Design and Development of a Tablet Based Real Time Wireless Data Logger

Transcription

1 Design and Development of a Tablet Based Real Time Wireless Data Logger Zhan Wei Siew, Chen How Wong, Shee Eng Tan, Hou Pin Yoong, Kenneth Tze Kin Teo Modelling, Simulation & Computing Laboratory, Material & Mineral Research Unit School of Engineering and Information Technology Universiti Malaysia Sabah Kota Kinabalu, Malaysia msclab@ums.edu.my, ktkteo@ieee.org Abstract To date, data loggers are getting more implementation in business and home applications compare with several years ago. Data loggers can be customized according to the application requirement based on the available resources in the market. Thus, this creates a cost effective solution for the end user. In this paper, a wireless data logger with remote control capability via PC and tablet is introduced. The proposed wireless data logger is developed using microcontroller with analog-to-digital converter (ADC). The design of the portable wireless data logger is compact and light to increase the mobility and usability. Sampled data with time stamp from real time clock (RTC) module will be stored into SD memory card which is attached to controller board. Wireless data logger can directly transmit the data to end user if the device is in the communication coverage or stored the data into memory card if it is out of range. Graphic user interface (GUI) developed using Visual Basic and Android application. These applications can communicate with wireless data logger through wireless XBee module and Bluetooth module. End user can change the data logger settings such as, data sampling frequency, date and time remotely. Keywords wireless communication; data logger; microcontroller; Android I. INTRODUCTION Electronic devices that have the capability to record data from sensors in specific location over time are referred as data loggers. Typically, data logger is equipped with microprocessor, memory, and sensor for data collection. Mobility is one of the advantages of data logger since the size of the microprocessor, memory, and sensor is small. The design of the data logger can be made based on the needs of specific environment or application type. Many of the general purpose data loggers are machines with fixed parameters. However, there are some with re-programmable capability. One of the most important advantages of using data logger is the capability to collect data automatically over a long period. Measurement results can be collected without human supervision just by deployment and activating the data logger on the intended location. This does not only reduce the human resources in data recording, but also provide an accurate picture of the environmental conditions during the monitoring period. For most of the scientific research works, monitoring and collecting data of the phenomenon for a given period is very important to draw conclusion from analyzing the data. For the case that requires monitoring done in a large space environment such as in agriculture, [1]-[3] and weather station [4], [5], multiple of wireless data loggers are required to cover all the area. It forms a wireless sensor network problem. Many researches such as in [6]-[8] focus on prolonging the network life time since it is battery powered. To extend the operation times, technology such as mechanical generators, thermoelectric generators, and solar cells are use to harvest energy from the surrounding. Continuous development of the emerging technology on data logger has brought the creation of new innovation and applications. By using the available resource in the market such as personal computer and tablet [9], it is possible to customize data logger according to their application requirements. The content of this paper is organized as follows. In the next Section, the design of the wireless data logger is explained. The hardware development of data logger and mobile portable data logger is described in Section III. After the development of the hardware, software development will be carried out in Section IV. The software development includes the development of the source code for data logger and monitoring software. Section V presents the future work and the conclusion of this paper. II. THE DESIGN Wireless data logger provides decision making, real time data logging, data storage and wireless data transmission capability. In this Section, two data logging methods will be demonstrated. The first method is PC based data logging as shows in Fig. 1. The developed data logger has an ability to directly transmit the sensed data to PC-end use for real time monitoring. This method is very suitable for data logging in experimental and plant monitoring. The PC is always located at a place with electric supply, shelter and internet access. The data logging method can be enhanced by adding internet access to the PC and short message service (SMS) via Global System for Mobile (GSM) modem. Fig. 2 shows the alternative way of data logging in this paper. Sometimes, the data logger may be located at the place where it is far away from PC. Therefore, to retrieve the /12/$ IEEE 111

