Wireless Distributed Monitoring Terminal Used for On-Line Application

doi:10.4236/cn.2013.53B2099

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Communications and Network, 2013, 5, 549-553

http://dx.doi.org/10.4236/cn.2013.53B2099 Published Online September 2013 (http://www.scirp.org/journal/cn)

Wireless Distributed Monitoring Terminal Used for

On-Line Application

Fenggui Wang, Lin Zhang, Zhongmin Wang, Yanbo Zhang

Institute of Automation, Shandong Academy of Sciences, Jinan, China

Email: [email protected]

Received June 2013

ABSTRACT

A wireless distributed monitoring terminal was designed with embedded Linux used on the basis of ARM board, and an

application program was developed for data collection, processing and transmission. Data were collected from the sur-

rounding environment and transmitted to a server via WLAN in the form of Extensible Markup Language (XML)

stream, so the terminal had good flexibility to be compatible with different sensors, network devices and information

systems from multiple manufacturers.

Keywords: On-Line Monitoring; Distributed Monitoring; Extensible Markup Language (XML) Stream; Wireless

Terminal

1. Introduction

On-line applications are becoming more and more wide-

spread along with the popularity of the Internet of Things

in various fields [1], such as environmental monitoring,

public safety, telemedicine, etc [2,3]. In these applica-

tions, some terminals are necessary to execute data ac-

quisition, processing and transmission. There may be dif-

ferent sensors, network devices and information systems

from multiple manufacturers even if in one application,

so it is important that every terminal has good flexibility

to be compatible with them.

ARM platform has been very popular in the area of

mobile devices such as smart phones, personal players of

audio and video, GPS systems and so forth, and can also

compete with desktop computers based on i386 architec-

ture microprocessors in some case [4]. ARM microcon-

trollers are convenient and efficient for designing and

developing especially with embedded operating system

used, so more and more terminals begin to adopt designs

based on them nowadays.

This paper deals with design of a wireless distributed

monitoring terminal with embedded Linux used on the

basis of ARM board, and development of an application

program for data collection, processing and transmission.

It collects data from the surrounding environment via

RS485 or A/D convertor, carries out data analysis and

processing, and transmits them to a server via Wireless

Local Area Network (WLAN). The server stores these

data to an oracle database and presents them through web

pages. It is needed to be specially noted that these data

are encapsulated into Extensible Markup Language (XML)

stream by terminal before transmitting and then parsed to

obtain the semantics by server after receiving [5], so as to

enhance the flexibility of whole system.

2. Hardware Design

The hardware of the wireless distributed monitoring ter-

minal includes ARM9 board based on S3C2440A and

Wi-Fi module to send and receive data wirelessly be-

tween it and the server. Also, it connects temperature/

humidity sensor and illumination sensor as example for

monitoring changes of the surrounding environment. The

structure diagram of the terminal is shown in Figure 1.

2.1. ARM9 Board

The board is based on S3C2440A microcontroller with

512 MB RAM and 512 MB flash memory. SAMSUNG’s

S3C2440A is designed to provide hand-held devices and

general applications with low-power, and high-perfor-

mance microcontroller solution in small die size. To re-

duce total system cost, the S3C2440A includes the fol-

lowing components: separate 16 KB Instruction and 16

KB Data Cache, MMU to handle virtual memory man-

agement, LCD Controller (STN & TFT), NAND Flash

Boot Loader, System Manager (chip select logic and

SDRA M Con tro ll er), 3-ch UART, 4-ch DMA, 4-ch Timers

with PWM, I/O Ports, RTC, 8-ch 10-bit ADC and Touch

Screen Interface, Camera interface, IIC-BUS Interface,

F. G. WANG ET AL.

550

Figure 1. Structure diagram of wireless distributed monitoring terminal.

IIS-BUS Interface, USB Host, USB Device, SD Host &

Multi-Media Card Interface, 2-ch SPI and PLL for clock

generation [6]. The platform also offers a large number

interface to support peripheral equipments, including USB

host, USB device, LCD touch screen interface, RS232,

RS485, 4 - 20 mA/0 - 5 V convertor and so on.

2.2. Wi-Fi Module

The Wi-Fi module adopted based on VIA Networking

VT6656 is fully compliant with IEEE’s security and

802.11 g standards [7]. Enabling data rates between wire-

less devices of up to 54 Mbps, it can deliver the band-

width necessary for real-time streaming of high-defini-

tion digital multimedia content in home networks, and

provide high-speed email, web and LAN access to mul-

tiple mobile users in corporate environments or public

hotspots. Integrated WLAN into USB 2.0 with it, device

also makes it more convenient to get on the net anywhere

you are.

2.3. Sensors

The temperature/humidity sensor and illumination sensor

are used to collect data from the surrounding environ-

ment in our system.

1) Temperature/humidity sensor

This sensor adopts the most advanced digital sensor

technology, overcoming disadvantages of the traditional

analog temperature sensor, such as instability, much devi-

ation from accurate data, v ulnerability to interferen ce, and

requiring regular calibration. It processes the function of

collecting information of temperature and humidity, w ith

calculating data stably and accurately. Its operating vol-

tage can be as low as 12 V, accuracy of temperature

±0.7˚C, accuracy of humidity ±3% RH.

Connected to the monitoring terminal via RS485, an

industrial level communication network with long-dis-

tance transmission, high speed and high stability com-

pared with RS232, the sensor transmits acquired temper-

ature/humidity data using Modbus standard. It is an ap-

plication layer messaging protocol that is positioned at

level 7 of the OSI model and widely used in industrial

environment.

2) Illumination sensor

This sensor has a wide light measurement range of 0 ~

200,000 Lux, with high precision linear amplifier circuit

and high sensitive photographic detectors. Its accuracy is

less than ±7%, and operating voltage is 12 - 24 V.

