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DISPLACEMENT MEASURING USING THE NEW XYZ ACCELEROMETER SENSOR EUROPEAN PROJECT SEMESTER AUTUMN 2010 | INGENIØRHØJSKOLEN I KØBENHAVN Group 6 Student Name Student Number Jorge Pascual Martínez Andrés 101030 Liyue Shen 100931 Lukasz Koczwara 100824 Raquel Abad Carro 100911 Supervisor: Emil Piper Abstract GROUP 6 DISPLACEMENT MEASURING USING XYZ ACCELEROMETER SENSOR Abstract This project outlines the development of a displacement measuring system for walls displacement. It can be also easily adapt to deal with wide range of other types of measurements. The goal of this project is to build a working prototype of a measuring device. The heart of the project is the three-dimensional accelerometer sensor, supported by evaluation board with microcontroller and the LCD display. In general, the system includes physical sensor, signal processing unit and a display. It might also be extended by data acquisition circuit, additional sensors and PC interface with the dedicated software. The system will be built from commercially available components. In this paper the matters of constructing the embedded system, designed to perform presented above function is described. The paper discusses issues of hardware and software layers and project itself, as well as schedule for possible next steps. In the "project status" paragraph actual work which has already been done is presented. This report is written to give the reader an overview over project, as well as, a clear project status and future plans. Table of Contents ii GROUP 6 DISPLACEMENT MEASURING USING XYZ ACCELEROMETER SENSOR Table of Contents Abstract .................................................................... ii Table of Contents ..................................................... iii Table of Images ....................................................... vii List of Tables ............................................................ ix Chapter 1 Introduction .............................................................. 1 Chapter 2 Background of the Project ......................................... 3 2.1 Project Requirements ............................................................ 4 2.2 Operating Parameters ............................................................ 4 2.3 Theorical Basis ....................................................................... 5 2.4 Acceleration ........................................................................... 6 2.5 Gravity ................................................................................... 7 2.5 Coordinate System ................................................................. 7 2.6 Accelerometer Sensor ............................................................ 9 2.7 Analog-to-digital Conversion ............................................... 10 Chapter 3 Field of Use ............................................................. 12 3.1 Seismic Activity .................................................................... 13 3.2 Protection of Hardware ....................................................... 14 3.3 Inertial Navigator System ..................................................... 14 3.4 IPhone Applications ............................................................. 14 3.5 Airbags ................................................................................ 16 3.6 Medical Applications ........................................................... 16 Table of Contents iii GROUP 6 DISPLACEMENT MEASURING USING XYZ ACCELEROMETER SENSOR 3.7 Machine Calibration ............................................................ 17 Chapter 4 Hardware Layer ....................................................... 18 4.1 Overview ............................................................................. 19 4.2 Main Board .......................................................................... 19 4.2 Accelerometer with Evaluation Board .................................. 20 4.3 The Microcontroller ............................................................. 21 4.4 Display ................................................................................. 23 4.5 LD1117 Voltage Regulator .................................................... 24 4.6 RS232 Converter .................................................................. 25 4.7 ADC ..................................................................................... 26 4.8 Multiplexer .......................................................................... 26 4.9 Digital Accelerometer .......................................................... 28 4.10 Constructing the Device ..................................................... 29 4.11 Signals Circuit .................................................................... 30 Chapter 5 Programming Using AVR Studio 4 ............................ 32 5.1 Software Overview .............................................................. 33 5.2 Create a New Project ........................................................... 34 5.3 C Language Project Management ......................................... 35 5.3.1 View c files and header files in explorer window ............................... 35 5.3.2 Add external library to the project ..................................................... 37 5.4 Compile and Build ................................................................ 38 5.4.1 Overview .......................................................................................... 38 5.4.2 Compile and find errors in the codes ................................................. 39 5.4.3 Build and make a .hex file ................................................................. 39 5.5 Debug and Simulate ............................................................. 40 5.5.1 Debug tools in AVR Studio ................................................................. 40 5.5.2 Simplest and most powerful debug way ............................................ 44 5.6 Programming and Settings ................................................... 45 5.6.1 Overview .......................................................................................... 45 5.6.2 Connect the target device.................................................................. 45 5.6.3 Programming setting ......................................................................... 46 5.6.3.1 Main tab ................................................................................. 46 5.6.3.2 Program tab ............................................................................ 48 Table of Contents iv GROUP 6 DISPLACEMENT MEASURING USING XYZ ACCELEROMETER SENSOR 5.6.3.3 Fuses tab ................................................................................ 49 Chapter 6 Design and Implementation of Embedded Software 51 6.1 On-chip Software Overview ................................................. 52 6.2 Functions of Current Version .............................................. 52 6.3 Implementation of Current Version .................................... 53 6.3.1 Overview .......................................................................................... 53 6.3.2 Receive Data from Accelerometer Sensor .......................................... 53 6.3.3 Analog-to-digital Conversion (ADC) ................................................... 54 6.3.3.1 Introduction of ADC ................................................................ 54 6.3.3.2 Reason to do ADC ................................................................... 55 6.3.3.3 ADC method and settings ........................................................ 60 6.3.3.4 ADC rule and result format ...................................................... 63 6.3.4 Get Acceleration from Digital Numbers (ADC Results) ........................ 63 6.3.4.1 Overview and problems to solve ............................................. 63 6.3.4.2 ADC result collection and calibration ....................................... 64 6.3.4.3 Sampling ................................................................................ 65 6.3.4.4 Get acceleration from ADC result ............................................ 66 6.3.4.5 Remove gravity factor from acceleration ................................. 67 6.3.4.6 Algorithms gathering and optimize ......................................... 68 6.3.5 Calculate Displacement from Acceleration and Time .......................... 70 6.3.5.1 Overview and formula introduction ........................................ 70 6.3.5.2 Mathematical algorithm ......................................................... 71 6.3.5.3 Program algorithm .................................................................. 72 6.3.6 Use LCD as a Display Component ....................................................... 74 6.3.6.1 Reason to choose LCD ............................................................. 74 6.3.6.2 LCD using method and output result ....................................... 74 6.3.7 Communicate with PC Through Serial Port ......................................... 76 6.3.7.1 Overview ................................................................................ 76 6.3.7.2 UASRT register usage and setting ............................................ 76 6.3.7.3 Data transfer protocol ............................................................. 81 6.3.8 CPU Clock Frequency Setting ............................................................. 82 6.3.8.1 Overview ................................................................................ 82 6.3.8.2 Clock setting ........................................................................... 82 6.3.9 Using the TIMER0 to Get Time ........................................................... 83 6.3.9.1 Overview ................................................................................ 83 6.3.9.2 TIMER0 operating theory ........................................................ 83 6.3.9.3 Get time from the TIMER0 ...................................................... 85 6.3.10 Precision Statement and Error Reducing .......................................... 87 6.3.10.1 Algorithm precision statement .............................................. 87 6.3.10.2 Error reducing ....................................................................... 88 Table of Contents v GROUP 6 DISPLACEMENT MEASURING USING XYZ ACCELEROMETER SENSOR Chapter 7 Design and Implementation of the PC Display Software ......................................................................... 90 7.1 PC Display Software Overview ............................................. 91 7.2 Functions of PC Display Software and User Guide ................ 91 7.3 Implementation of Current Version .................................... 94 Chapter 8 Structure and Management of the Project ............... 97 8.1 Overview ............................................................................. 98 8.2 Managing the Project. ......................................................... 98 8.2.1 Work Breakdown Structure (WBS) ..................................................... 98 8.2.1.1 WBS overview ........................................................................ 98 8.2.1.2 Research branch ................................................................... 100 8.2.1.3 Assembly Branch .................................................................. 100 8.2.1.4 Programming Branch ............................................................ 100 8.2.2 Gantt Chart ..................................................................................... 101 8.2.3 Responsibility Matrix (RM) .............................................................. 103 8.3 Checking the Progress Process ........................................... 104 8.4 Dealing with Problems ....................................................... 104 8.4.1 Overview ........................................................................................ 104 8.4.2 Troubles Section .............................................................................. 104 8.4.2.1 Misunderstanding – STK502 .................................................. 104 8.4.2.2 Power ................................................................................... 105 8.4.2.3 Wires .................................................................................... 105 8.4.2.4 Multiplexer(MUX) ................................................................. 106 8.4.2.5 Crystal .................................................................................. 106 8.4.2.6 Plan changes ......................................................................... 107 8.4 Status at Project Review 2 ................................................. 108 8.4.1 New Gantt Chart - Project Review 2 ................................................. 108 8.4.2 Status of Work Breakdown Structure - Project Review 2 .................. 109 8.4.3 Status of Responsibility Matrix - Project Review 2 ............................ 110 Chapter 9 Future Work .......................................................... 