2 information, the user has to physically retrieve from the data logger. Introduction of a mobile portable data logger provides an alternative way to collect the data from data logger. Portable data logger can download data from data logger when the device is in the data logger communication coverage. In addition, the use of Tablet with the mobile portable data logger provides data logger a user control panel interface. Which, the user can remotely access into the data logger as how the PC does. This method can be enhanced by utilizing the built-in hardware such as global positioning unit (GPS) to retrieve location information, for example to retrieve the data logger coordinate. Mobile Portable Data Logger Data Logger A. Graphic User Interface As shown in Fig. 1 and Fig. 2, user can view real-time data from the data logger through a PC or Tablet. In Windows based PC, monitoring software is developed by using express version of Visual Basic (VB). VB is a third-generation event-driven programming language from Microsoft. The design of VB is to provide users with easy to learn and use environment. The layout of the monitoring software interprets important information form data logger such as real-time graph of the sensed data from each channel with a basic data logger control panel. The details of the software development will be carried out in Section V. Today, two types of mobile operating systems are gaining rapid attention from the markets, and it has occupied almost 85% of the mobile devices sold. They are Android from Google and ios from Apple. In this paper, Android from Google is selected as development platform for Tablet. Google s Android is open-source, which allows developers access to OS source code. Through this advantage, it provides superior customization over others OS. Therefore, developers can develop better software by utilizing system resources. In Section V, we will discuss about the framework of the monitoring software. Smartphone- End User Figure 2. Data logging method (Tablet). B. Real-Time Monitoring Basic data logger is equipped with the external memory storage to log real-time data with date and time stamped. But the external memory has to be removed for data analysis after a period of sensing time. Wireless data logger provides more advantage over cable type data loggers, which it can provide real-time information to the user without the long, expensive and inflexible cable. But the use of wireless transmission may not guarantee the accuracy of the data logger information. A hybrid between wireless communication and external storage provide intelligence solution to the problem, it ensures the data will not be lost in case of communication failure. Fig. 3 shows the hybrid of information delivery method. As shown in Fig. 3, designed data logger has a choice to store the data into external storage module or directly transmit the data through wireless communication module. The use of wireless communication only will be active when the receiver is in the communication coverage. Otherwise the data will be stored into external storage to prepare for next reliable data retrieval. If the receiver is back into communication coverage, the data stored in the external storage will be transmitted to the receiver beginning from the last sent data. PC-End User Data Logger Processing Unit Wireless Communication Module External Storage Module Figure 1. Data logging method (PC). Figure 3. Hybrid of information delivery method /12/$ IEEE 112

3 C. Remote Access Control In practice, the data logger is located at the place where physical accessing to the data logger for software upgrade, calibration and adjustments is time consuming and impractical. Therefore, in this project the designed data logger includes remote access control capability. The terms remote access control means user can wirelessly access into data logger to change the control settings. The operation of the designed wireless data logger consists of two modes, these are active mode and command mode. In the active mode, it includes the operations such as data transmission state and sensing state. While in command mode, user has the authentication to change the data logger settings. If the wireless data logger is in communication coverage, users can remotely access by using Tablet or PC. For example, user can change the data sampling rate in the logger by transmitting a specific command and desired sampling interval time. The modifiable data logger settings include date and time, data sampling rate, channel activation and also data logger basic operation. Each command will be sending into data logger through a pre-designed format, the reason is to avoid data collision. The details of each command will be described in Section V. III. HARDWARE DEVELOPMENT In this Section, hardware development of wireless data logger will be demonstrated. The demonstration is split into two parts, first is the main controller board and followed by the communication modules. Fig. 4 shows the controller diagram of both data logger and mobile portable data logger. The controller consist of 4 basic modules, these are microcontroller unit, wireless communication module, external data storage module and real-time clock module. For ease of development, all the modules are attached to the main microcontroller unit module. Fig. 5 shows the prototype of data logger with tunable potentiometers which acts as sensors. Fig. 6 shows the mobile portable data logger with two types of wireless modules attached in the prototype. The use of different type of wireless modules is to convert data sending from data logger via XBee to the user Tablet via Bluetooth. In this stage, both prototypes can be power up from single 9 V batteries or USB power. Wireless Communication Module Microcontroller Unit Real-Time Clock Module Figure 4. Controller diagram. External Data Storage Module Sensor (potentiometers) XBee XBee Figure 5. Prototype of data logger. Bluetooth Figure 6. Prototype of mobile portable data logger. A. Main Controller Board In the main controller board, the designed board consists of a microcontroller development board, a RTC module and an external data storage module. The main controller board provides data logger a controllable platform, the ability to convert sensor analog signal into digital signal, external memory for data storage and real-time clock. a) Programmable Microcontroller Board: The microcontroller is selected as it provides developer an easy to learn and use platform. It contains everything needed to start a simple project. In this prototype, two microcontrollers are used for both data logger with sensor and mobile portable data logger. Both microcontroller boards are equipped with a 16MHz crystal oscillator and have up to a total of 54 input/output pins and 16 analog inputs. The miniature size and robust build makes the boards durable and flexible for design. b) Real Time Clock (RTC): Is a trickle-charge timekeeping chip that counts seconds, minutes, hours, date of the month, day of the week and year (with leap year) until It is not a good pratice to count time using software counting in the microcontroller. It is hard to ascertain the time taken to execute an instruction due to the clock speed may not be accurate as shown in data sheet. The software has to always active so it keeps the life time counting. Therefore, the use of external RTC chip is very important to imaintain the accuracy /12/$ IEEE 113

