The Design of Wireless Data Collector based on WIA-PA Ligang Li 1,2,a, Zhongfeng Wang 1,2,b, Jianlong Huang 1,2,c

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1 Advanced Materials Research Online: ISSN: , Vols , pp doi:0.408/ 04 Trans Tech Publications, Switzerland The Design of Wireless Data Collector based on WIA-PA Ligang Li,,a, Zhongfeng Wang,,b, Jianlong Huang,,c Shenyang Institute of Automation, Chinese Academy of Sciences, Shenyang,china 006 Lab. of Networked Control Systems, Chinese Academy of Sciences, Shenyang,china 006 a lilg@sia.cn, b wzf@sia.cn, c huangjianlong@sia.cn Keywords: WIA, collector, transmitter, wireless communication. Abstract. This paper presents a design of wireless data collector based on WIA-PA. The wireless data collector collects analog signal of voltage or current, and transmits it to the host computer wirelessly. Through it, the traditional 4-0mA or 0-5V analog interfaced instrument can be easily accessed to the newly designed wireless data acquisition system, which saves wiring and maintenance costs. Introduction There are many measurement instrument in the industrial field, much of it is analog interfaced, they output 4~0mA or 0~5V signal. The instrument has advantages of simple structure and low cost, and specially 4~0mA output type has advantages of easy wiring. But the analog interfaced instrument need wiring installation to transmit signals. Wireless transmission can improve this problem. We can monitor instrument and sensor data in the distant place without complex wiring process, saving wiring and maintenance cost. This paper designs a new type of wireless data collector, which has the characteristics of high precision, low power consumption and real-time communication, by using the wireless module based on the WIA-PA technology. The traditional analog interfaced transmitter can be linked into the wireless measurement and control system by the data collector. In industrial measurement field, because of its advantages of low cost, low power consumption, easy installation and debugging, measuring instruments based on WSN(Wireless Sensor Network) are widely used. WIA-PA (Wireless Networks for Industrial Automation-Process Automation [] []) developed independently by China is a wireless network standard for industrial process automation. This technique is based on the IEEE standard, which provides an effective solution to realize remote data transmission of low energy wireless equipment. Platform Design As shown in Figure, the hardware of wireless data collector based on WIA consists of main control MCU, analog signal acquisition circuit, WIA wireless module, dial switches & buttons and LCD display module. This design chooses MSP40F47[] as the MCU. MSP40F47 is a microcontroller configuration with a 6-bit timer, a high performance 6-bit sigma-delta A/D converter(sd6_a), 4 I/O pins, and a liquid crystal display driver. The SD6_A module consists of one sigma-delta analog-to-digital converter with an internal voltage reference. It can easily collect the 4-0mA current signal or the 0-5V voltage signal. The liquid crystal display driver can support up to 8 segments. The serial port of the MCU is connected to the WIA wireless communication module. In addition, the MSP40F47 provides a power down detection, power supply monitoring function. All rights reserved. No part of contents of this paper may be reproduced or transmitted in any form or by any means without the written permission of Trans Tech Publications, (ID: , Pennsylvania State University, University Park, USA-09/05/6,07:54:6)

2 79 New Technologies for Engineering Research and Design in Industry Fig. System architecture Analog signal acquisition circuit. Analog signal acquisition circuit is shown in Figure. IO+, IO- are signal input terminal, R0 is the 4-0mA current sampling resistor, J0 is a switch, Rt0 and Rf0 set up a divider circuit, the divided voltage signal go through the PHOTOMOS relay AQW4. I0 is connected to the 6 bit A/D converter of MSP40F47. The AQW4 is controlled by MCU through the K0 pin. When J0 is closed, IO+, IO- can access current signal of 4 ~ 0mA; when J0 is off, the input would be 0 ~ 5V voltage signal. I0+ io io l- l- C0 04 I0- Rt0 J0 0k R0 50R C0 04 Rf0 0k RL0 V_ 7 5 U0 io io l+ l+ AQW4 8I0 6GND 4k0 Fig. Analog signal acquisition circuit LCD module. This design uses segment type LCD. The liquid crystal display driver of MSP40F47 can support up to 8 segments. This design uses a total of 6 segments, including four and a half numbers and special characters, they use three com terminals. Then connect the corresponding pin of the LCD module to the MCU, and place resistance between R0 ~ R pin of the MCU. The display effect is shown in Figure. Fig. LCD display Power supply circuit and wireless module interface. This design uses 0 ~ 0V DC power supply that is commonly used in the industrial field. In order to adapt to the wide voltage input range of 0 ~ 0V, the way of switching power supply with linear regulated is used to achieve DC/DC conversion. This paper chooses H406 as the switch power conversion chip, using BM7 as the.v regulator chip. The circuit is shown in Figure 4. Power supply of 0 ~ 0V DC is input to the module of switching power from the +Vs pin to obtain Vout5+. Then through the BM7 voltage regulator,.v power supply in VCC terminal is obtained. The diode N4007 is connected at the input of the power, preventing the power wrong polarity. A self recovery fuse is connected to ensure that the whole power supply system will not be affected when the system load anomaly becomes large. To improve the anti-jamming ability of power supply, a TVS tube P6KE47A is connected in parallel with the input, reduces the influence of the surge voltage.

