Fast and Effective Embedded Systems Design

Transcription

1 Fast and Effective Embedded Systems Design Applying the ARM mbed Rob Toulson Tim Wilmshurst AMSTERDAM BOSTON HEIDELBERG LONDON NEW YORK OXFORD чч*?? &Ш& PARIS SAN DIEGO SAN FRANCISCO SINGAPORE SYDNEY TOKYO % ELSEVIER Newnes is an imprint of Elsevier Newnes

2 Contents Introduction Acknowledgements xv xix PART I: Essentials of Embedded Systems, using the mbed Chapter 1: Embedded Systems, Microcontrollers and ARM Introducing Embedded Systems What is an Embedded System? An Example Embedded System Microprocessors and Microcontrollers Some Computer Essentials The Microcontroller Development Processes in Embedded Systems Programming Languages: What is so Special about C/C++? The Development Cycle The World of ARM A Little History Some Technical Detail: What does this RISC Word Mean? The Cortex Core 14 Chapter Review 15 Quiz 15 References 16 Chapter 2: Introducing the mbed Introducing the mbed The mbed Architecture The LPC1768 Microcontroller Getting Started with the mbed: A Tutorial 22 Step 1. Connecting the mbed to the PC 22 Step 2. Creating an mbed Account 23 v

3 vi Contents Step 3. Running a Program 23 Step 4. Compiling the Program 24 Step 5. Downloading the Program Binary Code 25 Step 6. Modifying the Program Code The Development Environment The mbed Compiler and API Using C/C++ 26 Chapter Review 26 Quiz 27 References 27 Chapter 3: Digital Input and Output Starting to Program Thinking about the First Program Understanding the mbed API Exploring the while Loop Voltages as Logic Values Digital Output on the mbed Using LEDs Using mbed External Pins Using Digital Inputs Connecting Switches to a Digital System The Digitalln API Using if to Respond to a Switch Input Interfacing Simple Opto Devices Opto Reflective and Transmissive Sensors Connecting an Opto-Sensor to the mbed Seven-Segment Displays Connecting a Seven-segment Display to the mbed Switching Larger DC Loads Applying Transistor Switching Switching a Motor with the mbed Switching Multiple Seven-Segment Displays Mini-Project: Letter Counter 53 Chapter Review 53 Quiz 53 References 55

4 Contents v/7 Chapter 4: Analog Output Introducing Data Conversion The Digital-to-Analog Converter Analog Outputs on the mbed Creating Constant Output Voltages Sawtooth Waveforms Testing the DAC Resolution Generating a Sine Wave Another Form of Analog Output: Pulse Width Modulation Pulse Width Modulation on the mbed Using the mbed PWM Sources Some Trial PWM Outputs Speed Control of a Small Motor Generating PWM in Software Servo Control Outputting to a Piezo Transducer 72 Chapter Review 74 Quiz 75 Reference 75 Chapter 5: Analog Input Analog-to-Digital Conversion The Analog-to-Digital Converter Range, Resolution and Quantization Sampling Frequency Analog Input with the mbed Combining Analog Input and Output Controlling LED Brightness by Variable Voltage Controlling LED Brightness by PWM Controlling PWM Frequency Processing Data from Analog Inputs Displaying Values on the Computer Screen Scaling ADC Outputs to Recognized Units Applying Averaging to Reduce Noise Some Simple Analog Sensors The Light-Dependent Resistor Integrated Circuit Temperature Sensor 89

5 viii Contents 5.5 Exploring Data Conversion Timing Estimating Conversion Time and Applying Nyquist Mini-Project: Two-Dimensional Light Tracking 92 Chapter Review 92 uiz Q 93 References 93 Chapter 6: Further Programming Techniques The Benefits of Considered Program Design and Structure Functions Program Design Using Flowcharts to Define Code Structure Pseudocode Working with Functions on the mbed Implementing a Seven-Segment Display Counter Function Reuse A More Complex Program Using Functions Using Multiple Files in C/C Overview of the C/C++ Program Compilation Process The C/C++ Preprocessor and Preprocessor Directives The mfndef Directive Using mbed Objects Globally Modular Program Example 109 Chapter Review 113 Quiz 113 Chapter 7: Starting with Serial Communication Introducing Synchronous Serial Communication Serial Peripheral Interface Introducing SPI SPI on the mbed Setting up an mbed SPI Master Creating a SPI Data Link Intelligent Instrumentation and a SPI Accelerometer Introducing the ADXL345 Accelerometer Developing a Simple ADXL345 Program Evaluating SPI 129