111 9.1 Overview ........................................................................... 112 9.2 Memory Storage ................................................................ 112 Table of Contents vi GROUP 6 DISPLACEMENT MEASURING USING XYZ ACCELEROMETER SENSOR 9.3 Display ............................................................................... 112 9.4 Wireless Communication ................................................... 113 9.5 External Power Unit ........................................................... 113 9.6 MUX + Other Accelerometers ............................................ 113 9.7 Noise Issues ....................................................................... 114 Chapter 10 Conclusion ............................................................ 115 Chapter 11 References ............................................................ 117 Chapter 12 Glossary ................................................................ 120 Chapter 13 Appendix ............................................................... 124 13.1 Quick Start Tutorial .......................................................... 125 13.1.1 Tutorial Overview .......................................................................... 125 13.1.2 Components ................................................................................. 126 13.1.2 Assembly ...................................................................................... 126 13.1.3 PC Connection. .............................................................................. 129 13.2 Loogbook ........................................................................ 132 Table of Images vii GROUP 6 DISPLACEMENT MEASURING USING XYZ ACCELEROMETER SENSOR Table of Images Fig. 2.1: Cartesian coordinate system. ................................................................................ 8 Fig. 2.2: Distance of a point. ................................................................................................ 8 Fig. 2.3: Distance between two points. ............................................................................... 9 Fig. 2.4: Accelerometer. ....................................................................................................... 9 Fig. 2.5: Conversion analog - digital. .................................................................................. 10 Fig. 2.6: Conversion of successive approximation............................................................. 11 Fig. 3.1: QCN Logo. ............................................................................................................ 13 Fig. 3.2: Rolando game. ..................................................................................................... 15 Fig. 4.1: Main Board. .......................................................................................................... 19 Fig.4.2: Accelerometer with evaluation board. ................................................................. 21 Fig. 4.3: Microcontroller ATMega16. ................................................................................. 22 Fig. 4.4: LCD Display. .......................................................................................................... 23 Fig. 4.5: LD1117 Voltage regulator. ................................................................................... 24 Fig. 4.6: RS232 USB Converter. .......................................................................................... 25 Fig. 4.7: Multiplexer. .......................................................................................................... 26 Fig. 4.8: 2 to 1 Multiplexer................................................................................................. 28 Fig. 4.9: Accelerometer sensor ADXL345Z......................................................................... 28 Fig. 5.1 AVR Logo ............................................................................................................... 33 Fig. 5.2 ............................................................................................................................... 34 Fig. 5.3 ............................................................................................................................... 34 Fig. 5.4 ............................................................................................................................... 35 Fig. 5.5 ............................................................................................................................... 36 Fig. 5.6 ............................................................................................................................... 37 Fig. 5.7 ............................................................................................................................... 37 Fig. 5.8 ............................................................................................................................... 38 Fig. 5.9 ............................................................................................................................... 38 Fig. 5.10 ............................................................................................................................. 39 Fig. 5.11 ............................................................................................................................. 39 Fig. 5.12 ............................................................................................................................. 40 Fig. 5.13 ............................................................................................................................. 41 Fig. 5.14 ............................................................................................................................. 42 Fig. 5.15 ............................................................................................................................. 43 Fig. 5.16 ............................................................................................................................. 43 Fig. 5.17 ............................................................................................................................. 45 Fig. 5.18 ............................................................................................................................. 46 Fig. 5.19 ............................................................................................................................. 47 Fig. 5.20 ............................................................................................................................. 48 Fig. 5.21 ............................................................................................................................. 49 Fig. 5.22 ............................................................................................................................. 50 Fig. 5.23 ............................................................................................................................. 50 Fig. 6.1 ............................................................................................................................... 55 Fig. 6.2 ............................................................................................................................... 56 Fig. 6.3 ............................................................................................................................... 57 Table of Images viii GROUP 6 DISPLACEMENT MEASURING USING XYZ ACCELEROMETER SENSOR Fig. 6.4 ............................................................................................................................... 57 Fig. 6.5 ............................................................................................................................... 58 Fig. 6.6 ............................................................................................................................... 59 Fig. 6.7 ............................................................................................................................... 59 Fig. 6.8 ............................................................................................................................... 65 Fig. 6.9 ............................................................................................................................... 69 Fig. 6.10 ............................................................................................................................. 70 Fig. 6.11 ............................................................................................................................. 75 Fig. 6.12 ............................................................................................................................. 83 Fig. 7.1 ............................................................................................................................... 92 Fig. 7.2 ............................................................................................................................... 92 Fig. 7.3 ............................................................................................................................... 93 Fig. 7.4 ............................................................................................................................... 94 Fig. 7.5 ............................................................................................................................... 95 Fig. 8.1 – Work Breakdown Structure ............................................................................... 99 Fig. 8.2 - Gantt chart ........................................................................................................102 Fig. 8.3 – Responsibility Matrix ........................................................................................103 Fig. 8.4 – Gantt chart, Project Review 2 ..........................................................................108 Fig. 8.5 – Work Breakdown Structure, Project Review 2 ................................................109 Fig. 8.6 – Responsibility matrix, Project Review 2 ...........................................................110 Fig. 1: Headers description. ............................................................................................125 Fig. 2: Components. ........................................................................................................126 Fig 3:Default jumpers. ....................................................................................................127 Fig 4:STK500 - ISP mode. ................................................................................................127 Fig 5:LCD to ATmega16. ..................................................................................................128 Fig 6:Potentiometers. .....................................................................................................128 Fig 7:LD1117 connection. ...............................................................................................128 Fig 8:Crystal on the board...............................................................................................129 Fig 9:External crystal jumpers setting. ...........................................................................129 Fig. 10: RS232 pins on the board. ....................................................................................129 Fig. 11: RS232 Spare port ................................................................................................130 Fig. 11: Circuit overview ..................................................................................................131 Background of the Project 6 GROUP 6 DISPLACEMENT MEASURING USING XYZ ACCELEROMETER SENSOR Distance is a one-dimensional quantity and the standard unit is the meter (m). However, this displacement may be only a few tenths of a millimeter or even thousands of kilometers. 2.4 Acceleration The acceleration is a measure of how rapidly the velocity is changing [2]. To calculate acceleration it is necessary to know the speed and elapsed time. Two types of acceleration can be differentiated. On the one hand, average acceleration is obtained during a period of time. ܽ ௫ ≡ݒ ௫௙ −ݒ ௫௜ ݐ ௙ −ݐ ௜ = ∆ݒ ௫ ∆ݐ Units, used to express acceleration, are meters per second (m/s 2 ). To remember that speed is expressed as: ݒ ௫ = ∆ݔ ௫ ∆ݐ On the other hand, it is possible to calculate the instantaneous acceleration. It is useful when the average acceleration changes in the different intervals of time. It is calculated with the equation presented below: ܽ ௫ ≡ lim ∆௧→଴ ∆ݒ ௫ ∆ݐ=݀ݒ ௫ ݀ݐ When the acceleration is positive, it means that the direction is x positive, so acceleration is in the same direction that earth’s gravity. If otherwise the acceleration is negative, it means that the direction is x negative. Background of the Project 7 GROUP 6 DISPLACEMENT MEASURING USING XYZ ACCELEROMETER SENSOR 2.5 Gravity Newton’s law of universal gravitation says: "Every particle of matter in the universe attracts every other particle with a force that is directly proportional to the product of the masses of the particles and inversely proportional to the square of the distance between them" [1] If it is translated into an equation: ܨ ௚ =ܩ·݉ ଵ ·݉ ଶ ݎ ଶ This constant of proportionality is G=6.67x10 -11 N·m 2 ·kg -2. To calculate acceleration, the acceleration due to gravity at the earth’s surface must be taken into account. It is calculated by: ݃=ܩ·݉ ா ܴ ா ଶ mE: Earth’s mass. RE: Earth’s radius. 