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Journal of Information, Control and Management Systems, Vol. 9, (2011), No. 2

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MODULAR APPROACH DURING ON-BOARD UNIT DEVELOPMENT Vojtech ŠIMÁK, Jozef HRBČEK, Juraj ŢDÁNSKY University of Ţilina, Faculty of Electrical engineering, Slovak Republic e-mail: [email protected], [email protected], [email protected] Abstract The aim of this paper is to give a description of a modular on-board unit. First chapter contains an idea of modularity. Following chapters are dedicated to created device. Keywords: on-board unit (OBU), microcontroller 1

INTRODUCTION The idea of the modular system was a result of an effort to create universal platform for the vehicle localization and monitoring. The platform contains several modules which can be activated or deactivated depending on purpose of use. For example this unit can be modified as a part of system for monitoring of transport of dangerous goods. For this purpose the SD card is unnecessary. In this configuration the unit is used as an online position monitoring OBU which is also able to log the data on SD card. This OBU was successfully tested in real traffic in Ţilina. The basic unit contains following modules (system’s structure is shown in the Fig. 1).

Figure 1 System structure

Modular Approach During On-Board Unit Development

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• • • • • • • • • •

Atmel MEGA 644 microcontroller with 64 kB flash, and 4 kB RAM LCD 128 x 64 graphic monochromatic display The GPS localization module interface (RS 232) GSM / GPRS module for communication between the on-board unit and monitoring center SD card slot for the data-logging USB interface (FTDI module) 3 programmable push-buttons and 4 DIP switches Buzzer for acoustic signalization Optionally the module for communication between the on-board unit and CAN-bus of vehicle can be attached Option for various analog and digital inputs / outputs

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HARDWARE MODULARITY The PCB design is created in the CADSoft – Eagle software. This board is a single layer (shown in Fig. 2). All modules are optional, for example, when there is no need to use the GPRS data transfer, the GSM/GPRS module and the LM317 voltage regulator are left out.

Figure 2 The component and wiring side of an on-board unit The core containing ATMEGA microcontroller, 7805 voltage regulator and serial port multiplexer are required for functionality. More information about the modular approach is described in [1] and [2]


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SOFTWARE MODULARITY The software for this on-board unit is created in the AVR Studio / WINAVR. The groups of commands are organized into the functions. For example the gsm_init() contains all compulsory commands for attaching to the GPRS service and for login to the server. All modules can be activated simply by using these functions. The program for the GPRS server and for the client was written in Visual studio. 4

GPS INTERFACE The position of the vehicle is obtained from the Navilock NL 403p module. This device is transmitting NMEA sentence through the RS232 interface (the MD6 connector) every second. 5

GSM / GPRS COMMUNICATION MODULE This module allows us to interchange information between the on-board unit and the surveillance server. At first it is necessary to establish the GPRS connection for this purpose. The security aspects of the data transfer are mentioned in [3]. The only problem during the GSM module testing was caused by a weak power supply. The GSM/GPRS module needs power supply with low internal resistance because the current can rise up to 2A impulses during the transmission. Further information about the AT commands can be found in [4]. The settings of GPRS parameters for Slovak GSM networks are described in [5]. 6

SD CARD Optional SD card can be used for data logging. The 2 GB card Sandisk was used in this test. The card is connected to the microcontroller via SPI interface. Because the microcontroller is operating at 5V level and the SD card is operating at 3,3V level, it is necessary to lower the voltage from the microcontroller by using a voltage divider. The SD card needs a voltage stabilizer to get enough current during its operation. Removing the SD card during programming has to be done because MOSI wire is not connected via voltage divider (because this is SD card output and microcontroller input) and 5V level can damage the SD card operating at 3,3V level. The first problem using the SD card was to find suitable library to access it. The site [6] where it is possible to download all suitable libraries was found after number of trials. This site contains also a discussion and the code samples. The second problem was to read the SD card using Windows operating system. The command for writing to file and FAT needs a specific format of file name and extension. Not respecting this file name and extension format causes compatibility problems with Windows operating system. Entering of an Incorrect file name leads to an incorrect file access in the Windows operating system. These files can be accessed

