Embedded System Laboratory Design using Texas Instruments LaunchPad with Energia

Transcription

1 Embedded System Laboratory Design using Texas Instruments LaunchPad with Energia Sreenivasulu Gummadi Dept. of Humanities & Sciences Malla Reddy Institute of Engineering & Technology Maisammaguda, Secunderabad, India Raghavendra Rao Kanchi Chairman, BOS, VLSI and Embedded Systems Laboratory Dept. of Physics, Sri Krishnadevaraya University Anantapur, India Abstract Rapid advancements in the field of embedded systems, and due to the increase in the usage of embedded controllers in various scientific equipments and day-to-day appliances, it has become essential to focus on advanced course on embedded systems for undergraduate engineering and postgraduate science students in various majors, specifically in computer science, electrical engineering and computer engineering technology. In this paper, we present simple, easy-tolearn, microcontroller based laboratory exercises suitable for a half-semester laboratory course, designed and developed around ultra low-power mixed signal microcontroller: MSP430G2553. This IC comes with a cost-effective mini programming board in a package as: MSP430 LaunchPad, from Texas Instruments, USA. The necessary code for the exercises are developed and compiled using an electronic prototyping platform: Energia, which is based on Arduino and the Wiring frame work, and includes an Integrated Development Environment (IDE) that is based on Processing. All the exercises work in stand-alone mode and can be introduced as take-home experiments. The hands-on experience that one enjoys after completion of these exercises will be useful for students, electronic hobbyists, developers and programmers. Keywords- Embedded system, MSP430G2553, Stand-alone mode, Take-home experiments, Energia, Hands-on experience I. INTRODUCTION Nowadays the application of embedded systems is increasing in diversified fields like: electronics, automobiles, avionics, robotics etc. The complexity of an embedded system can change from product-to-product, depending on the application for which it is meant. Embedded devices are found right from simple products like children toys, microwave ovens up to the satellite control systems. The growing trend in the field of embedded systems and its applications is not only due to advancement in the field of VLSI design but also the development of MEM (Micro Electro-Mechanical) and NEM (Nano Electro-Mechanical) sensors, artificial intelligence and so on, which leads to miniaturization and development of advanced real-time embedded devices. Further, embedded devices have already accounted for 98% of the world s processors in 2003 itself [1]. Thus, in future everything of material significance will be outfitted with a microcontroller. A recent survey estimates that a typical house-hold has hundred processors in its confine [2]. Presently, we are in the third generation of industrial revolution. Advantages of this generation are enjoyed by a common man either directly or indirectly. The impact and presence of embedded systems is felt directly in our walk of life. Further, it is estimated that the application of robotics in industry will undergo exponential growth, becoming a 66 billion dollar industry worldwide by 2025 [3-4]. The continuously growing demand for embedded system engineers calls for training our present engineering and science students for best practices in real-time and embedded system development platforms. Especially, the industry is looking for skilled personnel who have knowledge in the field of computer, electrical and electronics engineering. Thus, the need of the hour is to introduce embedded system training for computer science and computer engineering students also. Keeping the above facts in view point, it is desirable to have a modest approach of introducing laboratory training in hardware to computer science students. In this direction, we have published papers dealing with setting up of laboratory courses using different microcontrollers [5-10]. In this paper, we present a series of experiments for computer science and electrical engineering students. Of course it can also be used for communication engineering. These exercises are designed from scratch and goes up to building up advanced projects. Further, they can be introduced as half-semester laboratory course. All the exercises are built around a low-cost, popular MSP430 LaunchPad from Texas Instruments, USA [11]. This LaunchPad is available on the Indian market at twelve hundred Indian Rupees. The package contains two ultra lowpower mixed signal microcontrollers: MSP430G2553 and MSP430G2452, and a small board for programming and testing. This package with an additional bread board and offthe shelf components are the only requirements for setting up the laboratory. Software is developed using the popular Arduino-like language called: Energia, which is an easy language to learn for freshmen. The software is open source and hence freely downloadable. The cost-effective LaunchPad module, the free software development tool makes