4 of the real-time and provides convenience to the software development. Fig. 7 shows the RTC operating circuit used in this paper. The interfaing only requires 3-wire interface. The RTC module is attached with 3 V cell which is connected to VCC1. Secondary power supply guranteed the clock is still running even though there is no power supply to the main controller board. The use of RTC module provides accurate time for the main controller board and also to the sense data. c) External Data Storage (SD card): Is an external data storage that uses to store the sensed data. Since the development board has limited non-volatile memory storage, therefore the design include external memory storage to record large number of data. These prototypes use 2 Gb SD card as external memory for data storage. To access into the SD card, a voltage converter circuit has been developed. It convert 5 V from microcontroller board to 3.3 V use in SD card and vice versa. B. Communication Modules In this project, two types of communication modules have been used. These are XBee wireless module and Bluetooth module. Fig. 8 shows the wireless modules that used in data logger project. Both modules share similar features such as communication protocol, operating voltage and they provide data logger a way to communicate wirelessly. To main board CE I/O SCLK kHz X1 GND X2 V CC1 V CC2 Figure 7. RTC operating circuit. V CC 3V a) XBee Wireless Module: Is the wireless communication module that used for communicating between data logger to PC and also to the mobile portable data logger. The transmission of the XBee module is around 30 m for indoor and 100 m for outdoor. The operating voltage of XBee is 3.3 V, therefore volatge converter circuit has been developed so it can be accessed by main controller. To access into XBee module, UART protocol have been used. The baud rate is set to 9600 and with no parity bit. Since it only use the communication function of XBee, only 4 wires have to connect to XBee module. The description of these 4 pins is shows in Table I. b) Bluetooth Module: Is the wireless communication module that use in communication between mobile portable data logger to Tablet. The transmission range of the module is around 20 m- 30 m which is far enough for the design. Bluetooth BEE wireless module adapts XBee design, which the pinout is compatible with XBee. The operating voltage is same as XBee, voltage converter circuit have been developed so it can be access by main controller board. The communication protocol use in Bluetooth BEE is also the same as XBee, therefore it use the same connection as XBee. IV. HARDWARE DEVELOPMENT After the development of the hardware, simple source code is loaded into the prototypes for hardware verification. The verification scope includes functionality of the development boards, RTC chip and SD card. Simple communication testing has been carried out, there are communication between two XBee modules, the linkage and data transmission between Tablet and development board through Bluetooth BEE. In this Section, software development will be further discussed. It includes the framework of the developed software for main controller board (data logger and mobile portable data logger) and monitoring software (PC and Tablet). A. Data Logger Functionality The data logger is designed to avoid data disruption as the integrity and reliability must be preserved. Fig. 9 shows the basic framework of the data logger. The framework includes the operations of analog-to-digital converter (ADC), data transmission and also data storage into external memory. TABLE I. PIN ASSIGNMENT Symbol Pin Description VIN 1 Power Supply 3.3 V GND 10 Ground DOUT 2 UART Data Out (To Microcontroller) DIN 3 UART Data In (From Microcontroller) Figure 8. Wireless modules /12/$ IEEE 114

5 Start Initialization of Data Logger Retrieve Sensors Value (ADC) Is receiver request data? No Store into External Memory Storage Figure 9. Framework of data logger. In the developed prototype, since few modules are attached to development board, it is important to monitor each module. Time critical modules, such as wireless module provide instant response during the data reception operation. Therefore, it is a must to develop interrupt handle function to avoid data loss when the program is processing other functions. For example, during ADC operation, the operation can be pause so the program can handle interrupt operation from UART. The process continues back to ADC operation after it complete the interrupt operation. RTC module provide real-time to development board, the refreshing rate to obtain real-time from RTC is every 0.25 s interval. After completion of each ADC operation, the output data will be time stamped via directly retrieve from RTC module to acquire accurate time. During the first initialization operation of data logger, a text file will be created to store the sensed data. Fig. 10 shows data log with timestamp recorded in a text file. The format consists of data number, data logger identity (ID), timestamp and data for each channel. Yes Transmit via Wireless Module B. PC End User Application VB has been selected as development platform of PC monitoring software due to its simple to use drag and drop interface. The development of monitoring software starts with the communication between data logger and PC. XBee module will be connected to PC and recognize by PC as serial port. Simple two ways UART communication between XBee is tested using SerialPort class in VB. Fig. 11 shows the PC monitoring software developed by VB. The layout of the monitoring software consists of COM port connection block, control panel block, real-time information graph and data log screen. In the COM port connection block, user can connect to the COM that represents XBee, after the connection is establish which is indicated by the word Online. The data logging process is initiated by pressing the Start button in the control panel. The default sampling rate is 1 s, user can manually change the sampling rate in the control panel. In the real-time information graph at the right hand side of the monitoring software, user can select to view information from each channel. C. Android End User Application Android has been selected as development platform of monitoring software application due to it is open-source and freely available. The development of monitoring software application starts with the communication between mobile portable data logger and Tablet. Communication connection is based on Bluetooth, Tablet built-in Bluetooth and Bluetooth BEE. To provide user a familiar control experience, the design of Android monitoring software is almost same as PC version. Fig. 12 shows the Android application of monitoring software developed by Eclipse. The layout of the monitoring software consists of connection block, control panel block, real-time information graph and data log screen. In the connection block, user can connect to the Bluetooth device that represents mobile portable data logger. Since Bluetooth BEE is used in mobile portable data logger, the default pairing password is After the connection is established, which it is representing by Connected. The data logging process can be initiated by pressing the Start Logging button in the control panel. The control panel provide user to change the data logger settings. The developed Android application also utilizes built-in GPS features to retrieve location coordinate. Figure 10. Data log with timestamp. Figure 11. PC monitoring software /12/$ IEEE 115