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by Ubuntu Linux operating system without any problems. More detailed information about data saving and communication is described in [7] and [8]. 7

USB / FTDI MODULE This module allows connection between computer with the USB interface and the on-board unit. Almost every modern computer has this interface, that is why the USB was chosen for the data transfer between computer and this unit. This module was tested only in the Windows / Hyperterminal software and it was used for debugging purpose for the GSM / GPRS module implementation. 8

CONCLUSION The device can receive GPRMC sentence from the Navilock NL403p module and send it to the server via GPRS. The next feature of this module is to write data to the SD card. During testing the on-board unit was placed in the vehicle (Kia Ceed 2009) and powered from 12V socket. The only problem that occurred was the shutdown during starting. The vehicle is switching off all appliances not needed for engine operation during starting. It results in the reset of all modules including the main microcontroller. Back-up battery attachment would be convenient for the future use. During test drive it was possible to follow the vehicle on the client interface. The onboard unit and the monitoring software are shown in Fig. 3. Further information about traffic monitoring is mentioned in [9]. The on-board unit development with similar purpose is described in [10] and [11].

Figure 3 The on-board unit during the test drive and software client for position monitoring 9

ACKNOWLEDGMENT This work has been supported by the project No. 26220120028; “Centre of excellence for systems and services of intelligent transport”


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REFERENCES [1] MACEK, P., MIČIETA, B. 2011. Intelligent modular system. In Automation and control in theory and praxis. Stará Lesná : Technical university in Košice, 2011 ISBN 978-80-553-0606-3, 2011, pp. 30-36. (in Slovak) [2] ROFÁR, J., STRÁPKOVÁ, J. 2011. MES Inplementation into intelligent production system. In Automation and control in theory and praxis. Stará Lesná : Technical university in Košice, 2011 ISBN 978-80-553-0606-3, 2011, pp. 44-50. (in Slovak) [3] HOLEČKO, P., KRBILOVÁ, I.: IT Security Aspects of Industrial Control Systems, Advances in Electrical and Electronic Engineering, No. 1-2 Vol. 5/2006, ISSN 1336-1376 pp. 136-139 [4] http://www.edaboard.com/thread152813.html [5] http://www.om7ajk.estranky.sk/clanky/nastavenia/nastavenie-internetu-a-wapupre-t-mobile_-orange-a-o2_ [6] http://www.mikrocontroller.net/topic/105869 [7] KUDLA, M., STRÉMY, M.: Alternative methods of semi structured data saving. In: Applied Natural Sciences 2007: International Conference on Applied Natural Sciences, Trnava, November 7-9, 2007. Book of abstracts. Trnava: University of SS. Cyril and Methodius Faculty of Natural Sciences, 2007, pp. 404-409, ISBN 978-80-89220-90-8. (In Slovak) [8] BÉLAI I., BALOGH I., DORNER J., DRAHOŠ P.: Industrial communication Vydavateľstvo STU, 2001. ISBN 80-227-1600-6. (In Slovak) [9] PIRNÍK, R., HALGAŠ, J., ČAPKA, M. 2011. Non-invasive monitoring of calm traffic. In Acta technica corviniensis – bulletin of engineering. Hunedoara Romania: University Politehnica Timisoara, 2011 ISSN: 2067-3809, 2011, pp. 111 - 115. [10] VACULÍK, M., FRANEKOVÁ, M., VESTENICKÝ, P., VESTENICKÝ, M.: On-Board Unit and its Possibilities of Communications on Safety and Security Principles. AEEE 7, 2008, No. 1-2, pages 235-238. ISSN 1336 – 1376 [11] VESTENICKÝ, P., VESTENICKÝ, M.: Simple On-board Unit for Active Support of Driver - Technical Solution. Transport and Logistic, 6th extraordinary number of journal, Košice, 2009, pages 457 - 460. ISSN 1451107X (in Slovak)

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