Design and implementation of real-name management system based on PXA270 platform

1 Introduction
China has rich coal resources. The comprehensive development of resources has brought about a series of problems in the comprehensive management and safety monitoring of mining areas. Here, a design scheme of a real-name management system based on the PXA270 platform is proposed. It can complete the comprehensive management of miners' information and the real-time monitoring of mining area safety, and realize the integration of information management and real-time safety monitoring.

2 Introduction to the YL_PXA270P Development Experimental Platform
The YL_PXA270P development experimental platform uses Intel's new generation XScale processor PXA270IlI. This device introduces the multimedia expansion function of the X86 architecture Pentium 4 series, and adds Intel Speed ​​Step dynamic power management technology, which greatly reduces the power consumption of mobile devices while ensuring CPU performance. YL-PxA270 provides complete underlying operating system support and rich application interfaces. It is suitable for embedded industrial control, digital media playback, interactive set-top boxes, car GPS and other applications. At the same time, YL_PXA270P includes: 2 9-line full-duplex asynchronous serial ports with a baud rate of up to 921 600 b/s; 1 5-line hardware flow control asynchronous serial port with a baud rate of up to 115 200 b/s; 1 10M standard Ethernet interface with connection and transmission indicators: 1 10M, 100M standard Ethernet interface with connection and transmission indicators. The experimental platform is equipped with a 256K color 640×480/6.4-inch TFT LCD screen with a touch screen, and the screen resolution can reach 800×600 pixels; a 50-pin LCD interface leads out all signals of the LCD controller and touch screen.

3 System design composition
The whole system design consists of three parts: comprehensive information management, regional information management and monitoring terminal. Figure 1 is a block diagram of the system design composition. Among them, the comprehensive information management is used as a remote server to realize database operations, Socket communication and real-time log recording. The partition information management is implemented on the PXA270 platform, and the two are connected through the RJ45 interface. The partition information management is used as a client to exchange data with the comprehensive information management (server) through the TCP/IP protocol. At the same time, it is connected to the monitoring terminal through the RS422 interface. The monitoring terminal realizes card information reading and sensor signal processing.

4 Comprehensive Information Management
Comprehensive information management consists of database, Socket communication and regional information display, and is developed using VC++6.0. The database uses Access database, and the underlying access is completed through 0DBC driver. The user identity is verified in the login module. Ordinary users can only perform query operations; administrator users can add, delete and modify database records. At the same time, the system regularly backs up the database to prevent data loss and damage. When the monitoring terminal detects an abnormality, it reports to the partition management system. The partition information management logs and uploads the recorded data to the server. Each item of the tree control corresponds to each partition, and displays the current connection status of each partition, partition employee information browsing, partition monitoring status and information. In the database, each partition system corresponds to a data table (Recordset), and the table item content and structure are shown in Figure 2.

5 Partition Information Management
Partition information management is based on the YL_PXA270P experimental development platform, which is used to realize network communication, serial communication, Nand-Flash file system, LCD/touch screen driver, keyboard control and other functions. The function menu options are realized by GUI, and the corresponding function selection is realized by touch screen and a 3×4 matrix keyboard. Figure 3 is a block diagram of partition information management. [page]

5.1 Implementation of the file system
The PXA270 platform uses K9F1208 Nand Flash with a capacity of 512M bytes, a total of 4 096 blocks, each block is 16 K bytes, contains 32 pages, and each page is 528 (512+16) bytes. Erasing is done in blocks, and reading and writing is done in pages. For the traditional FAT file system, since file operations require repeated operations on the file allocation table area, and the number of erase and write times of Flash is limited, the FAT file system needs to be improved. In addition, since the format of the partition information management data file is relatively fixed. That is, the employee information record file (each employee information record is a fixed number of bytes), the log file, and the command word file. For the employee information record file, the operation is not frequent, while the log and command word files are frequently operated. Therefore, when designing the file system, the first block of Flash (16 K+512) is used as the system record area of ​​the file system, and a blank area is established to record the starting address of the FAT table in the Flash. The FRT table is after the FAT. The write operation is in pages, so 8K space can record 16 addresses, which can avoid repeatedly erasing the FAT table in the same block, which shortens the memory life. Set an erasure threshold f (such as 50,000 times). When it exceeds, the FAT table is moved to a new block, and the pointer changes, adding new address records. Figure 4 shows the block diagram of the file system operation principle.

