Research on Smart Home System Based on PXA270-Linux
Smart Home is a comprehensive integrated home service and management system consisting of a home security system, a network service system and a home automation system through the integrated use of advanced computer, communication and control technology (3C) to achieve comprehensive security protection. Convenient communication network and family home in a comfortable living environment. Smart Home is a versatile technical system that includes video intercom, home security, home wiring system, lighting control, home appliance control, remote video surveillance, sound monitoring, and home audio and video systems. With the development of technology and the growth of people's needs, home intelligence will contain more content.
1 Smart home system structure The current complete smart home system mainly consists of five parts: main control module, electrical control subsystem, lighting control subsystem, safety control subsystem and network control subsystem. Each of the five functions functions in a logical manner and constitutes a complete control entity. The entire system provides people with a smart, comfortable and secure home environment while providing remote information monitoring capabilities. The composition of the smart home system is shown in Figure 1. The main control module is responsible for the information concentration, storage, analysis and decision making of the subsystem. The development of embedded chips has made the main control modules more and more sophisticated and increasingly functional.
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Smart home is a huge system, the main control system is the control center of the system, the home network is the nervous system of the system, and the information flow and control flow of the transmission system. There are many devices in the home, and the interfaces of the devices are different. It is a huge challenge to realize the intelligent control of various devices. The design uses a distributed technology, bus technology and embedded technology to construct a smart home system with multi-functional and communication capabilities.
2 Development platform selection and construction
2.1 Intelligent home system hardware constitutes the main control platform: UP-SmarHome intelligent home teaching experiment system belongs to a comprehensive teaching experiment system. The main processor selects the PXA270 processor based on ARM core Intel XScale architecture, which integrates the storage unit. Peripheral controllers such as controllers, clock and power controllers, LCD controllers, and AC97 controllers can implement rich peripheral interface functions. Its low power operation mode and dynamic power management technology can effectively reduce the power consumption of the power supply. The built-in LCD controller and touch screen controller simplify the circuit design of the LCD display. The system uses a 16 b 8 inch 640 x 480 true color LCD display and touch screen. The PXA270 processor has a clock speed of up to 624 MHz, high computing power and low power consumption. It can meet the computing requirements of the main control module. It has rich peripheral interfaces and provides good support for the expansion of the main control module. Users can design their own interfaces for other modules. Function implementation.
2.2 Embedded Development Software Platform Embedded hardware resources are increasingly rich, and the cost is also low. The enhancement of resources enables software to have more resources available. In this design, the hardware resources of the main control module are very rich, and the software system is also very large. The software system cannot avoid the problems of conflict, data synchronization and data exchange when accessing resources, so an embedded operating system is needed to uniformly manage hardware resources. It provides a good foundation for software development. This system is developed on a Linux operating system with open source and portability.
2.2.1 Bootloader Bootloader Bootloader is the first link of embedded system software development. It is the first piece of code that runs after the target board system is powered on. By initializing the hardware device, the mapping table of memory space is established. Finally, the operating system kernel is loaded to establish an appropriate system hardware and software environment. The bootloader is strictly dependent on the hardware, and the universal bootloader is almost impossible. Here, U-boot is an open source project that complies with GPL terms and can support as many embedded processors and embedded operating systems as possible. This system successfully ported U-boot on the PXA270 development board.
2.2.2 Linux Kernel Porting and Compiling The so-called Linux porting is to make the Linux operating system necessary to rewrite the specific target platform, and then install it to the target platform to make it run correctly. This concept is currently being talked about in the field of embedded development. The basic content is: obtain a certain version of the Linux kernel source code, make necessary rewrites of the source code according to the specific target platform, and then add some peripheral drivers to create a new operating system suitable for the target platform, and target the system. Cross-compilation of the target platform, generating a kernel image file, and finally programming (installing) the image file into the target platform. Usually, it is difficult to rewrite the Linux source code. The file given by the target platform provider is used here. If some hardware in the system is not driven, you need to develop the driver yourself.
3 software design
3.1 Main control module software design The smart home main control module has rich hardware resources, and the software has the support of Linux operating system. Each sub-module works together under the control of the main control module. The main control module and the submodule mainly transmit information flow and control flow. The main control module to sub-module transmission is mainly the control flow, which completes the configuration of the sub-module or commands the sub-module system to complete a specific task. The sub-module to the host transmits mainly the data stream, and the data stream mainly includes the running status or sensor data of each device in the sub-module system.
The main function of the main control platform software is system initialization, establishing a human-computer interaction interface, realizing communication with GSM, and communicating with various monitoring and control modules.
In the initial use, the user sets the mobile phone number, the number will be saved in the FLASH configured on the main control platform, and the main control platform waits for the user command. This command may come from the GSM module or the current main control human-machine interface, when the user sends a short message to When the system sends a control message, the GSM module sends the received short message to the main control platform through the serial port, and the main control platform parses the short message, and assembles the message into a command frame, and sends the message to the controlled module through the RS 485 bus; From the current main control platform, the main control platform directly parses the command, and the assembly command frame is sent to the corresponding control module.
3.2 After sub-module software design sub-module initialization, periodically query the RS 485 bus interface to detect whether there is a command frame. If there is a received frame, the machine number in the frame is compared with the machine number of this module. If they are the same, Parse this frame and execute the corresponding command, otherwise continue to detect the bus interface.
4 Conclusion The structure of the home control network is analyzed. A smart home control system based on PXA270 processor and Linux operating system is proposed. The system software and hardware platform design is analyzed. Finally, the software design of the main control module and sub-module system and the RS 485 bus communication protocol between the main control module and other functional subsystems are introduced. The scheme has the advantages of flexible design, strong cutting ability, high integration and easy upgrade. The follow-up work should be further improved and improved on the basis of this to improve efficiency and practicability.
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