2.5 Coordinate System The most common system is Cartesian coordinates. It consists of three perpendicular axes. The same scale is used for each one. The horizontal plane corresponds to x-axis and y-axis and the vertical axis is called z-axis. [2] Background of the Project 8 GROUP 6 DISPLACEMENT MEASURING USING XYZ ACCELEROMETER SENSOR Fig. 2.1: Cartesian coordinate system. A point in the space is defined with three numbers. The first number is to indicate the displacement by x-axis, the second one to indicate displacement by y-axis and the last one is to indicate displacement by z-axis. The distance (modulus) between that point and the coordinates’ center is calculated using: ݀=ඥݔ ଶ +ݕ ଶ +ݖ ଶ Fig. 2.2: Distance of a point. The distance between two points that are not the coordinates’ center is calculated as the difference between their modulus. Background of the Project 9 GROUP 6 DISPLACEMENT MEASURING USING XYZ ACCELEROMETER SENSOR  ௧ = ଶ − ଵ Fig. 2.3: Distance between two points. 2.6 Accelerometer Sensor An accelerometer sensor is basically a seismic mass inside a case. A dashpot is used to absorb the movement between the mass and the case. That movement is proportional to the acceleration. A variable resistor is used to convert the vibration into voltage. Because of inertia, the seismic mass is always moving, that is its natural frequency. Since this frequency, it is considered that the sensor is really moving. The seismic mass is surrounded with a coil and is made with a magnet. [3] Fig. 2.4: Accelerometer. Background of the Project 10 GROUP 6 DISPLACEMENT MEASURING USING XYZ ACCELEROMETER SENSOR Accelerometers are used to detect very small vibration in stationary and mobile devices. They internally generate an output voltage proportional to g’s (100mV/gcommon reference value). After the accelerometer output signal is received by the measurement instrumentation, the acceleration is converted to either velocity or displacement.[11] Other type of accelerometer is made with piezoelectric crystals. They are small and with a very high natural frequency. Main disadvantage is that the mass influence on the result of nonlinearity and bias. [4] 2.7 Analog-to-digital Conversion When it is working with physical quantities, continuous values are used. By continuous is meant that the quantity can take any value between two extremes. However, computers and some electronics devices are working with digital values. An ACD converts an input voltage (analog domain) into a number (digital domain). Fig. 2.5: Conversion analog - digital. Background of the Project 11 GROUP 6 DISPLACEMENT MEASURING USING XYZ ACCELEROMETER SENSOR If analog data is using, some information can be lost because the noise and interferences in the wire and electronics. But, using digital data those problems disappear. Two groups of conversion techniques exist to convert analog values into digital values. One of them is comparing the analog signal with a reference voltage. The other is to change the analog signal in time or frequency and compare these values with others already known. In the case of this project the conversion is very easy to make. The power used is between 0V and 5V and the resolution is between 0 and 1023. With these parameters, the conversion is:   5=  1023 The converter uses the method of successive approximation. With this method the first step is to compare the analog value with the value of half full scale range (V FSR /2). If the input signal is higher, the next step is to compare with 3V FSR /4. If the input signal is lower is compared with V FSR /4. During the next steps the signal is compared with the next half value higher or lower. Its advantages are the speed to convert and the process is independent of the analog value. Fig. 2.6: Conversion of successive approximation. 12 GROUP 6 DISPLACEMENT MEASURING USING XYZ ACCELEROMETER SENSOR Chapter 3 Field of Use Field of Use 13 GROUP 6 DISPLACEMENT MEASURING USING XYZ ACCELEROMETER SENSOR 3.1 Seismic Activity ’Quake-Catcher Network’ It is an initiative to detect and to study earthquakes. The idea is to use the sensors which are inside people laptops to detect seismic activity. Volunteers’ CPU are used to analyze the signals and, if seismic movement is detected, to send a warning to SETI center. Also desktop computers are suitable. A universal serial bus accelerometer can be connected to become part of the network. This option is even better. Many aspects proof that theory. Desktop computer usually stands on its place without moving and they are frequently placed on the floor. That reason is fair enough to choose desktop stations. Fig. 3.1: QCN Logo. Field of Use 14 GROUP 6 DISPLACEMENT MEASURING USING XYZ ACCELEROMETER SENSOR 3.2 Protection of Hardware ’The ThinkPad APS Accelerometer Interface’ This IBM’s application is designed to detect when a laptop is falling or shaking with risk for the hard drive. When risk is detected the hard disk its disconnected to avoid the damage and possible data lost. The accelerometers used to detect potential harmful movement are placed on the motherboard; these sensors are gathering data about displacement each 5 microsecond. 3.3 Inertial Navigator System This is a system that can control the speed and position of a moving vehicle in order to steer or redirect the object. The Inertial Navigator System controls present position, orientation and speed using gravitational field, initial position, initial speed and initial orientation relative to a coordinate system. Accelerometers and gyroscopes are used to obtain the data. It is very useful for guiding missiles, aircraft, ships, spacecraft and submarines. 3.4 IPhone Applications Iphone maximizes the accelerometer’s use with a lot of applications. Here, only some examples are presented, but there are many more. What is more, it is still possible to create others and find many new ways to work with accelerometers in smart phones. Field of Use 15 GROUP 6 DISPLACEMENT MEASURING USING XYZ ACCELEROMETER SENSOR IWalk, Pedometer and iSteps Distance are designed to count the steps and calculate the distance walked. Fig. 3.2: Rolando game. Rolando is one of the best games (currently) using accelerometers. The initial tilt controls are one of the hardest parts to program when a game is being designed. Because of that, some developers do not think about this requirement and the game does not work correctly. In other words, if the initial tilt controls are not programmed, the game thinks that the device starts always in the same position. Some applications are used as a remote control, for example TouchOSC and Lego Mindstorm App. Moreover, these applications need other electronic support and software support. For example an Arduino board. Arduino is an open-source electronics prototyping platform based on flexible, easy-to-use hardware and software. [12] Hardware Layer 22 GROUP 6 DISPLACEMENT MEASURING USING XYZ ACCELEROMETER SENSOR The microcontroller used is ATmega16. It is a low-power CMOS 8-bit microcontroller based on the AVR enhanced RISC architecture. By executing powerful instructions in a single clock cycle, the ATmega16 achieves throughputs approaching 1 MIPS per MHz allowing the system designed to optimize power consumption versus processing speed. [8] Fig. 4.3: Microcontroller ATMega16. Technical/Catalog Information ATMEGA 16/16PI Vendor Atmel Category Integrated Circuits (ICs) Program Memory Size 16KB (16K x 8) RAM Size 1K x 8 Number of I/O 32 Package / Case 40 - DIP(600 mil) Spee d 16MHz Oscillator Type Internal Packaging Tube Program Memory Type FLASH EEPROM Size 512 x 8 Core Processor AVR Data Converters A/D 8x10b Core Size 8 - Bit Operating Temperature - 40°C 85°C Connectivity I2C, SPI, UART/USART Peripherals Brown - out De tect/Reset, POR, PWM, WDT Voltage - Supply (Vcc/Vdd) 4.5V 5.5V Lead Free Status Contains Lead RoHS Status RoHS Non - Compliant Table 4.2: ATMega16 brief specification Hardware Layer 23 GROUP 6 DISPLACEMENT MEASURING USING XYZ ACCELEROMETER SENSOR This microcontroller was chosen because it satisfies the project requirements as well as supporting system development tools like C compilers, macro assemblers, program debugger/simulators, in-circuit emulators, and evaluation kits. 4.4 Display This display (MC1602C8-SYL, LCD MODULE, ALPHANUMERIC, 2x16, FARNELL) is an excellent solution for displaying text messages where a low profile is required as in handheld and mobile devices. Fig. 4.4: LCD Display. The display uses the microcontroller Hitachi HD44780U. This 80 pins microcontroller is a special dot matrix LCD driver controller with low power consumption (2.7 to 5.5V) and able to use 4-bit data or 8-bit data interface. Moreover, it has a wide range of instruction function like: display clear, cursor home, display on/off, cursor on/off, display character blink, cursor shift and display shift. It contains an internal oscillator with external resistors and an automatic reset circuit that initializes the controller/driver after power on. Hardware Layer 24 GROUP 6 DISPLACEMENT MEASURING USING XYZ ACCELEROMETER SENSOR The reason for choosing 2x16 standard display is very simple. While building a prototype, only one accelerometer was used, and the second one was simulated using potentiometers. While working with two accelerometers we need nothing more but two lines with 16 characters each to display the results. Nowadays it is all about the cost so the choice was very simply. Another advantage is that the display is the most popular one, supported with many additional libraries and written by amateurs, ready to use, functions. 4.5 LD1117 Voltage Regulator Fig. 4.5: LD1117 Voltage regulator. In the project an LD1117 voltage regulator is being used. The LD1117 is a low drop voltage regulator able to provide up to 800mA of Output Current, available even in adjustable version (Vref=1.25V). Concerning fixed versions are offered the following Output Voltages: 1.2V, 1.8V, 2.5V, 2.85V, 3.0V, 3.3V and 5.0V. The 2.85 type is ideal for SCSI-2 lines active termination. The adjustable LD1117 is pin to pin compatible with the Hardware Layer 25 GROUP 6 DISPLACEMENT MEASURING USING XYZ ACCELEROMETER SENSOR other standard. Adjustable voltage regulators maintaining the better performances in terms of Drop and Tolerance. [9] It was chosen because the accelerometer needs 3.3V and the board only offers 5V. 4.6 RS232 Converter Fig. 4.6: RS232 USB Converter. To program the board it is more useful to work with laptops than desktop stations. The modern laptops do not have RS232 connector. For that reason, the project needs a RS232 converter to USB. The converter is not only a wire. It needs electronics and drivers to adapt both exits. RS232 is for serial communication and only defines the interface layer. The application layer must be written for specific software. USB is a bus system and more than one peripheral can be connected at the same time. The standard describes the physical layer and the protocols. To connect USB to RS232 is necessary to emulate a RS232 UART in the USB part. Hardware Layer 26 GROUP 6 DISPLACEMENT MEASURING USING XYZ ACCELEROMETER SENSOR RS232 ports work with three power sources: +5V for the UART logic, and -12V and +12V for the output drivers. In the USB case, only +5V is necessary. Some converters use AC/DC converters to provide the right voltages. 4.7 ADC The ADC is the analog-digital converter. The ADC used in the project was integrated in the microcontroller. It uses 10-bit of resolution. The inputs are: 8 Multiplexed Single Ended Input Channels, 7 Differential Input Channels and 2 Differential Input Channels with Optional Gain of 10x and 200x. The Input Voltage Range is between 0 and Vcc. The method used to convert is successive approximation. 4.8 Multiplexer Fig. 4.7: Multiplexer. Multiplexer does not appear in the actual prototype, but is the next step if it is wanted to add more accelerometers. Hardware Layer 27 GROUP 6 DISPLACEMENT MEASURING USING XYZ ACCELEROMETER SENSOR A multiplexer is a combinational circuit with n (usually power of two) inputs and one output. Showed output is the value found in the selected input. In a digital multiplexer with 2 n inputs, there are n control signals to decide which input is wanted to show in the output. The Boolean equation that describes this operation in a 2-to-1 multiplexer is: =·+ (·) Also it can be expressed using a truth table: C X Y Z 0 0 0 0 0 1 0 1 0 1 1 1 1 1 0 0 0 0 1 1 1 0 0 1 1 1 Table 4.3: Multiplexer truth table. Hardware Layer 28 GROUP 6 DISPLACEMENT MEASURING USING XYZ ACCELEROMETER SENSOR Fig. 4.8: 2 to 1 Multiplexer. 