5.2 Touch screen control
The PXA270 development platform has a 4-wire resistive touch screen. The controller uses UCB1400BE. The resistive touch screen has two resistive layers, one for horizontal drive and the other for vertical drive. UCB1400 applies voltage in a certain direction. When a pen touches the touch screen, the contact is connected, and the voltage in the other direction changes. Through A/D conversion, the controller can calculate the coordinate value of the contact. When contact is made, UCB1400 issues an interrupt request. PXA270 responds to the interrupt, starts communication, reads the conversion result of UCB1400, and thus obtains the coordinates of the contact.

6 Monitoring terminal
The monitoring terminal uses the STC89C52 single-chip microcomputer as the control core, and integrates voice recording and playback control, infrared pyrolysis instrument, gas sensor, serial communication module, keyboard and LED indicator module. Its composition block diagram is shown in Figure 5.

The voice recording and playback part uses ISD2560. This voice device uses the unique direct analog storage technology DAST (Direct Analog Store Technology) of the American ISDN company. This technology allows audio information to be accessed without traditional A/D conversion and D/A conversion, and has higher integration and sound quality than the same digital access. At the same time, the device also has a power-off resistance function, supports multiple recording and playback operations, and can be used as a single chip or cascaded. Its on-chip E2PROM capacity is 480 K, with 10 address input terminals, addressing capacity of 1 024 bits, and can be divided into up to 600 segments. ISD2560 working principle: When recording. The microphone collects a small signal from the MIC, which is output from the ANA OUT (analog output) after preamplification, and is sent to the ANAIN (analog input) after passing through the DC isolation capacitor. The signal entering ANA IN passes through the amplifier, automatic gain control (AGC) and low-pass filter, and is finally written into the E2PROM through the analog transceiver. In the playback mode, the recorded analog voltage is under the control of the sampling clock. It is read out sequentially from the analog storage array and then sent to the power amplifier, output from the SP+ and SP- terminals, and directly drives the speaker. There are 10 address lines, of which A0~A7 are connected to the MCU PO port, and A8~A9 are connected to P2.0~P2.1. And EOM, PD.CE.P/R are connected to the P1 port. SP+ and SP- directly drive the speaker, but the volume is small; the audio amplifier LM386 is used in the actual design, and the volume is adjusted by adjusting the potentiometer R30. The circuit is shown in Figure 6.

[page]

The gas detection of the sensor circuit adopts the KGS-20 combustible gas sensor, which is a semiconductor gas sensor with tin dioxide as the basic sensitive material. It is specially used for the detection of the concentration of combustible gas. It has extremely high sensitivity, extremely fast response speed and low power consumption. The infrared sensor adopts LHl958 and uses the BISS0001 infrared sensor signal processor. The signal processor has an independent high input impedance operational amplifier, which can match a variety of sensors; it has a bidirectional amplitude detector, which can effectively suppress interference; it has a built-in delay timer and a latch time timer. When in use, the operational amplifier OP1 amplifies the output signal of the pyroelectric infrared sensor in the first stage, and then couples it to the operational amplifier OP2 for the second stage amplification by C30. It is then processed by the bidirectional amplitude detector composed of voltage comparators COPl and COP2. Detect the effective trigger signal Vs to start the delay timer, and the output signal Vo is amplified by the transistor VT1 to drive the relay to connect the load. The monitoring part of the circuit is shown in Figure 7. Figure 8 is the main program flow chart of the monitoring terminal.

7 Conclusion
The system takes the YL-PXA270P experimental development platform as the core. Through the interconnection and information interaction of the three subsystem modules of comprehensive information management, partition information management, and terminal monitoring, the real-name management is realized, and the functions of centralized information management, safety monitoring, and real-time recording are completed. In practical applications. As a remote server, the comprehensive information management provides operations such as browsing, adding, modifying, and deleting employee information, and exchanges information with the partition information management system through the network, relying on the Internet to achieve remote connection. The partition system records the employee information and safety monitoring logs in this partition, and sends the update logs to the server in real time. The monitoring terminal is placed in the mine, records and reads the radio frequency card information, identifies and records the attendance of employees, and uses sensors to monitor the environment in real time. After testing, the system runs stably and reliably, and has good practicality.