Application of ARM and Linux embedded systems in underground coal mines

1 System hardware structure design

(1) System structure

The system consists of an embedded controller, a remote monitoring station, a front-end data collector and corresponding splitters. The front-end sensors include temperature, pressure and gas concentration collectors. The system structure is shown in Figure 1.

(2) System hardware design

The core of the system hardware design is the embedded controller, and its hardware structure is shown in Figure 2.

1) ARM-S3C2410 chip. ARM processor is a 10-bit processor chip based on ARM core produced by different chip manufacturers through authorization by ARM (Advanced RISC Machines). S3C2440 is a powerful and low-power ARM9 embedded CPU launched by Samsung. Its main features are:

a. 200 MHz ARM920T core, supporting JTAG emulation debugging.

b. External memory control (SDRAM control and chip select logic), divided into 8 banks, each bank can access 128M space.

C. On-chip 4 KB SRAM can be used as NAND Flash system boot.

d. LCD controller (supports up to 4K color STN and 256K color T), 1-channel LCD dedicated DMA, etc. This high degree of integration not only facilitates the hardware design of the system, but also improves the stability and reliability of the system?[page]

2) Main features of system environment Linux

a. It adopts modular design and the source code is completely open. Anyone can modify it as needed and release it under the GUN protocol.

b. It has powerful network functions and can provide various network services.

c. It has rich software resources. Almost all Unix application software can be ported to the Linux platform.

d. Support multiple architectures, such as ARM, SPARC, X86, etc.

(3) System working principle

The main part of the temperature collector is the temperature sensor PH100TMPA, which has precise resolution and high accuracy; the pressure collector uses the GD-307 of Shaanxi Hongxiang Technology Development Co., Ltd., which can automatically convert the top plate pressure of the working face into a standard electrical signal and transmit it to related equipment; the gas concentration collector uses the Italian OGGI explosion-proof gas sensor, which has high sensitivity and can measure various gases such as O/NH,/CO/H:S. The hardware part of the splitter is the single-chip microcomputer AT89S52 and the serial level interface chip MAX483, which are mainly used for data transmission and control signal addressing. The remote control station is a PC and its required supporting devices.

The embedded controller is connected to the remote control station through Ethernet based on TCP/IP protocol, and connected to the splitter using RS485 fieldbus. The front-end collectors are distributed at various monitoring points in the mine, responsible for collecting pressure, temperature and underground gas concentration data in real time, and then transmitting the collected data to the embedded controller through the RS485 fieldbus via the splitter. The disperser receives the control signal of the embedded controller, switches the corresponding detection point, and uploads the data collected by the front-end sensor to the embedded controller. The embedded controller is responsible for receiving the data uploaded by each front-end sensor, processing the data in real time, and then sending the processed results to the remote monitoring station via Ethernet for further analysis by technicians.

2 Software Design

(1) System operating environment

The system operating environment mainly consists of the embedded controller motherboard startup program BootLoader, Linux kernel, root file system cramfs, initialization process, device driver, etc. It provides low-level services for applications. The device driver enables the embedded operating system to access and control peripheral devices so that these devices can work under the system. The device drivers in this system include CS8900A network card driver and other communication interface drivers, which are responsible for completing the low-level work of system communication.

(2) Application Design

The application mainly runs on the embedded controller, responsible for sending, receiving and processing data, and controlling the corresponding peripherals. Its flow chart is shown in Figure 3.

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The embedded control application uses a watchdog process and an instruction execution process. The watchdog process is responsible for monitoring the RS485 bus port, network port and data transmission. After the embedded controller application is initialized, the watchdog process runs. On the one hand, it monitors the service request of the remote monitoring station. When the service request command arrives, it first parses the command, determines the execution object of the command, and then hands it over to the execution process for execution. On the other hand, it receives the data sent by the splitter, reads the received data for standardized processing, and determines whether the conditions of the mine are within the normal range. If so, the processed results are sent to the remote monitoring station for further processing. Otherwise, an emergency interrupt signal is sent to trigger the alarm to take corresponding measures.

Linux serial port application development, UART is serial communication, operations include data sending, data receiving, interrupt, baud rate, modes include loopback, infrared, automatic flow control. Arm and serial port communication configuration: ① Save the original serial port configuration; ② Activate local connection and receive enable; ③ Set input and output baud rate; ④ Use mask to set data bit; ⑤ Set parity bit; ⑥ Set stop bit; ⑦ Set minimum character and waiting time.

3 Conclusion

This system uses embedded Internet technology to achieve online real-time detection of temperature, humidity and gas concentration in the mine, and can detect the conditions in the mine at any time, which is very helpful in preventing accidents in the mine. The system has stable operation, high reliability and strong anti-interference ability, and has achieved the expected design purpose.