Designing a telemetric system based on an embedded webserver

OData support
Csordás Péter
Department of Measurement and Information Systems


The aim of this thesis is to develop a remote monitoring and alarm system that may be used in versatile applications, which is universally configurable for many cases. The device is easily accessible remotely from the internet using a modern web browser, or through a GSM network using the GSM modem connected to the device. By means of this interface, the system can also send alarm messages for many predefined events.

The device has multiple analog and digital inputs in order to measure physical quantities (e.g. temperatures, pressures) and two-state sensors (eg. switches, reed-relays). It has two kinds of outputs: low-voltage open-collector digital outputs and potential free, high voltage outputs in order to be able to interact with the environment.

The device is based on an STM32F107, Cortex-M3 architecture microcontroller from the STMicroelectronics. It is optimal because it is a connectivity-line micro with integrated MAC peripheral. The Ethernet physical layer is provided externally with Ethernet-PHY ASIC. On software side, the FreeRTOS operating system runs on the microcontroller. A webserver task is responsible for handling HTTP queries from Ethernet interface with authentication. The Ethernet communication layer is implemented by lwIP, an open-source TCP/IP stack. The device has a high-capacity memory card connected using FAT file system. This memory card can be accessed by the webserver task, thus it provides the content for the web interface. The handling of FAT file system is done by FatFS, an external open-source library. A graphical user-interface over the web site is provided by a Java Applet application running in the browser. This Java Applet is also stored on the memory card.

An own JTAG adapter has been also developed in order to support the development processes.

The device schematics and hardware layout as well as the software modules with source codes are available in the appendix.


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