Wireless Door-Guard System Design

It is acknowledged that it is an information age when technologies change and develop quickly today. Lots of insecure aspects such as robbery and theft grow with the development of high-tech. As a result, aptitude door-guard systems appear. However, current aptitude door-guard systems are generally based on wire communication. This is unpractical sometimes because its relative expense is high, wires are difficult to be placed, system update is hard. On the other hand, radio communication gets rid of most above demerits. This is why wireless door-guard system is a trend in the future.In this thesis, we propose a solution for wireless door-guard system. According to research on door-guard system, we figure out a software and hardware solution specially applying to residence cells. The solution bases on Master-Slaver Mode, using Radio Frequency as wireless communication method. It applies to steady data and voice transmission during multi-clients, using 868/915MHz as a carrier wave, FSK as a modulating mode and frequency division multiple access (FDMA) as an access fashion. The solution is based on single star network architecture, choosing RF module IA4420 as the core module of tranceiver circuit, it also brings in a voice codec platform as voice proceeser. In its software design, it assigns every client with a pair of different frequencies, with all clients'records stored in the Master. A ASK frame re-transmission principle and software watchdog timer (soft WDT) are proposed in order to guarantee steady data transmission in a wireless environment. Soft WDT also avoids the problem of dead-cyclic when we use wireless communicate. The system is finally successfully experimented. The accomplishment of steady data and voice transmission in this system not only proves that our solution conquers the demerits in wire communication, but also shows a direction for future aptitude door-guard system in residence cells.