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1、Research and Development of the Remote I/O Data Acquisition System Based on Embedded ARM PlatformINTRODUCTION With the wide use of the networked, intelligent and digital distributed control system, the data acquisition system based on the single-chip is not only limited in processing capacity, but a
2、lso the problem of poor real-time and reliability. In recent years, with the rapid development of the field of industrial process control and the fast popularization of embedded ARM processor, it has been a trend that ARM processor can substitute the single-chip to realize data acquisition and contr
3、ol. Embedded ARM system can adapt to the strict requirements of the data acquisition system, such as the function, reliability, cost, size, power consumption, and so on. In this paper, a new kind of remote I/O data acquisition system based on ARM embedded platform has been researched and developed,
4、which can measure all kinds of electrical and thermal parameters such as voltage, current, thermocouple, RTD, and so on. The measured data can be displayed on LCD of the system, and at the same time can be transmitted through RS485 or Ethernet network to remote DAS or DCS monitoring system by using
5、Modbus/RTU or Modbus/TCP protocol. The system has the dual redundant network and long-distance communication function, which can ensure the disturb rejection capability and reliability of the communication network. The new generation remote data acquisition and moni- toring system based on the high-
6、performance embedded ARM microprocessor has important application significance. STRUCTRUE DESIGN OF THE WHOLE SYSTEM The whole structure chart of the remote data acquisition and monitoring system based on embedded ARM platform is shown in Figure 1. In the scheme of the system, the remote I/O data ac
7、quisition modules are developed by embedded ARM processor, which can be widely used to diversified industries such as electric power, petroleum, chemical, metallurgy, steel, transportation and so on. This system is mainly used for the concentrative acquisition and digital conversion of a variety of
8、electrical and thermal signals such as voltage, current, thermal resistance, thermo- couple in the production process. Then the converted data can be displayed on the LCD directly, and also can be sent to the embedded controller through RS485 or Ethernet network communication interface by using Modb
9、us/RTU or Modbus/TCP protocol. The data in the embedded controller platform is transmitted to the work- stations of remote monitoring center by Ethernet after further analyzed and pro- cessed. At the same time, these data can be stored in the real time database of the database server in remote monit
10、oring center. The system has the dual redun- dant network and long-distance communication function, which can ensure the disturb rejection capability and reliability of the communication network. The hardware platform of the Remote I/O data acquisition system based on emb- edded ARM uses 32-bit ARM
11、embedded microprocessor, and the software plat- form uses the real-time multi-task operating system uC/OS-II, which is open- source and can be grafted, cut out and solidified. The real time operating system (RTOS makes the design and expansion of the application becomes very easy, and without more c
12、hanges when add new functions. Through the division of the appli- cation into several independent tasks, RTOS makes the design process of the application greatly simple.Figure 1 Structure of the whole systemTHE HARDWARE DESIGN OF THE SYSTEM The remote I/O data acquisition system based on embedded AR
13、M platform has high universality, each acquisition device equipped with 24-way acquisition I/O channels and isolated from each other. Each I/O channel can select a variety of voltage and current signals, as well as temperature signals such as thermal resis- tance, thermocouple and so on. The voltage
14、 signals in the range of 0-75 mV ,1- 5V ,0-5V, and so on, the current signals in the range of 0-10mA and 4-20 mA, the thermal resistance measurement components including Cu50, Cu100, Pt50, Pt100, and the thermocouple measurement components including K, E, S, T, and so on.Figure2. Structure of the re
15、mote I/O data acquisition system based on ARM processorThe structural design of the embedded remote I/O data acquisition system is shown in Figure 2. The system equipped with some peripherals such as power, keyboard, reset, LCD display, ADC, RS485, Ethernet, JTAG, I2C, E2PROM, and so on. The A/D int
16、erface circuit is independent with the embedded system, which is independent with the embedded system, which is system has setting buttons and 128*64 LCD, which makes the debugging and modification of the parameters easy. The collected data can be sent to the remote embedded controller or DAS, DCS system by using Modbus/RTU or Modbus/TCP protocol through RS485 or Eth- ernet communication interface also, and then be used for monitoring and control after farther disposal.
