Design of mobile phone anti-theft alarm system based on C8051F330

Introduction
With the rapid development of communication technology, there are more and more mobile phone users. According to statistics, there are about 300 million mobile phone users in China, with an average of one mobile phone for every four people. The number of users is still increasing rapidly, and the number of mobile phone loss incidents is increasing. Some are lost by users, but more are stolen. Therefore, it is particularly important to effectively prevent mobile phone theft or notify users in time when the mobile phone is stolen. In this regard, a mobile phone anti-theft alarm system is designed using the C8051F330 fully integrated mixed signal system-on-chip (MCU) and the wireless transceiver CC2500. The alarm system uses a radio frequency transceiver to achieve short-range information transmission.

2 System Design Scheme
The purpose of this system design is to send out an alarm message in time when the mobile phone is stolen to remind the user. Based on this, a mobile phone anti-theft transmitter and a mobile phone anti-theft transponder are designed here. The transmitter is placed on the mobile phone, and the transponder is designed as a keychain to be hung by the user. The two communicate in full-duplex mode, and the communication distance is adjusted through software and hardware design. The transmitter and the transponder have the same address and frequency. The transponder sends addressing information to the transmitter within the set time. If the transmitter receives the addressing signal and feeds back the response information within the set time, it means that the mobile phone is not likely to be stolen. On the contrary, if the mobile phone is stolen or far away from the safe distance, the transponder will send out an audible and visual alarm or a vibration alarm to remind the user. Figure 1 shows the system composition block diagram. Among them, C8051F330 is a mixed signal system on chip (MCU); CC2500 is used for radio frequency (RF) communication.

3 System Hardware Design
The hardware design of this system is mainly used to realize the RF communication between C8051F330 and CC2500. Since C805lF330 integrates a high-precision clock source, its internal 64 KB Flash is sufficient for the system. Therefore, when designing the oscillation circuit and storage circuit, there is no need to expand, only the power supply circuit, CC2500 communication circuit, and reset circuit need to be designed. This can make the system hardware design circuit structure simple, with high integration and good reliability. Figure 2 shows the schematic diagram of the system hardware design. In order to improve the communication speed and reliability of the system design, CC2500 can be used to enable the system to realize SPI communication with C8051F330 through the RF communication module VW2500. VW2500 and C805lF300 are powered separately through R3 to reduce the interference of RF signals to MCU and ensure reliable operation of the system.

4 System software design
The software design of this system is mainly used to realize the wireless communication between the transmitter and the transponder. According to the functions set by the user, the user is prompted in real time and the mobile phone's presence status and anti-theft information are issued. The software includes setting the address and communication frequency of the transmitter and transponder. Figure 3 shows the flow chart of the system software design.

5 Conclusion
The mobile phone anti-theft alarm system uses the highly integrated C8051F330 device and the RF communication device CC2500 to achieve real-time communication between the mobile phone and the user, effectively preventing the loss and theft of the mobile phone. Since the system uses C805lF330 and CC2500 as core components, it has a simple structure, stable performance, small size and low cost. It has been successfully used in mobile phone anti-theft alarms and has a very good effect.