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An AT89S52 Microcontroller Based Single Board Computer for Teaching an Instrumentation System Course KHAIRURRIJAL MUHAMMAD M MUNIR ASEP SUHENDI HENDRAYANA THAHA MAMAN BUDIMAN Department of Physics Institut Teknologi Bandung Jalan Ganesa 10 Bandung 40132 Indonesia Received 25 July 2005 accepted 2 August 2006 ABSTRACT A single board computer SBC based on the AT89S52 a member of MCS 51 family microcontroller with an ADC serial and parallel communications and input output devices such as a pushbutton a keypad LEDs 7 segment displays and an LCD was developed for teaching an instrumentation system course to the sophomore students Five micro controller related laboratory experiments offered to the students within the 15 week semester are i basic programming of the microcontroller ii interfacing the DIP switches LEDs and 7 segment displays iii application of the analog multiplexer and the ADC with the LCD iv serial communication and application of the HyperTerminal and v measurement of water temperature displaying the measurement result and application of the LabView 2007 Wiley Periodicals Inc Comput Appl Eng Educ 15 166 173 2007 Published online in Wiley InterScience DOI 10 1002 cae 20107 Keywords single board computer SBC AT89S52 MCS 51 microcontroller instrumentation system HyperTerminal LabView Correspondence to Khairurrijal krijal fi itb ac id 2007 Wiley Periodicals Inc 166 INTRODUCTION Microcontrollercourseshavetraditionallybeen taught within electrical engineering departments 1 Mechanicalengineeringdepartmentshavealso recognized the important role of the microcontroller in mechatronic systems 2 Few departments that are neither electrical nor mechanical engineering which offer microcontroller courses in their curricula The Department of Biological and Agricultural Engineering at the University of Georgia USA hasintroductoryandadvancedmicrocontroller courses since biological and agricultural engineers face processes becoming increasingly complex with microcontrollers embedded in them 3 An experi ment using a microcontroller has been tried in the teaching of process control to chemical engineering students at the University of Minnesota Duluth USA 4 and to students in the Department of Applied Physics Electronics and Systems at the University of La Laguna Spain 5 Many physical quantities such as temperature pressure length mass time current and intensity must be measured Most modern instruments used in measuring the quantities include microcontrollers Therefore the development of expertise in micro controllers is also important to physicists In this article we describe an AT89S52 micro controller based single board computer SBC that is used for teaching the instrumentation system course to sophomore students in the Department of Physics at the Institut Teknologi Bandung ITB Indonesia Some laboratory works supporting the course are explained DESCRIPTION OF THE SINGLE BOARD COMPUTER AND ASSOCIATED SOFTWARE PACKAGES For introductory microcontroller courses 8 bit micro controllers are widely utilized because they are simpler to describe easier to use and lower cost than 16 bit or 32 bit microcontrollers Among of the 8 bit microcontrollers the MCS 51 family microc ontrollers were chosen due to its wide spread popu larity especially as an industry standard its simple architecture and the likelihood that they will remain important for years to come 6 In teaching the instrumentation system course to the sophomore students we need a SBC that integrates the MCS 51 microcontroller with light emitting diodes LEDs 7 segment displays a liquid crystal display LCD a pushbutton a keypad and an analog to digital converter ADC so that students who take the course can do laboratory works in a more comfortable way In addition the SBC has the ability toperformserialandparallelcommunications Unfortunately such SBC is not available in the market We therefore decided to design and develop the SBC as shown in Figures 1 and 2 with the features are as follows Figure 1 a Front view of the AT89S52 microcontroller based single board computer SBC with a 220 V AC power supply and cables in the brief case and b enlargement of the SBC Color figure can be viewed in the online issue which is available at www interscience wiley com AN AT89S52 MICROCONTROLLER BASED SBC167 a An AT89S52 8 bit microcontroller 1 with 8 kb of ISP in system programmable fl ash memory ATMEL AT89S52 at http www at The microcontroller is compatible with the industry standard 80C51 instruction set and pinout The on chip flash memory allowstheprogrammemorytobe reprogrammedin system by a personal computer PC In addition the microcon troller provides 256 bytes of random access memory RAM 32 programmable input output I O lines three 16 bit timer counters eight interrupt sources a full duplex serial port and a watchdog timer b Various input and output devices such as an 8 pin dual in line package DIP switches 2 a push button 3 a 4 3 hexadecimal keypad 4 eight LEDs 5 four 7 segment displays 6 and an HD44780 compatible 2 16 alphanumeric LCD 7 The status of the input devices the DIP switches push button and keypad are read and then sent to the microcontroller through the input ports while data from the microcontroller are sent to theoutputdevices LEDsanddisplays through the output ports c A08048 bitmicrocontrollercompatible analog to digital converter ADC 8 National Semiconductor at The conversion type of this ADC is the successive approximation register SAR with the conversion time of 100 ms The ADC appears like memory locations or I O ports to the microcontroller and therefore no interfac ing logic is needed Analog input of the ADC which is in the range of 0 5 V with single 5 V supply can be either two potentiometers 9 or from external connected to the connectors 10 in the board Input selection is done by the CD4051 8 channel analog multiplexer 11 Thepotentiometerssimulateanalog