2 it attractive to be introduced as take-home experiments. Student gets 100% benefit of hands-on experience. This paper is organized as follows. Section-II gives a brief overview of the MSP430 architecture. The software development platform using Energia and the programming procedure in a nutshell is described in Section-III. The experimental part is given in Section-IV, and conclusions are given in Section-V. The experimental part is divided in to three modules: Module A, B and C. Module A gives simple input/output (I/O) interfacing. Module B describes the communication experiments and Module C comprises of Project-based experiments. II. ARCHITECTURE DESCRIPTION The Texas Instruments MSP430G2553 is an Ultra-Low- Power Mixed Signal Processor with Von Neumann architecture. It has a powerful 16-bit RISC Processor. The instruction set consists of 51 instructions with three formats and seven addressing modes. The salient features are: Several selectable low-power modes Five power saving modes Choice of selecting clock frequency On-chip peripherals: Timers, Analog-to-Digital Converters, Flash memory, Hardware multiplier, Digital I/O pins, DMA controller, Comparator, USARTs, Watch Dog Timer, Brownout detector, Serial on board programming. Figures 1 and 2 shows the pin configuration and general architecture of MSP430G2553 mixed signal controller [12]. III. SOFTWARE DEVELOPMENT AND PROGRAMMING PROCEDURE In spite of different software development environments supported by TI MSP430G2553, in the present work we chose the Arduino based Energia for software development and programming because of the ease in learning. TI provides various professional and open-source software development environments that include IAR Embedded Workbench, Code Composer Studio (CCS), Rowley CrossWorks, MSP430 Development System, MSP430GCC, Grace for MSP430 and Arduino based Energia, etc [13]. Except Energia the other development environments need the knowledge of embedded C/C++. Energia is based on Wiring and Arduino and uses the Processing IDE. The hardware platform is built around TI MSP430 LaunchPad. A. Energia [14] Energia is an open-source electronic prototyping platform developed by Robert Wessels with the goal to bring the Arduino and Wiring framework to the Texas Instruments(TI) MSP430 LaunchPad evaluation kit. Energia is based on Arduino and the Wiring framework and includes an Integrated Development Environment (IDE) that is based on Processing. The foundation of Energia and Arduino is the Wiring framework that is developed by Hernado Barragan. Energia currently supports several TI devices. The following diagram shows the complete pin map for the LaunchPad MSP430G2553 in Energia. Fig.1. Pin configuration of MSP430G2553 Fig. 3.Pin map for the LaunchPad MSP430G2553 in Energia Key benefits of Energia: Fig. 2. General architecture of MSP430G2x53 Energia enables almost anyone to start easily creating Microcontroller based projects and applications. Its intuitive development window and easy-to-use libraries and functions provide developers of all experience levels to start working more quickly than ever before. Energia cuts much of the traditional, highly-technical details out of development and simplifies the IDE for MCU LaunchPads. This reduces development time and design complexity, making it easy for anyone to program a LaunchPad

3 Together with Energia, LaunchPad can be used to develop interactive objects, taking inputs from a variety of switches or sensors and controlling a variety of lights, motors and other physical outputs. LaunchPad projects can be Stand-Alone or they can communicate with software running on Host PC. B. Procedure to Create a New Sketch Step1: Download Energia from energia.nu site and copy on any drive of the Laptop/Desktop. Step2: Double click Energia.exe file. Energia will start and an empty Sketch window appears. Step3: Select the Serial Port from Tools menu to view available serial ports. Select the COM Port for LaunchPad. Step6: Type in the program and save the sketch with.ino extension. Step7: To compile Fig. and 7. Saving execute the the Sketch Sketch click on File and select Upload or alternatively click on Upload button. Fig. 4. Selecting the COM port for LaunchPad Step4: Select the board LaunchPad MSP430G2553 from Tools menu. Fig. 5. Selecting the LaunchPad MSP430G2553 board Step5: To open new Sketch click on File and select New or alternatively click on New button. The new sketch consists of two functions void setup() and void loop() as shown in the screen shot. Fig. 8. Uploading the File Step8: Now the compiled program is dumped on to the Flash memory of MSP430G2553. The controller is taken out from the IC base of LaunchPad board and used in the standalone mode. IV. DETAILS OF INDIVIDUAL EXPERIMENTS In all the experiments described in the following modules, hex files of the compiled program is dumped on to the flash memory of MSP430G2553.The IC is removed from the LaunchPad board and placed on the bread board in standalone mode. The IC is powered up with +3.3v and the programs are executed. Module A Ex.A1: LED Blink Shift Experiment In this experiment eight LEDs are connected to port P1 pins through current limiting resistors. The output is in negative logic (Port P1 pins are in current sink mode). The schematic diagram is shown in the figure 9. Fig. 6. Creating a new sketch Fig. 9. Schematic diagram for LED blink shift