6 Figure 12. Android monitoring software. V. CONCLUSION AND FUTURE SCOPE In conclusion, wireless data logger system for real time monitoring has been successfully developed. The developed monitoring software in PC or tablet can view and record realtime information from data logger. In addition, user has authentication to access and change the setting via monitoring software. Data logger with external memory storage can store the sensed data to avoid data lost if the wireless connection is lost. At the time when the receiver is back into communication coverage, the stored data will be transmitted (download) to the receiver. In future, energy consumption of the prototype should be considered. It is a need to develop an energy saving data logger for a longer sensing period. By replacing prototyping integrated circuit with ultra low energy integrated circuit. ACKNOWLEDGMENT The authors would like to acknowledge the financial assistance of the Universiti Malaysia Sabah Research Grant Schemes, grant no. SLB0014-TK-1/2011 and scholarship support by Ministry of Higher Education of Malaysia (MoHE) under MyMaster program. REFERENCES [1] V.I Adamchuka, J.W. Hummelb, M.T. Morganc, S.K. Upadhyayad, "On-the-go soil sensors for precision agriculture," Computer and Electronics in Agriculture, vol. 44, Iss. 1, pp , 2004, doi: dx.doi.org/ /j.compag [2] S. Peets, A. M. Mouazen, K. Blackburn, B. Kuang, and J. Wiebensohn, "Methods and procedures for automatic collection and management of data acquired from on-the-go sensors with application to on-the-go soil sensors," Computers and Electronics in Agriculture, vol. 81, pp , 2012, doi:dx.doi.org/ /j.compag [3] Y.G. Ampatzidisa, M.D. Whitingb, P.A. Scharfa, Q. Zhanga, "Development and evaluation of a novel system for monitoring harvest labor efficiency," Computers and Electonics in Agriculture, vol 88, pp , 2012, doi: dx.doi.org/ /j.compag [4] P. Marino, F.P. Fontan, F. Machado, S. Otero, "Distributed sensors network applied to the rain impairment Study on radiocommunication Systems," IEEE International Conference on Industrial Informatics, pp , 2006, doi: /indin [5] G. Barrenetxea, F. Ingelrest, G. Schaefer, M. Vetterli, O. Couach, M. Parlange, SensorScope: Out-of-the-Box environmental monitoring," International Conference on Information Processing in Sensor Networks, pp , 2008, doi: /ipsn [6] Z.W. Siew, A. Kiring, H.T. Yew, P. Neelakantan and K.T.K. Teo, Energy efficient clustering algorithm in wireless sensor networks using Fuzzy Logic control, Proc IEEE Colloquium on Humanities, Science and Engineering Research, pp , 2011, doi: /chuser [7] Z.W. Siew, C.H. Wong, C.S. Chin, A. Kiring, K.T.K. Teo, Cluster heads distribution of wireless sensor networks via adaptive Particle Swarm Optimization, Proc. 4th International Conference on Computational Intelligence, Communication Systems and Networks, pp , 2012, doi: /CICSyN [8] C.H. Wong, Z.W. Siew, M.K. Tan, R.K.Y. Chin, K.T.K. Teo, Optimization of distributed and collaborative beamforming in wireless sensor networks, Proc. 4th International Conference on Computational Intelligence, Communication Systems and Networks, pp , 2012, doi: /CICSyN [9] R. Grgurina, G. Brestovac, and T.G. Grbac, "Development environment for Android application development: an experience report," Proc. of the 34th International Convention, pp , /12/$ IEEE 116