voltage levels to be fed into the multiplexer d A serial communication port that is provided bytheDB9connector 12 Usingthe MAX232 Dallas Semiconductor MAXIM at http www maxim communicate serially with another SBC or a PC e A DB25 parallel communication port 13 for downloading uploading a program onto the microcontroller PC f A power supply input 14 A dc unregulated voltage in the range of 7 12 V can be used g A button for resetting the microcontroller 15 There are two steps that have to be performed to program the AT89S52 microcontroller First a pro gram is created by development software packages on the PC The development software package should include an editor and compiler Many software packages are available for that purposes and some of them are Read51 Rigel Corp Gainesville FL http www and Proview 32 Franklin Software Inc Campbell CA After having edited and compiled the program a hex file is obtained Second the hex file is down loaded into the microcontroller of the SBC by using forinstance theAEC ISP AECElectronics Ltd Christchurch New Zealand http www aec electronics co nz or M Asim Khan s ISP software http chaokhun kmitl ac th kswichit Pgm89v31 web Pgm89v31 html In doing a serial communication between the PC and the SBC the HyperTerminal application Micro soft Corp Redmond WA http www microsoft com under the Microsoft Windows which is ready after having installed the Windows is a good choice because it is easy to use The SBC is also compatible with the LabView under the Microsoft Windows a commercial graph based software from the National Instruments Austin TX that is widely used in industry and instrumentation education With the Figure 2Block diagram of the AT89S52 microcontroller based SBC 168KHAIRURRIJAL ET AL assistance of this software various applications using the SBC become easier and more attractive SOME APPLICATIONS OF THE SBC FOR LABORATORY EXPERIMENTS Measurement is an essential part of the scientifi c processes and the technology of measurement is instrumentation Figure 3 depicts a signal fl ow in the general block diagram of a microcontroller based instrument A sensor is a passive in some cases an active electronic device that converts a physical parameter or variable into an analog electrical signal Since the analog electrical signal is sometimes not in the input range of the ADC the conditioning circuits are needed to adapt the signal The conditioned signal is then converted into a digital signal by the ADC tobe processed by the microcontroller The processed digital signal is fi nally presented by the digital display In the Department of Physics at the ITB the instrumentation system course is a three credit course that meets a 2 h lecture and a 3 h laboratory per week of the 15 week semester The fi rst 3 weeks are to cover basic operational amplifi ers and basic digital devices The next 7 weeks are devoted to the concept and integration of sensors signal amplifi ca tion signal processing data switching data control and data readout The fi nal 5 weeks are reserved for introducing microcontrollers and its role in the instrumentation system Typical course contents are the following Basic operational amplifi ers characteristics basic amplifi ers current to voltage converter bridge amplifi er and instrumentation amplifi er Basic digital devices gates fl ip fl ops and counters Sensors temperature pressure force humidity displacement and electro optics Signal amplifi cation and processing fi lters oscillators modulation demodulation digital to analog and analog to digital conversion and noise and noise reduction Data switching control and readout pulse timers and counters multiplexing and demulti plexing data communication and display Microcontrollers architecture instruction set programming input output ports interrupts timers interfaces with peripheral devices and roles in instruments Based on the course contents and the SBC features many possible experiments are provided by the SBC in which some of them are listed below i Programming the microcontroller ii InterfacingtheDIPswitches LEDs 7 segment displays and LCD iii Interfacing the keypad LEDs 7 segment displays and LCD iv Application of the analog multiplexer and ADC with the 7 segment displays or LCD v Application of the serial communication vi An instrumentation system including physical variable for instance temperature pressure or humidity measurement analog to digital conversion and displaying the measurement results For the 3 h laboratory per week of the 15 week semester the course offers fi ve microcontroller related laboratory experiments a basic program ming of the microcontroller b interfacing the DIP switches LEDs and 7 segment displays c applica tion of the analog multiplexer and the ADC with the LCD d serial communication and e measurement Figure 3Signal flow in the block diagram of a micro controller based instrument AN AT89S52 MICROCONTROLLER BASED SBC169 of water temperature and displaying the measurement result Experiment 1 Basic Programming of the Microcontroller The objectives of the Experiment 1 are to understand the AT89S52 microcontroller architecture and to program the microcontroller In this experiment fi rst the SBC parallel port is connected to the PC printer port Fig 4a Next the development software packages to edit and compile a program as well as to download the program into the SBC Fig 4b are installed into the PC Since a microcontroller is a microprocessor central processing unit with external units like a RAM a read only memory ROM and other support units and it functions to control input output devices as illustrated in Figure 5 created programs in this experiment cover i addressing modes register direct indirect immediate relative absolute and long indexed ii functional modes arithmetic logics boolean data transfer and program branching Experiment 2 Reading From the DIP Switches and Writing to the LEDs and 7 Segment Displays The objectives