4.9 Digital Accelerometer Fig. 4.9: Accelerometer sensor ADXL345Z. Other of the immediate steps is to change the analog accelerometer with digital accelerometer. In this case, it was studied the ADXL345 Digital Accelerometer. The ADXL345 is a small, thin, ultralow power, 3-axis accelerometer with high resolution (13-bit) measurement at up to ±16 g. Digital output data is formatted as 16-bit twos complement and is accessible through either a SPI (3- or 4-wire) or I2C digital interface. [10] Hardware Layer 29 GROUP 6 DISPLACEMENT MEASURING USING XYZ ACCELEROMETER SENSOR 4.10 Constructing the Device First step is to collect all of the components. According to data sheets and documentation, power issues should be considered before assembly process. If any power conversion is required, additional devices such as voltage level converters should be added. Next step is to consider the signal path in the circuit in order to predict any noise errors or signal distortion. If needed, low passing filter should be implemented either in software or hardware layer. Additional capacitors and resistor as well as regulators like potentiometers should be considered. After research and brainstorming process, assembly steps should be followed with manual work. Pin to pin wires are essential to connect components. At least 20 wires should be prepared. It is a good idea to solder pin headers to LCD component and analog accelerometer in order to simplify access to connectors. While connecting the devices a good habit is first to connect GND pin, and then Vss or any other power pin. This will prevent component from power shock if power on the board will be present. Many components request GND connection. In order to decrease number of wires, common ground wire can be constructed. The same idea applies to power supply pins. While working with the board and devices like external crystals jumper settings should be checked. Hardware Layer 30 GROUP 6 DISPLACEMENT MEASURING USING XYZ ACCELEROMETER SENSOR In the above paragraph only general matters were considered. Assembling the device from separate components is described in the “Quick Start” tutorial included in the appendix. 4.11 Signals Circuit The beginning of the signal path is in the accelerometer. Analog accelerometers generate level of voltage as their output. Level can differ from 0V to 3.3V (for power supply of 3.3V).Due to earth’s gravity appropriate analog signal is being sent to microprocessor. To be more specific the signal is send to PORTA of the ATmega16 unit, which is supported with internal ADC converters. Resolution of the on-chip ADC peripheral is 10 bits. That means we can receive a number form 0 up to 1023 (2^10). As a reference value 5V was used, so numbers around 1000 will never be reached. Because 5V of output stands for number 1023, and accelerometer can generate 3.3V at most. This analog signal is converted to the digital one and sent to LCD display as an integer numbers, as well as, to the PC via RS232 protocol, also as a set of integer numbers. Digital signal is processed on the PC. That means signal is analyzed and visualize as a chart or graph. Exactly the same process refers to simulated with potentiometers accelerometer. Important matter is voltage level conversion realized by LD1117 regulator. It is done in order to provide required amount of power to the accelerometer. Whole process of generating output signals and converting them in repeated in infinitive loop. Hardware Layer 31 GROUP 6 DISPLACEMENT MEASURING USING XYZ ACCELEROMETER SENSOR A pragmatic strategy to get familiar with a new device is to hook it up and see what data it delivers. That is how data was analyzed and divided into positive and negative value for each axis. During this chapter, it has been explaining the used components and why they were chosen. The most important reasons were versatility, easy use and low power. Also some proposals for new devices are described. Programming Using AVR Studio 4 38 GROUP 6 DISPLACEMENT MEASURING USING XYZ ACCELEROMETER SENSOR Then go back to the AVR Studio window, look at the explorer window, right click on the “Source Files” folder. In the right click menu, click the first option “Add Existing Source File(s)”. In the next window, choose the .c file copy under the AVR project folder. And it is more or less the same to right click the “Header Files” button to add a .h file to the project. Fig. 5.8 Now, the external LCD library is completely under the current AVR project’s folder. Use C language to include the .h file in the main .c file and enjoy the use of them. 5.4 Compile and Build 5.4.1 Overview Compile and build are basic programming procedures making the .c and .h files to machine language. To compile and build the program, click the “Build” option on the menu bar and choose kinds of commands. Or, press Alt+F7 for compile and F7 is for build. Fig. 5.9 Programming Using AVR Studio 4 39 GROUP 6 DISPLACEMENT MEASURING USING XYZ ACCELEROMETER SENSOR 5.4.2 Compile and find errors in the codes Compiling is also a way to check the grammar of the codes. If there is any error or warning in the program, user will be informed by AVR Studio in the “Build” information window. Click the line with colored point to track the places of errors or warnings. Fig. 5.10 Correct these mistakes until there is no error after compiling. Compared with errors, warnings are lower level mistakes that will not influence the executing of the program. Build will succeed with warnings in compiling. However, warnings always imply potential insecurity. Fig. 5.11 5.4.3 Build and make a .hex file The build command will first compile the program, and make a .hex file under user’s AVR project folder after a successful compiling. This file is written in hexadecimal, Programming Using AVR Studio 4 40 GROUP 6 DISPLACEMENT MEASURING USING XYZ ACCELEROMETER SENSOR and can be recognized by the micro controller. All the functions implemented in .c files and .h files are translated into this kind of code and will be carried out by the device after programming the HEX file into the device. [For how to program the device, see Chapter 5.6 Programming and settings] Fig. 5.12 If the code (.c files or .h files) is changed, a build command is needed for saving these changes and updating the HEX file. 5.5 Debug and Simulate 5.5.1 Debug tools in AVR Studio AVR Studio provides debug tools and the debugging can be done in a simulated way, which means, when running the program, AVR Studio will simulate the behavior of memory and register using the computer’s memory without physically connecting the micro controller and accessing its physical memory. Programming Using AVR Studio 4 41 GROUP 6 DISPLACEMENT MEASURING USING XYZ ACCELEROMETER SENSOR The simulating is only valid to the standard memory positions and standard data registers, which means AVR Studio cannot simulate the memory behavior of external electronic components. Because AVR Studio will never know what is connected to the developing board. All it recognizes is the micro controller (ATmega16)’s ports and pins, which are regarded as the interface between external electronic components and the micro controller. Since debug tools in AVR Studio are very powerful, and time is limited searching for all the usages, this part will only introduce some most easy and commonly used functions. In fact, these very basic debug functions are already enough for us to test the program. To start debugging, click “Debug” button on the menu bar, choose “Start Debugging”. Then AVR Studio will run the program in debugging mode. Fig. 5.13 Programming Using AVR Studio 4 42 GROUP 6 DISPLACEMENT MEASURING USING XYZ ACCELEROMETER SENSOR Under debugging mode, there will be many external menu and windows. Above the main menu bar, there is a debugging menu bar with some commonly used buttons about debugging, which can also be found in the menu above. Fig. 5.14 From left to right, buttons and functions are as following: • Start: to start debugging. • Stop: to stop debugging and quit debugging mode. • Run: to run the program until break. • Break: to break the running of program. • Reset: to restart debugging. Buttons from the yellow pointer to the text icon with blue pointer are different step types. Step type means the way to go through the code. Since there are several types of structures of C code, for example a single statement, a “for” loop, a “if” statement, a function call and so on, those step types differ in varying degrees of skip of some of them. With these step types, you can go to almost any place in the code quickly and accurately. • Toggle breakpoint: to set a breakpoint in front of a line. • Remove all program breakpoints: as its name says. • Quickwatch: to turn to quickwatch window. And there is also a new window called “watch”, in which user can add a certain variable to the name list and see the value, type and location of it. Programming Using AVR Studio 4 43 GROUP 6 DISPLACEMENT MEASURING USING XYZ ACCELEROMETER SENSOR Fig. 5.15 On the right side of AVR Studio, there is another window “I/O View”, which provides powerful function to look at the data in the standard input and output pins bits and many AVR data registers data bits, and function to change the data bits. User can find an interesting data register by its precompiled name and see the value in its 8 or more bits. Blank square means this bit is 0 in binary while filled one stands for 1. Clicking on the square can turn the bit between 1 and 0. Actually, these registers in the “I/O View” window represent corresponding real registers and memory positions on the micro controller. Now you are only dealing with their “copies” in AVR Studio. It is right the simulated way talked above, to access these register. Fig. 5.16 Programming Using AVR Studio 4 44 GROUP 6 DISPLACEMENT MEASURING USING XYZ ACCELEROMETER SENSOR 5.5.2 Simplest and most powerful debug way Among all the functions above, there is one simplest but also a most powerful usage of debugging as following: Step1: Decide a certain variable we want to track. Option1: If the variable is a standard register. Step2: Set a breakpoint on the line in which the variable is used. Step3: Start debugging. Step4: Using an appropriate step type go to the breakpoint. Step5: Look at the “I/O View” window and check the data bits of the variable. Option2: if the variable is user defined. Step2: Set a breakpoint on the line in which the variable is initialized and used. Step3: Start debugging. Step4: Add the variable to the “watch” window. Step5: Using an appropriate step type go to the breakpoint. Step6: Look at the “watch” window and see the value. So now, with powerful debugging and simulating functions provided by AVR Studio, programmer can see what happens in the memory by “watch” window and “I/O view window”, to check and test the code, during the running of the code. Programming Using AVR Studio 4 45 GROUP 6 DISPLACEMENT MEASURING USING XYZ ACCELEROMETER SENSOR 5.6 Programming and Settings 5.6.1 Overview To put the C codes into the microcontroller and make all the related device work with these codes, a programming procedure is needed. Programming the device needs first to connect the target device, and then choose appropriate options for a certain AVR project. 5.6.2 Connect the target device To connect the target device, connect the RS232 [For RS232 description, see Chapter 4, Hardware layer.]. And turn on the power of the board. Then click “Tools” button on the menu bar, select “Program AVR”, then select “Connect…”. Fig. 5.17 Programming Using AVR Studio 4 46 GROUP 6 DISPLACEMENT MEASURING USING XYZ ACCELEROMETER SENSOR In the following window, choose STK500 as platform and the correct port on PC. COM number for PC-board connection can be found in PC’s “Control PanelDevice ManagerPorts and COMs”. “Auto” can be a better choice without checking the COM number. At last click “Connect…” button. Fig. 5.18 After few seconds, if the window goes back to this setting window again, connection fails. Check the hardware connection and COM number again to retry. If connection succeeds, a setting window for programming settings appears. 5.6.3 Programming setting 5.6.3.1 Main tab Successful connection to the STK500 board will lead to the programming settings window. To program the micro controller on the board, first make sure the board is connected in ISP mode [For ISP description, see Chapter 13.1.3, Part three – PC Programming Using AVR Studio 4 47 GROUP 6 DISPLACEMENT MEASURING USING XYZ ACCELEROMETER SENSOR connection.]