3 Advanced Materials Research Vols D +Vs Dx R00 D TVS N4007 RSC C7 47U/50V R R0 0 U4 DRC IPK VCC FB SWC SWE TC GND H406A Vout5+ 4 +C5 470P L 00uH D +C u Vout5+ Z U7 BM7 IN C4 04 OUT GND VCC C9 06 Fig. 4 Power supply circuit WIAPA-M800 [4] which is fully compliant with WIA-PA specification is selected as the WIA wireless communication module. It is a highly reliable industrial wireless[5] product equipped with WIA-PA protocol stack, and can be regarded as a card with a serial port. The MCU can control it by the RXD and TXD pin. SOFTWARE DESIGN Software Process. The procedure of the system is shown in Figure 5. After initialization, the system firstly determines whether to enter the calibration mode by detecting the position of the buttons and dial switches. If entering the calibration mode, the calibration is done in accordance with the calibration process, and then waits for restart. If not entering the calibration mode, device ID and input signal type is set according to the dial switch state, and then low power mode is entered. It waits to be woken up and enters active mode by serial port interrupt, after completing the corresponding analog signal acquisition and communication task, it reenters the low power mode. Fig.5 Software flow chart Data acquisition subroutine. The on-chip 6 bit Σ- A/D converter is used in this design to convert analog signal. In order to get a stable and accurate measurement data, This design uses the

4 794 New Technologies for Engineering Research and Design in Industry median average filtering method, that is sampled once every 5ms, continuous acquisition of 0 times, taking the average of the middle 6 data as the final samples. Then the linear interpolation method is used by querying calibration table in the flash according to the current operating mode to calculate the input current signal or voltage signal values. Serial communication program. The communication between WIA module and the main control MCU is compliant with HART7.0 protocol, which is reflected in the two stages of setting up communication and real-time data transmission. Before joining the WIA-PA wireless network, WIAPA-M800 module needs to construct its own long address by reading the identification code of vendor ID, device type and device ID form the main control MCU. Vendor ID and device type is determined at the same time of manufacturing, and device ID is determined by the dial switch. After the wireless data collector joining WIA-PA network successfully, the PC can get measurements from multiple collectors. After identifying wireless collectors, the network manager periodically sends a command to read the data by the long address of the collector. Summary This paper presents a design of wireless data collector. This design has advantages of low-power consumtion, high-precision acquisition of 4-0mA or 0-5V analog signal. What s more, the traditional analog interfaced instrument can be easily accessed to the newly designed wireless monitoring system, which saves wiring and maintenance costs. Acknowledgement In this paper, the research was sponsored by the National High Technology Research and Development Program of China(86 Pro.)(Project No. 04AA0480). This work was supported by the Lab. of Networked Control Systems. References [] IEC660 Ed..0[S].WIA-PA communication network and communication profile, 009. [] Liang Wei, Zhang Xiaoling. WIA-PA: industrial wireless network for process automation system architecture and communication protocol of [J]. Instrument standardization and metrology, 009 ().0 6. [] Texas Instruments.MSP40X4XX Family User 's Guide[EB/OL] [4] Chinese Academy of Sciences, Shenyang Institute of automation,.wiapa-m800 technical manual [Z].00. [5] WANG Fuqiang, ZENG Peng, YU haibin. An Energy-Efficient Time Synchronization Algorithm for Wireless Sensor Networks[J]. Information and Control, 0,40(6).

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