4 The software is developed basing on the following algorithm: 2. Define LEDs pins on port P1. 3. In void setup() make port P1 pins in output mode. 4. In void loop() make LEDs pins as high. 5. Realize blink shift by using logical shift. The program is kept in continuous loop. Ex.A3: Stepper Motor Interfacing Experiment In this experiment a stepper motor is interfaced using port pins P1.0 to P1.3. As the port outputs of the controller cannot drive the stepper motor directly, the power amplifier ULN2003 [15] is used. It provides the necessary current to drive the motor. The schematic of the connections is shown in the figure 13. Fig. 10. Photograph of LED blink shift Ex.A2: Multiplexing Seven Segment Displays In this experiment four seven segment displays are connected to port P1 pins. Port P2 pins are used to select the digits. The schematic is shown in the figure 11. Fig. 13. Schematic diagram for stepper motor interfacing Program is developed to rotate the stepper motor continuously using the following. 2. In void setup(), set the port pins P1.0 to P1.3 as output. 3. In void loop(), send the data to port pins. 4. Keep on sending the data with delay in between to rotate the motor continuously. Fig. 11. Schematic diagram of seven segment display multiplexing The software to display four digit numbers from 0000 to 9999 in counting mode is developed using the following. 2. Define the segments value of the numbers 0 to 9 to display on each Seven Segment Display. 3. Define the digit position. 4. In void setup() make the ports P1 and P2 pins as output. 5. In void loop() display the number on the Seven Segment Displays. Fig. 14. Photograph of stepper motor interfacing Ex.A4: Push Button Count Display on LCD The main aim of this experiment is to debounce a mechanical switch by software while counting the number of times the button is pressed. The button press count is displayed on LCD interfaced to the controller. Here a 16x2 LCD module is used in 4-bit mode. Port pins P2.0 and P2.1 are used as control pins and pins P2.2 to P2.5 are used to send data. A 10k potentiometer is used for controlling the intensity of the LCD module. The schematic diagram of the connections is shown in the below figure 15. Fig. 12. Photograph of multiplexed seven segment display Fig. 15. Schematic diagram for button press count display

5 . 2. Initialize the LCD. 3. In void setup(), initialize the push button pin. 4. In void loop(), read the button state and count pushes. 5. Display push count on LCD. International Journal of Conceptions on Computing and Information Technology Fig. 16. Photograph showing button press count on LCD Ex.A5: Realization of PWM using LED PWM is a modulation technique that controls the width of the pulse. Its main use is to control the power supplied to electrical devices like bulbs and motors. The MSP430G2553 has two PWM enabled pins P1.0 and P1.6. In present work pin P1.6 is used to realize PWM using LED. The schematic diagram is shown in figure 17. Fig. 18. Jumper positions on header J3 for hardware The program is developed to UART echo back a message string using the following 2. In void setup begin serial communication by selecting the baud rate 9600 bps. 3. In void loop() read the message string and echo back to serial monitor. Figure 19 shows the photograph of serial monitor. Fig. 19. Photograph of serial monitor Fig. 17. Schematic diagram for Realization of PWM using LED.. 2. In void setup(), select the pin mode as high. 3. In void loop(), change the pulse width, apply this pulse to LED to change the intensity. 4. Delay Module B Ex.B1: Serial Communication Experiment Serial communication is used either to control or to receive data from an embedded microprocessor. The MSP430G2553 LaunchPad version 1.5 has two types of serial communications, Hardware UART and Software UART. Hardware UART improves performance over software UART and allows the Arduino serial library to be used. Hardware UART will use less CPU cycles than software UART [energia.nu]. In the present work we chose hardware UART. This is accomplished by manually changing the jumper positions on header J3 to match those shown in figure 18. Ex.B2: Interfacing SPI DAC (MCP4921) SPI is an acronym for Serial Peripheral Interface. It is a synchronous data bus. The data can travel in both directions at the same time. The SPI bus uses four lines MOSI (Master Out Serial In), MISO (Master In Serial Out), SCLK (Serial Clock) and CS (Chip Select). MSP430G2553 has one SPI bus. Pins P1.7, P1.6, P1.5 and P2.0 acts as MOSI, MISO, SCLK and CS respectively. MCP4921 [16] is SPI enabled DAC. CS pin is made Low to High to start SPI communication. The digital data from MSP430G2553 is converted into analog data using MCP4921 and measured with multimeter. The schematic diagram is shown in the figure 20. Fig.20. Schematic diagram for interfacing MCP Include SPI library. 3. In void setup(), begin SPI by setting the bit order as MSB first