of this experiment are to read the DIP switches voltage levels logics and to write to the LEDs and 7 segment displays From the functional block diagram given in Figure 6a b it is shown that the inputs the DIP 8 bit switches are sent to port 0 of the microcontroller through the 74LS245 buffer chip By making pin E of the buffer chip to be low the buffer chip is activated and the 8 bit input data reach the microcontroller In order to display the input data port 2 of the microcontroller is connected to the LEDs or the 7 segment displays with the 74LS247 decoder If pin E of the display is high then the input data are displayed In the case of LEDs each bit of the input data is represented by each LED in which if the bit is low high then the LED will turn on off Experiment 3 Application of the Analog Multiplexer and the ADC With the LCD The functional block diagram of the experiment is shown in Figure 7 The objectives of the experiment Figure 4A program is downloaded into the single board computer SBC by using parallel communication Color figure can be viewed in the online issue which is available at Figure 5Functional block diagram of a microcontroller 170KHAIRURRIJAL ET AL are as follows i to read analog voltage inputs IN0 and IN7 stand for potentiometers in the SBC IN1 IN6 are reserved for external inputs which are provided by connectors in the SBC ii to select a channel of the analog multiplexer by pressing a button of the keypad iii to display the selected data input to the LCD If the keypad button is pressed an interrupt request is sent to the microcontroller INT0 and the hexadecimal code reaches port 0 of the microcon troller after enabling the 74LS245 buffer P1 4 After the microcontroller processed the hexadecimal code fi rst 3 bits of port 1 P1 0 P1 2 will send 3 bit control data to the control inputs of the analog multiplexer to select a channel The selected analog input sends its analog voltage to the ADC which is enabled by bit 4 of the port 1 P1 3 The analog voltage is converted into digital data by the ADC The digital data are then received by the microcontroller through the port 0 to be displayed by the LCD which is connected to the port 2 Experiment 4 Application of Serial Communication By using the functional block diagram in Figure 8 the objectives of this experiment are to become familiar Figure 6Block diagram of reading from the DIP switches and writing to a the LEDs and b the 7 segment displays Figure 7Block diagram of application of the analog multiplexer and the ADC with the LCD Figure 8Block diagram of application of serial commu nication in the selection of an input channel and displaying the input data to the LCD AN AT89S52 MICROCONTROLLER BASED SBC171 with the application of serial communication and the HyperTerminal A PC is connected to the SBC through its serial port as shown in Figure 9 The PC sends command data to the microcontroller by using the serial communication The command data ask the microcontroller to select a channel of the analog multiplexer by sending bits of P1 0 P1 1 and P1 2 An input is then selected to send its voltage level to the ADC Next processes follow those explained in the Experiment 3 with the interrupt request of the keypad button is excluded Experiment 5 An Instrumentation System for Temperature Measurement Figure 10a gives an instrumentation system for measuring water temperature with the objectives are as follows i to understand characteristics of the temperature sensors ii to apply the knowledge obtained from the previous experiments to the instrumentation system iii to get accustomed to the LabView as a software for simulation real time measurement and data processing Fig 10b SUMMARY We have designed and developed the SBC integrating the MCS 51 microcontroller with LEDs 7 segment displays an LCD a pushbutton a keypad an ADC serial and parallel communications The SBC is used by the sophomore students of the Department of Physics at the Institut Teknologi Bandung ITB Indonesia who are taking the three credit instru mentation system course to complete their laboratory experiments There are fi ve microcontroller related laboratory experiments which are offered to the students within the 15 week semester The laboratory experiments are i basic programming of the micro controller ii interfacing the DIP switches LEDs and 7 segment displays iii application of the analog multiplexer and the ADC with the LCD iv serial communication and application of the Hyper Terminal and v measurement of water temperature displaying the measurement result and application of the LabView REFERENCES 1 J S Mayer T N Jackson and M E Lockley A new role for microcontroller courses Integrating EE Figure 9Serial communication between the SBC and the PC and the HyperTerminal display Figure 10 a An instrumentation system for measuring temperature of water and b Temperature as a function of time is displayed by using the LabView Color figure can be viewed in the online issue which is available at 172KHAIRURRIJAL ET AL curricula 25th Annual Conference on Frontiers in Education Atlanta GA 1995 Session 3a4 2 M Rabiee Design construction and analysis of a microcontroller system Comput Educ J 6 1996 63 68 3 T K Hamrita Microcontrollers in the biological and agricultural engineering curriculum at the University of Georgia Proceedings of the 2002 American Society for Engineering Education Annual Conference Montreal Canada 2002 Session 1526 4 K B Lodge The programming of a microcontroller as an integral part of process control for undergraduate chemical engineers The 2002 North Midwest Section Annual Conference of the American Society for Engineering Education Madison WI 2002 pp 1 10 5 E J Gonzalez A Hamilton L Moreno R L Marichal and S Torres A set of microprocessor based procedures for an industrial engineering course Comput Appl Eng Educ 12 2004 145 151 6 D Beetner H Pottinger and K Mitchell Laboratories teaching concepts in microcon