Internet connectivity: The time is right and the technology is ready for you
By Olaf Pfeiffer and John Rodrigues
[ Introduction
| Internet Connectivity Parameters | Case
Study ]
[ Adapting the Software | Dynamic
Web Pages | Feedback with Forms
]
[ Continuous Refresh | Security
| Summary ]
| < Previous Page |
Adapting the Software
Once the hardware components and development tools were in place, implementation was straightforward. Using #define statements, the source code was configured to enable/disable certain protocols and features. We enabled modem and PPP support, as the serial channel of the 8051 was connected to an external modem and we wanted to allow users to dial-up the system. Furthermore we selected TCP (vs. UDP) as the main transport protocol and enabled the HTTP Web server.
After making the local adjustments to the timers (required to select a baud rate and to implement a timeout based on multiples of milliseconds) and assigning some fixed IP addresses to both the local server and the dial-up host, we quickly finished the microcontroller specific adaptations.
Before activating the Web server, we needed to have some Web pages in place. Fortunately, they can be written in standard HTML. We used a conversion utility to convert any DOS/Windows file (no matter if HTML, GIF or other) into a pair of .h and .c files. These were directly included into the project and easily added to the minimized virtual file system implemented within the TCP/IP software stack.
We were then ready for the first test: Our computer's internal modem was connected via a telephone line to the external modem that was connected to the serial port of the 8051. Using an in-circuit emulator we loaded the code to the application and hit "GO." On the computer side we had to specify a new dial-up connection using the fixed, assigned IP number we specified earlier in the code.
Using the login name and password specified in the code, we had a successful dial-up. We started the Web browser and in the URL field we typed in the IP address of the 8051 board. As this is a closed system with no domain name server, the 32-bit IPv4 addresses have to be used to directly identify the connected computers.
Our two Web pages were displayed as static files with a small graphic served by an 8051 running at 12 MHz.
However, the excitement cooled off pretty quickly. We were only serving up plain, static Web pages with no application specific data. So, the next step was to implement Web pages that are dynamically updated by the server and display data from the application.
| < Previous Page |
[ Introduction
| Internet Connectivity Parameters | Case
Study ]
[ Adapting the Software | Dynamic
Web Pages | Feedback with Forms
]
[ Continuous Refresh | Security
| Summary ]
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