web app server development (Part 2)

Posted: 28 Mar 2014 ?? ?Print Version ?Bookmark and Share

Keywords:Web application? LAN? TCP/IP? Embedded systems? ruggedized PC?

From the user's perspective, the client browser continues seamlessly without any apparent 'freezing'. The presentation of the remainder of the form continues seamlessly and the real time data signal strength data appears when it becomes available.

The XMLHTTPRequest API is weird and cumbersome, but luckily many JavaScript libraries such as the jQuery library makes it very easy to use this object. jQuery is ideally suited since it is small and makes it easy to write compact JavaScript code without having to learn the details of the browser's Document Object Model, as illustrated by code Example 3.

Code Example 3: Using Ajax to respond to the satellite dish client application request for a signal strength update.

Example 3 Script code comments.

Embedded web apps: a different environment
The underlying HTTP communication technology for Web-based applications is the same, whether embedded or otherwise. But the difference in environment for the embedded sector makes a massive difference to the optimal deployment of that technology.

In this environment, you want developers to spend their time on application-specific code whether it controls tunnel lights or a satellite dish or drives safety-critical applications like a tank turret or incubator, where speed and efficiency are vital.

Using an application server specifically designed for embedded web applications ensures that generic HTTP communications are tackled with approaches which are optimised for the demands of limited resource, deeply embedded applications.

When used in conjunction with Lua Server Pages and AJX/JSON asynchronous data handling, the developer gains three technologies that combine to powerfully create the same quality of dynamic application they've come to expect from advanced smart phone and desktop applications.

With these tools, teams can focus on application development that gives users the interface they want, while letting the team dedicate most of its energy to the applications only they do best.

Embedded web apps the easy way
To be used in combination with this two part series, we have created four online tutorials you can download using browsers running on Windows XP, Vista, and Windows 7 & 8. They will give you the fundamentals for writing your own web applications and interfacing these applications to your hardware. It's not technical to run; just download and run the executable. After unpacking, a black console window will open with some instructions. The demo will open your browser automatically after 30 seconds if you do not do anything.

After downloading the self-extracting zip file, start the self-extracting zip file and follow the self extracting zip wizard. Unzip to any directory. The self extracting zip file should automatically start the unpacked 'startdemo.bat' batch script, which in turn starts the demo server in a command window. Closing this window closes the server. You can restart the demo at any time by restarting the 'startdemo.bat' batch script. Uninstall by deleting all files unpacked by the self extracting zip file.

About the author
Wilfred Nilsen, Founder & CTO of Real Time Logic, has 25 years' experience in designing embedded software. Powered by a vision of a connected embedded systems, he designed the Barracuda Application Server, tailoring it for the small footprint, real-time needs of embedded microcontrollers and microprocessors.

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