. Then in “Main” tab, select ATmega16 as the device and ISP mode as the programming mode. Fig. 5.19 Then click “Settings…” button to set the frequency for ISP clock. This frequency must be less than 1/4 of the micro controller’s CPU clock frequency. There are several possibilities of the micro controller’s CPU clock frequency. [To see different choices of these clock frequencies, please refer to STK500 user guide, section 3, 3.8.4 Clock settings, XTAL1 and OSCSEL, and for corresponding fuses settings, please refer to 4.5.2.2. All these documents can be found on the CD attached to this document] Design and Implementation of Embedded Software 54 GROUP 6 DISPLACEMENT MEASURING USING XYZ ACCELEROMETER SENSOR Accelerometer sensor sends data standing for the accelerations in voltages. [For hardware description of accelerometer sensor, please refer to Chapter 4, Hardware layer] However, high voltage on a certain pin means binary 1 to the software and low voltage means 0. (Or it can be reverse in many cases) So software cannot receive concrete voltage signal on the pins. Thus, data from sensor cannot be read directly by the code, but need to be sent to a certain part of the microcontroller and be converted to a softwarereadable data form. This conversion is called ADC (it will be discussed in next topic, so just remember this name here). Though data come from the sensor’s output pins to the microcontroller’s input pins, the meaningful receiving and recognizing the data from sensor begins after ADC and is actually receiving the ADC result. 6.3.3 Analog-to-digital Conversion (ADC) 6.3.3.1 Introduction of ADC ADC stands for analog-to-digital converter or analog-to-digital conversion. When standing for the former, it means “a device that converts a continuous quantity to a discrete digital number”[14] and typically means “an electronic device that converts an input analog voltage (or current) to a digital number proportional to the magnitude of the voltage or current”[14]. And the latter is the function and the job of the former. DAC can be a reverse of ADC. Hereinafter, ADC will be used instead of its full name in most cases. The exact meaning can be inferred from the context. When it comes to a procedure or a function, it Design and Implementation of Embedded Software 55 GROUP 6 DISPLACEMENT MEASURING USING XYZ ACCELEROMETER SENSOR refers to a conversion while it means converter in case of a component or the subject of a conversion. 6.3.3.2 Reason to do ADC ADC has two main functions: • Making data readable for certain receiver. • Reducing the influence of the noise. First function is referred to in 5.2.1. ADC can convert voltage signals to digital numbers which are meaningful to software. Second function is the main reason so many electronic devices employ ADC. Suppose there is a certain data source sending data in voltage form in a large frequency that data signals can be regarded as continuous in every second. This is a graph of its signal stream. Horizontal axis value represents the time point when a certain signal is sent, and vertical axis shows the value of the signal. This is also a graph of original analog signal, which means the serials of analog values are what the source really wants to send. And the best outcome of these signals is that they are received in the same value when they are sent. Fig. 6.1 0 2 3 2 0 -2 -3 -2 0 2 3 2 0 -2 -3 -2 0 -4 -2 0 2 4 012345678 Value Time (s) Original Analog Signal Design and Implementation of Embedded Software 56 GROUP 6 DISPLACEMENT MEASURING USING XYZ ACCELEROMETER SENSOR Unfortunately, there are always kinds of errors and noises in the data transfer wires. In other words, these original analog signals will be influenced by noises when they leave the source and begin their adventures in wires. Suppose that, normally the noises change the signal by ±0.5. So value 3, for example, is possible to appear as any numbers between 2.5 to 3.5 in the receiving terminal. What is worse is that sometimes (not always), some kind of unexpected things happens in the transfer wires changing the value in a larger range. For example, the 0 can become 1.2 or even bigger. Fig. 6.2 So this graph could be one of the possible received analog signal streams. Compared new one (dark blue line) with the original one (light blue line), most values vary in the range of 0.5, and some value changed a lot. No matter the big change or small change, it is different from what the data source wants to send. So, some kind of information is wrong after data transfer in analog way. A digital transfer way can solve this problem in most times. Again, there is a same original analog signal stream from data source. Now do ADC. Distribute continuous signals into some separate number regions. The rule is that every integer number “i” and numbers in the range i±0.5 will come into the number -0,2 1,6 2,7 1,7 0,5 -1,2 -2 -1 1,2 2,2 2,6 2,4 0,5 -1,6 -2,6 -1,6 0,5 -4 -2 0 2 4 012345678 Value Time (s) Received Analog Signal Design and Implementation of Embedded Software 57 GROUP 6 DISPLACEMENT MEASURING USING XYZ ACCELEROMETER SENSOR region 50*i. For example, numbers from 1.5 to 2.5 become 50. To avoid duplicates in different number region, the strict requirement is for a certain number “k”, try to find the integer “i” satisfying the formula: i-0.5 < k <= i+0.5 then put “k” into the number region “50*i”. Fig. 6.3 Follow the rules and get the result of ADC is like the graph below. Continuous analog values are separated into discrete digital values. These are called original digital signals. Fig. 6.4 When transfer begins, these signals are also going to suffer from noises. For different reasons of noises, the change of a certain value can either keep in constant or 0 100 150 100 0 -100 -150 -100 0 100 150 100 0 -100 -150 -100 0 -200 -150 -100 -50 0 50 100 150 200 0 1 2 3 4 5 6 7 8 Value Time (s) Original Digitla Signal Design and Implementation of Embedded Software 58 GROUP 6 DISPLACEMENT MEASURING USING XYZ ACCELEROMETER SENSOR be in proportion to its value. A worse situation (the latter situation) will be used to prove the advantage of ADC. Fig. 6.5 This is a possible received digital signal graph. Compared the received values (dark blue rectangles) with the original ones (light blue rectangles), most values vary in the range of ±25 (no longer ±0.5 but in proportion to the value), and some values even changed more (for example 58 from 0). In fact, most of these noises only influence digital signal, and the negative effects can be remove after the last part of digital transfer way, the DAC. The rule of DAC is like a reverse of ADC rule. For a certain received digital signal “m”, try to find a multiple of 50 “n” satisfying the formula: n-25 < m <= n+25 then “m” will be converted to the number “n/50”. 24 120 126 124 58 -124 -173 -119 -20 80 126 109 10 -120-129-105 -20 -200 -150 -100 -50 0 50 100 150 200 012345678 Value Time (s) Received Digitla Signal Design and Implementation of Embedded Software 59 GROUP 6 DISPLACEMENT MEASURING USING XYZ ACCELEROMETER SENSOR Fig. 6.6 For example 100-25 < 124 <= 100+25, then 124 is converted to 2. Thus, the received digital signal will be converted to analog signal. Now the result analog signals (dark blue line) are more similar to the original signals (light blue line). In fact, DAC can remove all effects on digital values change in the DAC-rule-range, which in this case is 50. And changes larger than that will still exist. Fig. 6.7 Though the digital way cannot 100% avoid the influence by noises, it can guarantee the data quality in a large scale. And there are several ways to promote the quality: Take more samples in signal stream when do ADC. Current sample rate is 0.5 second. If it is more frequent, the final result will be more reliable. 0 2 3 2 1 -2 -4 -2 0 2 3 2 0 -2 -3 -2 0 -4 -2 0 2 4 012345678 Value Time (s) Received Analog Signal Design and Implementation of Embedded Software 60 GROUP 6 DISPLACEMENT MEASURING USING XYZ ACCELEROMETER SENSOR Define more digital levels when do ADC. Current level is multiples of 50. A higher degree of accuracy can be reached if digital level is multiples of 10. Take less samples of the final result. Current sample rate is 0.5 second, and the precision rate is 15/17, about 88%. If reduce sample rate to 1 second, and begins from 0.5, the precision rate can be 100%. So this is the reason to do ADC is a good data quality is required. Also be aware of that, conversion itself still needs transfer analog data, but if ADC is inside the data source, influence of the wires in internal circuit can be very low. If it is impossible to do ADC in the data source then it is better to do it as earlier as possible, because the longer distance the analog data travelled, the more noises and errors they suffered, and the low reliability they have. 6.3.3.3 ADC method and settings The accelerometer sensor picked has no inside ADC, while the microcontroller has an on-chip ADC. In this case, the only choice is to do ADC in microcontroller. The inbuilt ADC is multiplexed with PORTA that means the ADC channels for signal input are shared with PORTA. [For ports on STK500, please refer to Chapter 13.1, Quick start tutorial] And to use the inbuilt ADC is to set the register of ADC. ADC has 4 registers: • ADMUX Register. ADC Multiplexer Selection Register: For selecting the reference voltage and the input channel Design and Implementation of Embedded Software 61 GROUP 6 DISPLACEMENT MEASURING USING XYZ ACCELEROMETER SENSOR Table 6.1 REFS1 REFS0 selects the reference voltage as below: Table 6.2 AVCC is the voltage on the board, is 5v. And it is selected as the voltage reference. • ADCSRA Register. ADC Control and Status Register A: It has the status of ADC and is used for controlling it. Table 6.3 ADEN should be 1 when ADC is enabled. ADSC should be 1 when a conversion is needed. ADIF is the interrupt bit. It is set to 1 by the hardware when conversion is complete. This is the loop for waiting till conversion is complete. ADPS2-ADPS0 select the “prescaler” for ADC. The ADC frequency must be between 50 KHz to 200 KHz according to the hardware. And certain frequency can be Bit No. 7 6 5 4 3 2 1 0 Bit Name REFS1 REFS0 ADLAR MUX4 MUX3 MUX2 MUX1 MUX0 Initial Value 0 0 0 0 0 0 0 0 REFS1 REFS0 Voltage Reference 0 0 ARef intern al Vref Turned off 0 1 AVCC 1 0 -- 1 1 Internal 2.56 Voltage Reference Bit No. 7 6 5 4 3 2 1 0 Bit Name ADEN ADSC ADATE ADIF ADIE ADPS2 ADPS1 ADPS0 Initial Value 0 0 0 0 0 0 0 0 Design and Implementation of Embedded Software 62 GROUP 6 DISPLACEMENT MEASURING USING XYZ ACCELEROMETER SENSOR reached when divide the micro controller’s clock frequency by the “prescaler factor”. [For MCU clock frequency hardware connections, please refer to SDK500 user guide, and for software settings, please refer to Chapter 5.6.3, Programming setting] Table 6.4 From 16 MHz clock, the “prescaler factor” should be 128. Thus the ADC frequency 16000000/128=125000 Hz = 125 kHz is in the range between 50 kHz to 200 kHz. So ADPS2, ADPS1 and ADPS0 all need to be set to 1. • ADC (ADCL and ADCH) Register. The ADC Data Register (Low bits and High bits): To put the final result of conversion. Thus, ADC procedure in this project is: Step1: Initialize ADC (enable ADC, set reference voltage, set prescaler). Step2: Start ADC (set ADSC). Step3: Wait (use ADIF to judge). Step4: Read ADC result (read ADC (ADCL, ADCH)). ADPS2 APDS 1 ADP S0 P rescaler Factor 0 0 0 2 0 0 1 2 0 1 0 4 0 1 1 8 1 0 0 16 1 0 1 32 1 1 0 64 1 1 1 128 Design and Implementation of Embedded Software 63 GROUP 6 DISPLACEMENT MEASURING USING XYZ ACCELEROMETER SENSOR 6.3.3.4 ADC rule and result format ADC rule in this software is convert analog voltage 0v-5v to digital numbers 0- 1023, using linear project formula: Voltage Value 5=ADC result 1023 Sensors output voltage normally will be 0v-3.3v or sometimes 0v-3.6v. The ADC result in this case will be numbers between 0 and 737. [for accelerometer sensor’s output data information, please refer to ADXL335 datasheet[16] ] And this number can be read from ADC (ADCL and ADCH) as a 16bits unsigned integer. 