After data acquisition, the sensor transmits 4 - 20 mA

current signal to the monitoring terminal, and then the 4 -

20 mA current signal is converted to 0 - 3.3 V voltage

signal. Through an analog-digital converter, digital data

are acquired and they can easily be processed and ana-

lyzed by S3C2440 to make them understood by human.

F. G. WANG ET AL.

551

3. Software Design

The linux-2.6.28 distribution compiled for ARM9 plat-

form is chosen as the operating system. The application

program residing on the ARM platform is written in C

language and compiled using the Linux GNU C compiler,

which can be downloaded from the network free of

charge.

3.1. Device Drivers

Device drivers take on a special role in Linux kernel.

They are distinct “black boxes” that make a particular

piece of hardware respond to a well -defined internal pro-

gramming interface, and the details of how the device

works are hidde n completely by them [8]. User activ ities

are performed by means of a set of standardized calls that

are independent of the specific driver, mapping those

calls to device-specific operations that act on real hard-

ware is then the role of the device driver. This program-

ming interface is such that drivers can be built separately

from the rest of the kernel and “plugged in” at runtime

when needed. This modularity makes Linux drivers easy

to write, to the point that there are now hundreds of them

available.

Linux device driver belongs to the kernel part, and

there are two ways of compiling and loading it into Li-

nux kernel. One way is to directly compile device driver

into the kernel, along with Linux starts when loading.

Another way is to compile device drivers as dynamic

loading and deleting modules, using the command of

“insmod” to load and “rmmod” to delete. This way con-

trols the size of the kernel, while the other way increases

redundancy of the kernel, so it is adopted to compile

USB wireless network card driver, exit key driver, A/D

driver, etc.

3.2. Work Flow

The monitoring terminal firstly initializes, including start-

ing Linux system, loading USB wireless network card

driver, exit key driver and A/D driver and setting serial

port, and sends archived data, which is stored in a local

file when the network is unconnected. Then real time

data is frequently acquired from sensors, analyzed by

classification, stored into local file, and sent in the form

of XML stream. When sent successfully, the data will be

deleted from the local file immediately. Due to being

stored into a local file first, data will not be lost even if

the terminal is powered down suddenly. Next, the ter-

minal will check whether the time point set beforehand

has arrived. If the time point is up, it will send archived

data stored in the local file, otherwise it still conducts as

before. Also, if the terminal detects the exit key has been

pressed, it will ex it normally including re leasing memory

closing devices, unloading drivers, etc. The work flow of

the terminal is shown in Figure 2.

4. Testing

There is a wireless distributed monitoring terminal tested

which collects data from the surrounding environment

and transmits them to a server via WLAN. These data are

stored to an oracle database and presented through web

pages, as shown in Figures 3 and 4.

5. Conclusion

In this paper, an embedded Linux operation system com-

bined with ARM9 platform is adopted to implement a

Figure 2. Flow chart of wireless distributed monitoring

terminal.

Power on &

Self-start

Load drivers

Analyze and store

the data

Receive successful reply?

Send the data

Delete the data

Time point has arrived?

Acquire real time

data

Three times？

Send archived data

Receive successful reply?

Delete historical

data

Send archived data

Receive successful reply?

Delete historical

data

Exit key pressed?

Exit

Start

F. G. WANG ET AL.

552

Figure 3. Data stored to oracle database.

Figure 4. Data presented through web pages.

F. G. WANG ET AL.

553

wireless distributed monitoring terminal, and an applica-

tion program is developed for data collection, processing

and transmission. Data are sent in the form of XML

stream, stored in oracle database and presented through

web pages, so it’s feasible to add any sensor to the ter-

minal. Future possible works based on this terminal are

adding more environment sensors and improving the

XML streami ng protocol .

6. Acknowledgements

The paper is supported by Youth Science and Technolo-

gy Star Program of Jinan City, China (Grant No. 20100105)

and Youth Science Funds of Shandong Academy of

Sciences, China (Grant No. 20100106). The authors would

like to thank all collaborators, especially who are in the

UWB & THz Innovation Team, Shandong Academy of

Sciences, China.

REFERENCES

[1] Wikipedia Foundation, “Internet of Things,” 2013.

http://en.wikipedia.org/wiki/Internet_of_Things

[2] T. Qiao and L. Song, “The Design of Multi-Parameter

Online Monitoring System of Water Quality Based on

GPRS,” IEEE 2010 International Conference on Multi-

media Technology (ICMT), 2010, pp. 1-3.

[3] W. Fu and X. Meng, “Remote Monitoring System Re-

search and Implementation Based on Wireless Commu-

nication,” 5th International Conference on Machine Vi-

sion (ICMV 12). International Society for Optics and Pho-

tonics, 2013.

[4] Wikipedia Foundation, “ARM architecture,” 2013.

http://en.wikipedia.org/wiki/ARM_architecture.

[5] F. Wang, H. Yang and D. Tian, “IM-based Communica-

tion Mechanism for an On-line Monitoring System,”

IEEE Proceedings of International Workshop on Intelli-

gent Systems and Applications, 23-24 May 2009, Wuhan,

2009, pp. 145-148.

[6] Samsung Electronics Co., Ltd., “S3C2440A 32-Bit RISC

Microprocessor User’s Manual (Revision 1.2),” 2004.

[7] VIA Technologies, Inc., “VIA Solomon VT6656-802.11a/b/g

Wireless LAN Controller with Integrated Baseband Pro-

cessor-USB 2.0 Bus Interface,” 2013.

http://www.via.com.tw/en/products/networking/wireless/

vt6656.

[8] J. Corbet, A. Rubini and G. Kroah-Hartman, “Linux De-

vice Drivers,” 3rd Edition, O’Reilly Media, 2007.