With the rapid development of information technology, people are pursuing a comfortable living environment and have further requirements for the safety of their own homes. When the owner goes out, the monitoring system plays an increasingly important role as an important part of the security facilities. In the scheme introduced in this paper, based on the MTK platform with mature software system, the sensor and speaker are mounted on the GPIO port of the MTK chip, which is composed of a real-time, cost-effective, low power consumption and encounters. Anti-theft monitoring and alarm system with automatic alarm and other functions after abnormality. The system makes full use of the existing resources in the MTK system, and the development cycle is short. Under the condition that the user has higher and higher requirements on the real-time, price and self-defense of the monitoring system, the MTK, which is currently mainly used as a mobile phone development platform, will be used. The system was introduced to areas such as security.
1 MTK system introduction
1.1 MTK hardware platform
MTK is the abbreviation of MediaTek Co., Ltd., which is called MediaTek. MTK mobile phone system is the most complete mobile phone product solution used by domestic mobile phone designers and manufacturers. Its cost-effective and secondary development features are favored by mobile phone manufacturers. This solution selects MT6225 as the core chip, which integrates ARM7 core and DSP core. It can expand the external device through GPIO (General Purpose Input Output) of MT6225. With superior wireless communication characteristics and mature hardware and software systems, MTK6225 has become the most widely used, stable and mature mobile phone development platform.
1.2 MTK Software System
MTK provides a complete set of powerful, stable and reliable software platform. Familiar and skillful application of its software system written in C language, can use MTK software system for secondary development, and apply MTK platform in addition to mobile phone development. Outside the security, production and other fields.
1.2.1 MTK operating system
MTK uses the Nucleus real-time preemptive multitasking operating system, which has a KAL (Kernel Abstraction Layer) OS layer. It serves as the interface layer for MTK software and the Nucleus operating system, and provides various system services (such as timers, queues, memory management, and events) for tasks.
1.2.2 Basic software architecture
The top of the Nucleus operating system is the software architecture of the entire MTK system. It is mainly composed of RMI (Remote MMI), MMI (Man Machine Interface), L4 (Layer 4), Drivers and PS/L1 (Protocol Stack/Layer 1). . The MTK software architecture uses the concept of a layer, which divides each functional module into different layers, each with its own functional characteristics. MMI is the core part of the secondary development of MTK system. The four main parts of FrameWork (framework layer), MMI and L4 layer communication, Application (application layer) and UI Layer (UI layer) constitute the overall architecture of MMI.
2 Functional description and overall framework of the system plan
The sensor is mounted on the GPIO port of the core chip MT6225 of the MTK system, and the output signal of the sensor is detected by periodically polling the state of the GPIO port. Once the MTK system detects the sensor output signal, the MTK platform starts the recording program to record the video, and drives the speaker to make a harsh sound. When the thief is expelled and the alarm is issued, the signal is sent to the owner by means of automatic short message. The video captured on the MTK platform and stored in the memory card of the MTK system makes it easy to find strong evidence. The overall framework of the anti-theft monitoring system based on the MTK platform is shown in Figure 1.
Figure 1 The overall framework of the anti-theft monitoring system based on the MTK platform
3 sensors and speakers
3.1 Sensor
A sensor is a power output device or device that converts a non-electricity into a deterministic relationship with it, and is essentially an interface between a non-electrical system and an electrical system. As a sensor that provides information for the anti-theft device, a piezoelectric sensor with a piezoelectric effect in the physical sensor should be selected and installed in the door, window, etc. of the home. When a thief enters, the sensor will be subjected to pressure, mechanical shock and vibration. The physical signal is converted into an electrical signal.
3.2 Speaker
A speaker, also known as a speaker, is a conversion device that converts electrical energy into sound. When different electronic energy is transmitted to the coil, the coil generates an energy that interacts with the magnetic field of the magnet, and this interaction causes the paper tray to vibrate. Because the electron energy changes at any time, the coil of the horn will move forward or backward, so the horn's paper tray will follow the movement, which changes the density of the air to produce sound.
As a power device, only the two connectors that are led out behind the speaker are connected to the positive and negative poles correspondingly, and as long as the voltage reaches a certain magnitude, a high-decibel harsh sound can be emitted. This program selects the horn as a device for expelling thieves and alarms. Connect the positive pole of the horn to the power supply, and the negative pole to the corresponding GPIO port of the MTK platform. When the MTK platform receives the signal generated by the sensor, the MTK platform pulls the GPIO port low, and the horn can work normally.
4 MTK timer, video and SMS function
4.1 MTK timer
A timer event is the repeated triggering of a specified event at a specified time or interval. This specified event is implemented by a registered function. In the MTK platform, the specific process of operating the timer is as follows:
1 Define your own TimerID in the MMI_TIMER_IDS enumeration type in the header file TimerEvents.h that defines the timer ID. The ID defined in the experiment is MY_TIMER_ID.
2 Start a timer using the function StartTimer (U16 TimerID, U16 delay, FuncPtr funcPtr), where TimerID is the clock ID, delay is the time interval, and funcPtr is the callback function of the timer event. Once the StartTimer is executed, the system will notify the execution of funcPtr when the time interval delay is reached. The start timer in the test is as follows:
StartTimer (MY_TIMER_ID, 1000, capture_and_send_message)
1000 is the time for scanning the GPIO port according to the timing set by the operating frequency of the MT6225 chip, and 1000 is 1 s in the MT6225. The function capture_and_send_message is a function written by the author and sent to the owner.
3 Whenever the program is exited, the timer event corresponding to the TimerID is stopped by calling StopTimer (U16 TimerID). The call situation in the experiment is StopTimer (MY_TIMER_ID).
4.2 MTK recording function
As a mobile phone development platform, the MTK system has the same functions as an ordinary mobile phone. Video is an important part of the current multimedia function of mobile phones, and this function can be used to collect important evidence. After receiving the signal generated by the sensor, the MTK platform starts the timer, and only needs to call the initialized initialization function and the function of recording, and then starts the recording function.
4.3 MTK SMS function
The SMS function is also an important part of the MTK software system. When the monitoring system alarms, the owner is notified by SMS, which not only prevents the further development of the unfavorable situation, but also submits the evidence immediately. The MTK itself has a short message communication function module, and the software system is modified. By setting a fixed number, the MTK system will automatically send a message to the number when an abnormal situation occurs.
5 Test process and results
By the signal generated by the GPIO0 high level analog sensor of the MTK chip, the positive pole of the buzzer is connected to the power of the MTK chip, and the negative pole is connected to the GPIO43. The MTK system checks the status of GPIO0 every 1 s by means of a timed inquiry. When the MTK system checks that the status of the GPIO0 port is high, the MTK system stops querying the GPIO port and starts the recording program. After the program is set to record for a certain period of time, the recording is stopped and the captured video file is saved to the local memory card of the MTK system. While sending GPIO43 low to drive the buzzer to sound, send a message to inform the owner. The experimental results show that the scheme is feasible and has good development prospects.
Conclusion
The MTK system provides a ready-made software and hardware platform, and introduces the MTK system belonging to the mobile phone development field into the fields of security and production as the control core, which not only reduces the development difficulty, but also avoids the main control unit commonly used in the monitoring system (such as ARM, FPGA, etc.) high price. More functional development of MTK has yet to be applied by MTK engineers in other areas besides mobile phones.
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