6.3.4 Get Acceleration from Digital Numbers (ADC Results) 6.3.4.1 Overview and problems to solve ADC results are numbers standing for voltages, and those voltages represent the acceleration of the sensor on a certain axis. For accelerometer sensor’s working theory and output result according to acceleration, please refer to ADXL335 data sheet. [15] So there is a relationship between ADC result and acceleration. But it is not that easy to get the acceleration from ADC result directly though lots of technical details are provided. Following are the problems occur in this module. Problem 1: Noise on the wire and data jitter. As explained above, the sensor’s biggest drawback is non inbuilt ADC. Analog voltage signals have to go through the wires between sensor and micro controller, which Design and Implementation of Embedded Software 70 GROUP 6 DISPLACEMENT MEASURING USING XYZ ACCELEROMETER SENSOR Fig. 6.10 Regardless of the real start point of the repetitive sequence, a cycle of 1 second can be found in the time line. 6.3.5 Calculate Displacement from Acceleration and Time 6.3.5.1 Overview and formula introduction Physical equation of displacement, velocity, acceleration and time: s = 1 2at ଶ + vt Here, “t” is time period, “s” is displacement in time “t”, “a” is acceleration in time “t” and “v” is initial velocity in time “t”. Physical equation of velocity, acceleration and time: v = at + v ଴ Here, “t” is time period, “a” is acceleration in time “t”, “v 0 ” is initial velocity in time “t” and “v” is final velocity in time “t”. Theoretically, infinitely small time periods can be integrated to a continuous time period, so knowing the acceleration for each is knowing the acceleration all the time Design and Implementation of Embedded Software 71 GROUP 6 DISPLACEMENT MEASURING USING XYZ ACCELEROMETER SENSOR while in practice, CPU or software works in a high frequency to implement the continuity which is a simulative and mechanical way of integration, so there is no need to use abstract and complicated integral formula but only to calculate the displacement in each period and accumulate them. 6.3.5.2 Mathematical algorithm Algorithm expressed in mathematical language: Every same period of time is marked as “dt”. For the “n” th period of time, there is an acceleration “a n ”, corresponding initial velocity “v n ” and displacement “s n ”. In every “dt”, s ୬ =1 2a ୬ dt ଶ + v ୬ dt And v ୬ = a ୬ିଵ dt + v ୬ିଵ Similarly v ୬ିଵ = a ୬ିଶ dt + v ୬ିଶ … Till v ଶ = a ଵ dt + v ଵ v ଵ = a ଴ dt + v ଴ Iterate all the n-1 equations and get: v ୬ =a ୧ dt ୬ିଵ ୧ୀ଴ + v ଴ Design and Implementation of Embedded Software 72 GROUP 6 DISPLACEMENT MEASURING USING XYZ ACCELEROMETER SENSOR In fact “v 0 ” can never be known according to the device. But described in 5.2.3.4, all the algorithms are under the condition that the sensor is started in a static status, meaning that the “v 0 ” is 0. Thus, v ୬ =a ୧ dt ୬ିଵ ୧ୀ଴ , n > 0 0, n = 0 And s ୬ =      1 2a ୬ dt ଶ +a ୧ dt ଶ ୬ିଵ ୧ୀ଴ , n > 0 1 2a ୬ dt ଶ , n = 0 To make it more clear s ୬ =      a ୬ 2+a ୧ ୬ିଵ ୧ୀ଴ dt ଶ , n > 0 a ୬ 2dt ଶ , n = 0 And the total displacement is s ୧ ୬ ୧ୀ଴ 6.3.5.3 Program algorithm The same algorithm expressed in program language: dt: 1 second time cycle also the calculation loop cycle. Design and Implementation of Embedded Software 73 GROUP 6 DISPLACEMENT MEASURING USING XYZ ACCELEROMETER SENSOR ds: displacement in each calculation loop. a_sum: sum of accelerations of all previous calculation loops. a_cur: accelerations of current calculation loop. s_sum: total displacement (final result). Initialize all variables as follow: dt=1; ds=0; a_sum=0; a_cur=0; s_sum=0; Then in calculation loops: Previous data-coming loops have already sent the current acceleration, so a_cur is known before the while loop. While (calculation enabled) { ds= (a_cur/2+a_sum) * dt 2 ; s_sum=s_sum+ds; a_sum=a_sum+a_cur; }; Then, at any time s_sum will be the final displacement on a certain axis. To get the resultant displacement of sensor, make quadratic sum of displacements on all axis. Design and Implementation of Embedded Software 74 GROUP 6 DISPLACEMENT MEASURING USING XYZ ACCELEROMETER SENSOR 6.3.6 Use LCD as a Display Component 6.3.6.1 Reason to choose LCD To display the displacement data inside the memory, there are several choices. Using 8 LEDs to represent the value of displacement can be easy and sensitive but unspecific. Using PC screen can be both sensitive and detailed but is too advanced and is not so convenient that connection to PC is needed every time the device is used. Though PC display is developed in this project, it is provided as an extra and advanced component. [For PC-board connection please refer to Chapter 13.1.3, Part three – PC connection. For PC display software please refer to Chapter 7, Design and Implementation of “Power Viewer”, the PC Display Software] Finally, LCD is chosen because it is not only easy and detailed, but also portable. [For information on LCD please refer to Chapter 4, Hardware Layer] 6.3.6.2 LCD using method and output result LCD is not a standard on-board component provided AVR, so using LCD needs to make physical connection between board and LCD and adding LCD library to AVR project. [For LCD connections, please refer to Chapter 13.1.2, Part two – assembly] There is a tutorial about using a similar LCD in AVR program, and the LCD library and sample codes are provided in this tutorial. Refer to [18] for learning the tutorial and refer to [17] for downloading the files directly. Design and Implementation of Embedded Sof GROUP 6 DISPLACEMENT MEASURING USING XYZ ACCELEROMETER SENSOR For how to add 5.3.2, a dd external library to the project After adding the LCD library to the AVR program, start to use it by including the head file of it. Send characters or numbers as display forms can be found LCD display codes is in LCD loops, which will be carry out every 1 second (current version) using the TIMER0 Chapter 6.3.9, Using the TIMER0 to Get Time] loop. Output result of LCD in this project (current version) is using first line showing the resultant displacement in displacement component of X, Y and Z axis (from left to right) in three a sign. Check the numbers by calculating the line and comparing it with display: (-74) 2 + 129 2 Design and Implementation of Embedded Sof tware DISPLACEMENT MEASURING USING XYZ ACCELEROMETER SENSOR For how to add an external library to the AVR program, please refer to dd external library to the project or refer to the tutorial. [18] adding the LCD library to the AVR program, start to use it by including the Send characters or numbers as parameter s to different LCD functions display forms can be found in these functions. LCD display codes is in LCD loops, which will be carry out every 1 second (current version) using the TIMER0 register [For i nformation on TIMER0 register, please refer to Chapter 6.3.9, Using the TIMER0 to Get Time] . So it is a followup function of calculation Output result of LCD in this project (current version) is using first line showing the resultant displacement in a fivedigit number, and using the second line displaying signed displacement component of X, Y and Z axis (from left to right) in three Fig. 6.11 Check the numbers by calculating the quadratic sum of numbers in the seco line and comparing it with square of the resultant displacement. + (-117) 2 = 35806, and it is about the square 75 external library to the AVR program, please refer to Chapter [18] adding the LCD library to the AVR program, start to use it by including the s to different LCD functions . Kinds of LCD display codes is in LCD loops, which will be carry out every 1 second (current nformation on TIMER0 register, please refer to up function of calculation Output result of LCD in this project (current version) is using first line showing the digit number, and using the second line displaying signed displacement component of X, Y and Z axis (from left to right) in three -digit numbers with of numbers in the seco nd of the resultant displacement. In the example of the of 189.22 Design and Implementation of Embedded Software 76 GROUP 6 DISPLACEMENT MEASURING USING XYZ ACCELEROMETER SENSOR 6.3.7 Communicate with PC Through Serial Port 6.3.7.1 Overview It is an advanced function to enable the board-PC communication. The communication is based on serial ports on the board and PC under RS232 standard. In telecommunications, RS-232 (Recommended Standard 232) is a standard for serial binary single-ended data and control signals connecting between a DTE (Data Terminal Equipment) and a DCE (Data Circuit-terminating Equipment). It is commonly used in computer serial ports. The standard defines the electrical characteristics and timing of signals, the meaning of signals, and the physical size and pinout of connectors. [19] Since most of modern laptops and PCs do not have a serial port. A USB-serial port converter is needed. [For information on USB-serial port converter, please refer to Chpater 4, Hardware layer] This converter still use RS232 standard. But there is no need to go through all the RS232 rules, because AVR Studio supports powerful advanced RS232 communication using its USART. USART stands for “universal synchronous asynchronous receiver transmitter”. USART can be used to establish the connection. 6.3.7.2 UASRT register usage and setting Knowledge and technique on this field is provided by “extremeelectronics.co.in”. For more information on the USART, please refer to the tutorial [20]. For a sample Design and Implementation of Embedded Software 77 GROUP 6 DISPLACEMENT MEASURING USING XYZ ACCELEROMETER SENSOR program, please refer to the tutorial. [21] For RS232 basics, please refer to the tutorial.[22] Similar to ADC, AVR USART is connected to the CPU by several data registers. To use USART is to set the following six registers. • UDR Register USART Data Register: Read it to get the data stored in receive buffer of it and write data to send data to the transmitters buffer of it. • UCSRA Register USART Control and status Register A: It stores some status about the USART and can be used to configure the USART. Table 6.4 RXC is set to 1 when the USART has completed receiving a byte and data are available to be read from UDR TXC is set to 1 when the USART has completed transmitting a byte and data are available to be write to UDR • UCSRB Register USART Control and Status Register B: Similar to UCSRA. Bit No. 7 6 5 4 3 2 1 0 Bit Name RXC TXC UDRE FE DOR PE U2X -- Initial Value 0 0 1 0 0 0 0 -- Design and Implementation of Embedded Software 78 GROUP 6 DISPLACEMENT MEASURING USING XYZ ACCELEROMETER SENSOR Table 6.5 RXCIE stands for “receive complete interrupt enable” and is set to 1 if the associated interrupt is enabled. TXCIE stands for “transmit complete interrupt enable” and is set to 1 if the associated interrupt is enabled. RXEN is “receiver enable”. It should be 1 if the USART receiver is enabled. TXEN is “transmitter enable”. It should be 1 if the USART transmitter is enabled. In this program RXEN and TXEN should be 1 for both read and write data to PC. And in the software loops, an endless and unceasing data sending is needed, which means the micro controller needs always send acceleration data and other kind of data to PC. TXCIE should be 1 to enable the interrupt, so that if the transmitting of one byte is finished, the interrupt will inform the hardware as soon as possible in order to begin a transmitting of next byte. • UCSRC Register USART Control and Status Register C: Similar to UCSRA and UCSRB. Table 6.6 Bit No. 7 6 5 4 3 2 1 0 Bit Name RXCIE TXCIE UDRIE RXEN TXEN UCSZ2 RXB8 -- Initial Value 0 0 0 0 0 0 0 -- Bit No. 7 6 5 4 3 2 1 0 Bit Name URSEL UMSEL UPM1 UPM0 USBS UCSZ1 UCSZ0 -- Initial Value 0 0 0 0 0 0 0 -- Design and Implementation of Embedded Software 79 GROUP 6 DISPLACEMENT MEASURING USING XYZ ACCELEROMETER SENSOR URSEL is “USART register select”. Since the UCSRC and the UBRRH (see context below) register share a same address, URSEL is used to determine the aim register. If it is 1, the data is written to UCSRC, otherwise data is written to UBRRH. UMSEL is “USART mode select” which is used to select the communication mode, 1 for synchronous mode while 0 for asynchronous. Asynchronous is chosen as the mode, as it is more common. USBS is “USART stop bit select”, which selects the number of stop bits in the data transfer in RS232. 1 means 2 stop bits and 0 is 1 stop bit. The latter is chosen as it is more common. UCSZ is “USART character size”. There are 3 bits of UCSZ one is in the UCSRB and two are here. These 3 bits selects the number of bits to be transmitted in each frame. UCSZ2 UCSZ1 UCSZ0 Character Size (bits) 0 0 0 5 0 0 1 6 0 1 0 7 0 1 1 8 1 0 0 -- 1 0 1 -- 1 1 0 -- 1 1 1 9 Table 6.7 Because the character size in C is usually the multiple of 4 bits, and the most commonly used data type is “8 bits char” and “16 bits int”. So 8 bits of character size is selected. • UBRR Register Design and Implementation of Embedded Software 86 GROUP 6 DISPLACEMENT MEASURING USING XYZ ACCELEROMETER SENSOR 1024 is chosen as the specific “prescaler”. So 61 counts is one second in the software. • TCNT0 Register Timer Counter 0: It is counting at the frequency of F_CPU/1024 now. • TIMSK Register Timer Interrupt Mask Register: There are 3 timers in AVR. TIMER0 is only one of them. This register controls interrupts of all the 3 timers but last two bits are for TIMER0. Table 6.11 OCIE0 and TOIE0 can enable 2 kinds of interrupts in TIMER0. Only overflow interrupt is needed in the software. So, set TOIE0 to 1 to enable the overflow interrupt. Now, steps of using TIMER0 in the software are: Step1: Initialize TIMER0 (set TCCR0, TCNT0 and TIMSK to make “prescaler” be 1024, make counter start from 0 and enable overflow interrupt). Step2: Initialize global variable for counting time (variable to count 61 times). Step3: Overwrite a specific ISR while enable global interrupts by “sei()”. Bit No. 7 6 5 4 3 2 1 0 Bit Name -- -- -- -- -- -- OCIE0 TOIE0 I nitial Value 0 0 0 0 0 0 0 0 Design and Implementation of Embedded Software 87 GROUP 6 DISPLACEMENT MEASURING USING XYZ ACCELEROMETER SENSOR 6.3.10 Precision Statement and Error Reducing 6.3.10.1 Algorithm precision statement Precision of the whole displacement measuring system depends on two parts: hardware and software. Here is the software precision statement. “Precision” here means the fidelities of processed data in every software links compared with the original data. The original data is sensor’s output voltage values. • ADC Voltage signals are always suffered from noises on the wires, according to some previous experiments, ADC results jitter in a range of ±20. According to the sensitivity of the sensor, a 20 value means 20/67.25=0.2974g, and is an acceleration of about 2.91 m/s 2 . • ADC result collection and calibration Under the assumption of the homogeneous jitter, using collection and calibration algorithm, most positive and negative errors are cancelled out. The left offset of noise is about 0-5 in value, according to some experiments. 