6 4. In void loop() make CS low, read data and make CS high. 5. Delay 6. Continue reading the data. International Journal of Conceptions on Computing and Information Technology Fig. 24. Schematic diagram for interfacing Fig. 21. Photograph of interfacing SPI DAC MCP4921 Module C Ex.C1: Measurement of Analog Voltage MSP430G2553 has a 10-bit on-chip analog-to-digital converter (ADC). It has 8-analog input channels. A 10 k potentiometer is connected between +3.3V and Ground. The wiper is connected to analog channel A4. The schematic diagram is shown in the figure Initialize the LCD pins. 3. In void setup() set the LCD to 16x2 display. 4. In void loop() read the sensor signal and convert to temperature in degrees. 5. Display on LCD. Fig. 22. Schematic diagram for the measurement of analog voltage. The software is developed to measure the analog voltage and to display on LCD using the following 2. In void setup(), initialize the LCD in 4-bit mode. 3. In void loop(), read the analog voltage through channel A4 4. Convert the digital output from ADC into analog value. 5. Display on LCD. Fig. 25. Photograph of temperature measurement using LM35 Ex.C3: Measurement of Distance using Ultrasonic Sensor HC-SR04 The sound waves having frequency more than 20 khz are known as Ultrasonic sounds. HC SR-04 [18] produces 40 khz sound waves. Its range is 2 cm to 400 cm and detects whether there is a pulse signal back. Using HC-SR04 we can find the distance of any object or obstacle using Echo principle. It has four pins 1. +5V supply, 2. Trigger pulse input, 3.Echo pulse output, 4. 0V (ground). The schematic diagram of interfacing is shown in the figure 26. Fig.23.Photograph of reading analog voltage on LCD Ex.C2: Interfacing Temperature Sensor LM35 LM35 [17] is an internal signal conditioned temperature sensor. It produces 10mv for every one degree rise in temperature. The LM35 is connected to analog channel A0. The hardware schematic is shown in the figure 24. Fig. 26. Schematic diagram for interfacing HC-SR04 2. Initialize the LCD pins. 3. Define Trigger and Echo pins

7 4. In void setup() set pin modes, Trigger pin to output and Echo pin to input. 5. In void loop(), set Trigger pin to high, Delay, Set Trigger pin to low, Read time duration and convert to distance. 6. Display distance on LCD. V. CONCLUSION In this paper a series of experiments are designed and developed using MSP430G2553 with Energia IDE which is easy to use. These experiments provide hands on experience and can be introduced as take home experiments. Beneficiaries are not only the students but also the hobbyists and developers. Performing these experiments will definitely increase the confidence in the students to think and develop a complex embedded system. REFERENCES Fig.27. Photograph showing HC-SR04 Ex.C4: Measurement of Humidity and Temperature using HSM-20G HSM-20G [19] is a Temperature and Humidity sensor. It has four pins. The analog input channel A0 is connected to humidity pin and the analog input channel A1 is connected to temperature pin. The schematic diagram is shown in the figure 28. Fig.28. Schematic diagram for interfacing HSM-20G. 2. Initialize LCD. 3. In void setup(), initialize sensor pins. 4. In void loop(), read sensor outputs and convert into humidity and temperature values. 5. Display on LCD. Fig. 29.Photograph showing humidity and temperature [1] J.Turley, The two percent solution, embedded system program, Vol.16, no.1, p.29 Jan2003. [2] Mitali Agarwal, Amit Sharma, Pankaj Bhardwaj, Vedpal Singh, A Survey on Impact Of Embedded System on Teaching, MIT International Journal of Electronics and Communication Engineering, Vol.3, No.1, Jan.2013,pp [3] - is - now - on exponential.html. [4] Japan Robotics Association, Tokyo, Japan, The state of the industry world-wide robotics market growth June [5] Aruna Kommu, Raghavendra Rao Kanchi, Varadarajulu R.P.G, Design and development of a low-cost student experiments for teaching ARM based embedded system laboratory, IEEE International Conference on Teaching Assessment and Learning for Engineering (TALE), pp , Aug.26-29,2013. [6] Naveen Kumar Uttarkar, Raghavendra Rao Kanchi, Design and Development of a Low-CostEmbedded System Laboratory Using TI MSP430F149, International Conference on Communication and Signal Processing (ICCSP 13), April 3-5, 2013, India, IEEE Xplore. [7] Swapna Chintakunta, Raghavendra Rao Kanchi, An Embedded system Laboratory Training Using dspic30f6014a, International Journal of Scientific & Engineering Research, Vol.5, Issue 7, July [8] Aruna Kommu, Raghavendra Rao Kanchi, Design and Development of a Low-Cost embedded System Laboratory Using LPC 1768, American Journal of Embedded Systems and Applications, Vol.1, no.2, pp , 2013 [9] Rajeswari Cherukuri, Raghavendra rao Kanchi, Design and development of a project-based embedded system laboratory using PIC 18F25K20, American Journal of Embedded Systems and Applications, Vol.2, no.3, pp , 2014 [10] Swapna Chintakunta, Raghavendra Rao Kanchi, Ramanjappa Thogata. Designing an Introductory FPGA-Based Embedded System Laboratory. American Journal of Embedded Systems and Applications. Vol. 2, No. 2, pp. 6-12, [11] [12] [13] [14] [15] [16] [17] LM35 Precision Centigrade temperature Sensor, Literature Number: SNIS 159B,Texas Instruments, November [18] [19]