0-5 means 0-0.73 m/s 2 in acceleration. (This error is totally because of the sensor and wires, see ADXL335 data sheet for its precision statement [25] • Calculation Possible decimal parameters used in displacement calculation are in “float” data type. C language style “float” has a precision of 6 digits after decimal point. And the precision will not lose after addition, multiplication or calculation of square root. So precision in calculation is all the time at 0.000001 which will be covered by error in ADC result collection and calibration. Design and Implementation of Embedded Software 88 GROUP 6 DISPLACEMENT MEASURING USING XYZ ACCELEROMETER SENSOR • Gravity constant Gravity constant is 9.815 m/s 2 in the software. It is precise at 0.01. • LCD LCD will show the integer part of a value, while the real information is not lost. • PC-board connection The micro controller send ADC sample result in integer, with no precision lost. It sends accelerations accurate to 0.1 and displacement accurate to 0.01. Precision lost in data sending will never influence the calculation in the micro controller, but will cause an accuracy problem in PC. To sum up, displacement measuring system’s precision in software layer is 0.01. And the error of the result mostly comes from hardware layer. 6.3.10.2 Error reducing There are several error reducing algorithms in the software mainly to remove the error from hardware (sensor and wires). • ADC result collection and calibration algorithm Fuzzy compare While comparing two average samples of ADC result [see flow chart on Chapter 6.3.4.6, algorithms gathering and optimize], a value called “noise offset” is used to make a fuzzy compare. Because it is a 0-5 float in the value , a fuzzy compare is needed to recognize two same values within a difference of 5. For example two static status of the sensor may give 2 average samples in 400 time of sampling. Usually they are not the same in value according hardware error. If regard one of them as the real value of static and make a strict comparing, the other one will be regarded as a value of movement. In fact it Design and Implementation of Embedded Software 89 GROUP 6 DISPLACEMENT MEASURING USING XYZ ACCELEROMETER SENSOR is incorrect. The noise offset is such a factor to avoid those situations in most cases. However, it in turn, is also a source of error. There are also possibilities that two different values of different status, values of which differ in the range of the offset value, and they are treated the one. So there is certain case that the sensor is stopped but the data is keeping increasing. Fuzzy compare reduces error to a certain extent but cannot avoid all influences by error. • F_CPU choosing As it was discussed, for baud rate 19200bps, 16MHz F_CPU is a good choice to reduce transmitting errors. • Time counter and ISR time error As is discussed in 6.3.9.2, only assignments operations and addition operations are in ISR to reduce its CPU- intervenes time in order to reduce errors. 90 GROUP 6 DISPLACEMENT MEASURING USING XYZ ACCELEROMETER SENSOR Chapter 7 Design and Implementation of the PC Display Software Design and Implementation of the PC Display Software 91 GROUP 6 DISPLACEMENT MEASURING USING XYZ ACCELEROMETER SENSOR 7.1 PC Display Software Overview In order to provide a better expression of data and keep track of data in PC disk, “Power Viewer”, the PC display software is developed as an advanced component of the project. PC display software needs communication with the micro controller and exchange necessary data for controlling and display. This communication is established via serial port using RS232 standard, and is supported on the board-side with USART [For PC-board communication in embedded software, please refer to 6.3.7]. [For hardware connection support, please refer to Chapter 4, Hardware layer] Follow topics are based on current version of the software. Current version is the last edition before this report is handed. Future work may be done to promote the software or to remove some function modules. Changes and updates will be attached then. 7.2 Functions of PC Display Software and User Guide PC display software current version singly provides function of viewing data, though it is designed to visualize data in several ways and to keep a log file for data. But due to time limit, these higher functions are left for future. Here is a brief user guide: Conditions. All the data files and included source files (materials, pictures and external library of “Irrlicht Engine”) are set for the software’s debug version by relative path. No extra things are needed to open the execute file of debug version. Design and Implementation of the PC Display Software 92 GROUP 6 DISPLACEMENT MEASURING USING XYZ ACCELEROMETER SENSOR Copy the project file to PC’s disk and open “...\DM_PCDisplay\Debug\ DM_PCDisplay.exe”. Fig. 7.1 There occurs the welcome window, which shows the software’s name and title of the project. At the same time, the software is waiting for serial port connection to the micro controller. Now, check the hardware connections are in communication mode [For PC- board communication hardware connection, please refer to Chapter 13.1, Quick start]. And turn on the power of STK500 board. Fig. 7.2 Design and Implementation of the PC Display Software 93 GROUP 6 DISPLACEMENT MEASURING USING XYZ ACCELEROMETER SENSOR The center of the bottom is communication port number option. A correct “COM” number should be set by click the number button. Usually, it is “COM1”, but for sure, please go and check in “Control Panel Device ManagerPorts and COMs”. If the software failed to enter the specific port, it will stay in the page. Otherwise, a new window will occur. Fig. 7.3 Although the specific com is detected and connected, it may not be the com for the micro controller (maybe it is occupied by other device connected to this PC). For this case, the window above will remain blank (no any numbers in the table), and the software should be reopened. If the com is connected by the micro controller, then lots of numbers will soon appear. This is the main window of the software. And the default view is the “numeric data” view. It is an instantaneous data table of displacement measuring system, which Design and Implementation of the PC Display Software 94 GROUP 6 DISPLACEMENT MEASURING USING XYZ ACCELEROMETER SENSOR shows digital numbers, accelerations and displacements data from the micro controller in numeric way without any advanced processing. Fig. 7.4 Main menu of function selection is on the bottom. Several views are planned other than numeric data, like charts and real view. But current version only implements numeric view function. The new edition of user guide will attached if any updates and changed of the software is done. 7.3 Implementation of Current Version 7.3.1 Overview This software is developed in C++ language in Visual Studio 2008 and has occupied several external libraries in Irrlicht Engine. For information on these two tools, please refer to [26] It is developed in an object-oriented idea [27]. The whole framework is done, which means the structure of the software is done. Several basic C++ classes are designed and implemented, for example the powerful and customizable button class for user input processing and user-friendly interface and view classes in different levels for a structured software and so on. Adding a new module to the software will not be too difficult. Design and Implementation of the PC Display Software 95 GROUP 6 DISPLACEMENT MEASURING USING XYZ ACCELEROMETER SENSOR 7.3.2 Software Framework Design Since the software is developed in C++, there are many classes operating as independent units but forming a relationship net. To understand this net is to quickly know the idea of design this software. This object relationship chart is almost implemented now because the software framework is built, but some of the detail functions in it will be finished in the future. Fig. 7.5 Simply three circles can make a conclusion of the relationship between each class objects. Here are the explanations. First circle, on the upright, is the relation between user, interface and power viewer class. User will control the whole software by setting kinds global variables. For example, user needs to use a menu to select the current on-show view which though is a function point to a certain class of view, is not available until this view is called and initialized by the power viewer class. User may click a certain button for help and other Structure and Management of the Project 102 GROUP 6 DISPLACEMENT MEASURING USING XYZ ACCELEROMETER SENSOR Fig. 8.2 - Gantt chart Structure and Management of the Project 103 GROUP 6 DISPLACEMENT MEASURING USING XYZ ACCELEROMETER SENSOR 8.2.3 Responsibility Matrix (RM) It takes a lot of effort to keep a large project running smoothly. With a large number of variables, people, and deliverables, it’s hard to keep on top of everything that’s happening. That is why RM, presented here as a third tool might be useful. It is an important project communication tool because all members can see clearly who to contact for each activity [31] A responsibility matrix is a way to show graphically the responsibility of the particular member involved in the project in completing tasks.RM presented below shows not only the responsibility issue but also who is responsible for support in a particular activity. In this project the tasks were distributed equally so each member is responsible, more or less, for the same amount of work. Fig. 8.3 – Responsibility Matrix Structure and Management of the Project 104 GROUP 6 DISPLACEMENT MEASURING USING XYZ ACCELEROMETER SENSOR 8.3 Checking the Progress Process Each day of this semester the schedule has been followed. Project was proceeded according to presented above managing tools and sometimes unexpected situations. Issues and problems occurred and there were some delays in the project process. Due to those obstacles the schedule was reconstructed in order to adapt to new situation. 8.4 Dealing with Problems 8.4.1 Overview In the next paragraph, some of the main problems are presented. As a brief summary of the problem, an “ad-hoc” solution is given, for the future development of the device. According to confronted problems, project plans were reconstructed. Updated managing tools are presented below “troubles section”. 8.4.2 Troubles Section 8.4.2.1 Misunderstanding – STK502 At the very beginning the project, programming was done using many different components, which obviously took some time. As a great misunderstanding, work with STK502 as an extension board for STK500 can be presented. The processor (Atmega Tiny group) provided with the STK502 is a very uncomfortable to work with. What is more, to work with the display on the board, additional IDE is required. It is called IAR. It is not free software, only 30 days version is available for free. The way of compiling the program in one IDE (IAR), and programming the device using different IDE Structure and Management of the Project 105 GROUP 6 DISPLACEMENT MEASURING USING XYZ ACCELEROMETER SENSOR (AVR Studio) is very inefficient and uncomfortable. The problem is a great amount of time, which was wasted on adopting STK502 for project requirements. 8.4.2.2 Power First of all, main issue was the power. The board was supplied with the external 12V power supply. By inbuilt resistors and capacitors, as well as, internal circuits’ conversion from 12V to 5V, required by microcontroller, was done on the board without any interference. Problem occurred when working with accelerometer. It turned out, this low power devices requires power supply at level of approximately 3V, no more than 3.3 V. The problem was solved by using LD1117 voltage regulator. Another power issue occurred while attempting multiplexer to work with the division of the signals. It turned out this analog device needs 10V of power. Unfortunately, this problem was not solved, and it is left as a part of future work for next EPS teams. 8.4.2.3 Wires In order to measure displacement of walls, we need to have long wires. The length of wires my cause possible lost of data or errors in data transmission. In this section data is understood as an analog signal. That means this signal can be not strong enough to reach the destination without any change. Long wires are also a great opportunity for signal distortion by magnetic interference or any other mean that can influence on the signal. Solution might be to use the amplifier on the way of the signal to make it stronger, and implement some additional capacitors to clear the signal and remove power noise. This solution is also a part of future work, not implemented in the described prototype. Structure and Management of the Project 106 GROUP 6 DISPLACEMENT MEASURING USING XYZ ACCELEROMETER SENSOR 8.4.2.4 Multiplexer(MUX) At the beginning of the project the multiplexer was not included in the plans but in the middle of the semester adding one was suggested to expand the functions of the device. The challenge was accepted but the selection of the multiplexer took some time and it also took some time to get it from the dealer. When it finally arrived the MUX was soldered on a supplementary board and it was attached to the main board with the display and the rest of components. The time was the main problem. Final date of the project was on the horizon and there was not enough time to deal with other issues previously included in the schedule. The second reason was the power issue mentioned in one of the sections above. The solution might be to provide required power to the device and program it or to use digital, low power MUX suitable to work with digital signals. Digital MUX, as well as, digital accelerometers are already bought as a future extension of the project. 8.4.2.5 Crystal During the project development a decision to extend the requirements of PC connection was done. It turns out that in order to establish a connection between PC and evaluation board, using a RS232 serial protocol, adding an external crystal is required. Because of lack of any useful tutorial or documentation provided by the producer hours of useless research was done jus to find out how to make a microcontroller work with the external crystal. The goal was achieved by changing the jumpers on the board and reprogramming the fuses in the microcontroller. This step is considered as unexpected trouble issue because of lack of any support in the field of using external crystals. Structure and Management of the Project 107 GROUP 6 DISPLACEMENT MEASURING USING XYZ ACCELEROMETER SENSOR 8.4.2.6 Plan changes All this issues and problems changed the distribution of time in the project and finally a new GC to organize time was made. The next graphics reflects the status of the project at the second Project Review and the final status after dealing with the problems previously mentioned. Structure and Management of the Project 108 GROUP 6 DISPLACEMENT MEASURING USING XYZ ACCELEROMETER SENSOR 8.4 Status at Project Review 2 8.4.1 New Gantt Chart - Project Review 2 Fig. 8.4 – Gantt chart, Project Review 2 Structure and Management of the Project 109 GROUP 6 DISPLACEMENT MEASURING USING XYZ ACCELEROMETER SENSOR 8.4.2 Status of Work Breakdown Structure - Project Review 2 Fig. 8.5 – Work Breakdown Structure, Project Review 2 In the image above is possible to see the Work Breakdown Structure status at the Project Review 2, the green boxes mean that the work is done, yellow boxes the areas were the work was focused at that moment and blue boxes future tasks. Structure and Management of the Project 110 GROUP 6 DISPLACEMENT MEASURING USING XYZ ACCELEROMETER SENSOR 8.4.3 Status of Responsibility Matrix - Project Review 2 Fig. 8.6 – Responsibility matrix, Project Review 2 As it is shown in this responsibility matrix at that time most of the work was done (represented as “thick” in the picture), only the things related with the display were still on the TODO list. Jorge Liyue Lukasz Raquel Comments Status Accelerometers R S Search Microcontroller R S Search Connectors R S Search Software S R Search Compatibility S R Search Display S R S earch Sensor/MC R S Connection MC/Display R S Connection PC/Software R S Connection Receive Data R S Programming A/D S R Programming Display R S Programming 111 GROUP 6 DISPLACEMENT MEASURING USING XYZ ACCELEROMETER SENSOR Chapter 9 Future Work References 118 GROUP 6 DISPLACEMENT MEASURING USING XYZ ACCELEROMETER SENSOR [1]Hugh D. Young, Roger A. Freedman. University Physics Volume one, 9 th Edition.1996 [2] Alan Jeffrey. Essentials of engineering mathematics, 2 nd Edition. 2004 [3] Thomas L. Floyd. Electronics Fundamentals: Circuits, Devices and Applications. 7 th Edition.2007 [4] Jerry C. Whitaker. The electronics handbook. 2 nd Edition.2005 [5] Atmel Datasheet. [6] EVAL-ADXL335Z Datasheet. [7] ADXL335 Datasheet. [8] ATmega16 Datasheet. [9] LD1117 Data Sheet. [10] ADXL345 Datasheet. [11] Brian Barkley Graham. Using an Accelerometer Sensor to Measure Human Hand Motion. MIT ,2000. [12] http://www.arduino.cc [29/11/2010] [13] http://www.atmel.com/dyn/products/tools_card.asp?tool_id=2725&source=redirect [14] http://en.wikipedia.org/wiki/Analog-to-digital_converter [15] www.sparkfun.com/datasheets/Components/SMD/adxl335.pdf [16] www.sparkfun.com/datasheets/Components/SMD/adxl335.pdf [17] http://extremeelectronics.co.in/avr-tutorials/using-lcd-module-with-avrs/ [18] http://www.extremeelectronics.co.in/avrtutorials/download/lcd.zip [19] http://en.wikipedia.org/wiki/RS-232 References 119 GROUP 6 DISPLACEMENT MEASURING USING XYZ ACCELEROMETER SENSOR [20] http://extremeelectronics.co.in/avr-tutorials/using-the-usart-of-avr- microcontrollers/ [21] http://extremeelectronics.co.in/avr-tutorials/using-the-usart-of-avr- microcontrollers-reading-and-writing-data/ [22] http://extremeelectronics.co.in/avr-tutorials/rs232-communication-the- basics/ [23] http://en.wikipedia.org/wiki/Baud [24] http://extremeelectronics.co.in/avr-tutorials/avr-timers-an-introduction/ [25] http://www.sparkfun.com/datasheets/Components/SMD/adxl335.pdf [26]http://irrlicht.sourceforge.net/ [27] http://en.wikipedia.org/wiki/Object-oriented_programming 120 GROUP 6 DISPLACEMENT MEASURING USING XYZ ACCELEROMETER SENSOR Chapter 12 Glossary Glossary 121 GROUP 6 DISPLACEMENT MEASURING USING XYZ ACCELEROMETER SENSOR A ADC: Analog-to-digital Converter (Conversion). It is a device that converts a continuous quantity to a discrete digital number. The conversion is also called ADC. Analog data: An analog or analogue signal is any continuous signal for which the time varying feature (variable) of the signal is a representation of some other time varying quantity. B Build: In the field of software, build refers either to the process of converting source code files into standalone software artifact(s) that can be run on a computer, or the result of doing so. C CMOS: Complementary metal-oxide-semiconductor. It is a technology for constructing integrated circuits. Compiler: It is a computer program (or set of programs) that translates source code written in a computer language into another computer language (the target language). This procedure is called “compile”. CPU: Central Processing Unit. It is the part of an informatics system which realizes the instructions for a program. D Debug: Debugging is a methodical process of finding and reducing the number of bugs, or defects, in a computer program or a piece of electronic hardware, thus making it behave as expected. Digital data: In the report it mainly refers to discrete-time signals that have a discrete number of levels, for example a sampled and quantified analog signal. Glossary 122 GROUP 6 DISPLACEMENT MEASURING USING XYZ ACCELEROMETER SENSOR E EEPROM: Electrically Erasable Programmable Read-Only Memory. It is a type of non-volatile memory. Embedded: In computers, an Embedded system is a special-purpose system in which the computer is completely encapsulated by the device it controls. G GCC: The GNU Compiler Collection. It is a compiler system produced by the GNU Project supporting various programming languages. I I2C: Inter-Integrated Circuit. It is a serial bus used to connect low-speed peripherals to a motherboard. IDE: Integrated Development Environment. It is also known as integrated design environment or integrated debugging environment and is a software application that provides comprehensive facilities to computer programmers for software development. L LCD: Liquid Crystal Display. It is an electronic visual display which does not emit light directly. M MIPS: Microprocessor without Interlocked Pipeline Stages. It is the microcontroller’s family which use reduced RISC and it is developed by MIPS Computer Systems. P PWM: Pulse-Width Modulation. It is a technique for controlling power to inertial electrical devices. R RAM: Random-Access Memory. It is one of the forms to store computer data. Glossary 123 GROUP 6 DISPLACEMENT MEASURING USING XYZ ACCELEROMETER SENSOR RISC: Reduced Instruction Set Computing. It is a design strategy which uses simple instructions to reduce the runtime. ROHS: Restriction of Hazardous Substances Directive. RS-232: Recommended Standard 232. In telecommunications, RS-232 is a standard for serial binary single-ended data and control signals connecting between a DTE (Data Terminal Equipment) and a DCE (Data Circuit-terminating Equipment). It is commonly used in computer serial ports. S SCSI: Small Computer System Interface. It is a standard interface to transfer data between different devices using the computer’s bus. SPI: Serial Peripheral Interface Bus. It is a synchronous serial data link standard. U USART: Universal Synchronously/Asynchronous Receiver/Transmitter. It is a computer hardware that translates data between parallel and serial forms. V VCC: Common-collector voltage. 124 GROUP 6 DISPLACEMENT MEASURING USING XYZ ACCELEROMETER SENSOR Chapter 13 Appendix Appendix 125 GROUP 6 DISPLACEMENT MEASURING USING XYZ ACCELEROMETER SENSOR 13.1 Quick Start Tutorial 13.1.1 Tutorial Overview This tutorial is written in order to simplify quick start with the device. Presented document consist of 3 parts. In the first one, required components are presented. In the second section assembly process is presented step by step. In the last part of this tutorial steps to establish PC connection are being presented. In order to make to reader familiar with used term, below header names are presented in the picture. Fig. 1: Headers description. Appendix 126 GROUP 6 DISPLACEMENT MEASURING USING XYZ ACCELEROMETER SENSOR 13.1.2 Components STK500 evaluation board 1 A Tmega16 unit 1 Crystal 16MHz 1 LD1117AV33 voltage regulator 1 Potentiometers 10k 4 LCD 2x16 display 1 Jumpers 5 RS232 - USB converter 1 RS232 cable 1 Pin to pin wires 20 12 V power supply unit 1 Table 1 Below component are being presented. Fig. 2: Components. 13.1.2 Assembly Appendix GROUP 6 DISPLACEMENT MEASURING USING XYZ ACCELEROMETER SENSOR This section is written using step by step method. In order to construct the hardware layer correctly follow the steps in given order, not jumping between them. 1. Prepar e the STK500 evaluation board. In order to prepare the board make sure the power unit is disconnected. Then set up the jumpers as presented in the picture. This is default jumpers setting. 2. Plug in the ATmega16 in the Target AVR socket. 3. Connect ISP mode(programming mode), as it is shown on the picture above(Figure 4). DISPLACEMENT MEASURING USING XYZ ACCELEROMETER SENSOR This section is written using step by step method. In order to construct the hardware layer correctly follow the steps in given order, not jumping between them. e the STK500 evaluation board. In order to prepare the board make sure the power unit is disconnected. Then set up the jumpers as presented in the picture. This is default Fig 3 :Default jumpers Plug in the ATmega16 in the Target AVR Fig 4:STK500 - Connect ISP mode(programming mode), as it is shown on the picture 127 This section is written using step by step method. In order to construct the hardware layer correctly follow the steps in given order, not jumping between them. :Default jumpers . - ISP mode. Appendix 134 GROUP 6 DISPLACEMENT MEASURING USING XYZ ACCELEROMETER SENSOR 20th September – 26th September • Preparing presentation • Updating reports • Programming in C • Board and accelerometer matters 27th September- 3rd October • Binary and hexadecimal system operations • Atmega16 peripherals study • IO registers study • ADC registers study • LCD research • Electrical connections project • EAGLE software • Programming registers in C language 4th October-10th October • Project requirements • RS232 converter / WIN 7 • Constructing electronics 11th October-17th October • Interim report • Multiplexer research • Digital accelerometer ADXL345 research Appendix 135 GROUP 6 DISPLACEMENT MEASURING USING XYZ ACCELEROMETER SENSOR 25th October- 31st October • Work with the accelerometer (show the results via LEDs) • Display’s library research 1st November-7th November • Project review 2 presentation • Programming accelerometer • Programming display 8th November- 14th November • Programming display • Programming accelerometer 15th November- 21st November • Crystal research • Board-PC connection • Work with the multiplexer • 10v power supply research for the multiplexer 22nd November – 28th November • Final report • Algorithm • Choose the final crystal • PC software Appendix 136 GROUP 6 DISPLACEMENT MEASURING USING XYZ ACCELEROMETER SENSOR 29th November- 5th December • Final report • Algorithm • PC software