6 Contents ix 7.5 The Inter-Integrated Circuit Bus Introducing the I 2 C Bus I 2 C on the mbed Setting up an I 2 C Data Link Communicating with an I C Temperature Sensor Using the SRF08 Ultrasonic Range Finder Evaluating I 2 C Asynchronous Serial Data Communication Introducing Asynchronous Serial Data Applying Asynchronous Communication on the mbed Applying Synchronous Communication with the Host Computer Mini-Project: Multi-Node I 2 C Bus 144 Chapter Review 144 Quiz 145 References 145 Chapter 8: Liquid Crystal Displays Display Technologies Introducing Liquid Crystal Technology Liquid Crystal Character Displays Using the PC1602F LCD Introducing the PC1602F Display Connecting the PCI602F to the mbed Using Modular Coding to Interface the LCD Initializing the Display Sending Display Data to the LCD The Complete LCD.cpp Definition Utilizing the LCD Functions Adding Data to a Specified Location Using the mbed TextLCD Library Displaying Analog Input Data on the LCD More Advanced LCDs Color LCDs Controlling a SPI LCD Mobile Phone Display Mini-Project: Digital Spirit Level 166 Chapter Review 167 Quiz 167 References 167

7 x Contents Chapter 9: Interrupts, Timers and Tasks Time and Tasks in Embedded Systems Timers and Interrupts Tasks Event-Triggered and Time-Triggered Tasks Responding to Event-Triggered Events Polling Introducing Interrupts Simple Interrupts on the mbed Getting Deeper into Interrupts Interrupts on the LPC Testing Interrupt Latency Disabling Interrupts Interrupts from Analog Inputs Conclusion on Interrupts An Introduction to Timers The Digital Counter Using the Counter as a Timer Timers on the mbed Using the mbed Timer Using Multiple mbed Timers Testing the Timer Duration Using the mbed Timeout A Simple Timeout Application Further Use of Timeout Timeout used to Test Reaction Time Using the mbed Ticker Using Ticker for a Metronome Reflecting on Multi-Tasking in the Metronome Program The Real Time Clock Switch Debouncing Mini-Projects A Self-Contained Metronome Accelerometer Threshold Interrupt 198 Chapter Review 199 Quiz 199

8 Contents xi Chapter 10: Memory and Data Management A Memory Review Memory Function Types Essential Electronic Memory Types Using Data Files with the mbed Reviewing some Useful C/C++ Library Functions Defining the mbed Local File System Opening and Closing Files Writing and Reading File Data Example mbed Data File Access File Access String File Access Using Formatted Data Using External Memory with the mbed Introducing Pointers Mini-Project: Accelerometer Data Logging on Exceeding Threshold 214 Chapter Review 215 Quiz 216 References 216 PART II: Moving to Advanced and Specialist Applications Chapter 11: An Introduction to Digital Signal Processing What is a Digital Signal Processor? Digital Filtering Example An mbed DSP Example Input and Output of Digital Data Signal Reconstruction Adding a Digital Low-Pass Filter Adding a Push-Button Activation Digital High-Pass Filter Delay/Echo Effect Working with Wave Audio Files The Wave Information Header Reading the Wave File Header with the mbed Reading and Outputting Mono Wave Data Summary on DSP 239

9 xii Contents 11.7 Mini-Project: Stereo Wave Player Basic Stereo Wave Player Stereo Wave Player with PC Interface Portable Stereo Wave Player with Mobile Phone Display Interface 241 Chapter Review 241 Quiz 241 References 242 Chapter 12: Advanced Serial Communications Introducing Advanced Serial Communication Protocols Bluetooth Serial Communication Introducing Bluetooth Interfacing the RN-41 and RN-42 Bluetooth Modules Sending mbed Data over Bluetooth Receiving Bluetooth Data from a Host Terminal Application Communicating between Two mbeds on Bluetooth Introducing USB Using the mbed to Emulate a USB Mouse Sending USB MIDI Data from an mbed Introducing Ethernet Ethernet Overview Implementing Simple mbed Ethernet Communications Ethernet Communication between mbeds Local Network and Internet Communications with the mbed Using the mbed as an HTTP Client Using the mbed as an HTTP File Server Using Remote Procedure Calls to Modify mbed Outputs Controlling the mbed using a Remote JavaScript Interface 267 Chapter Review 270 Quiz 271 References 271 Chapter 13: An Introduction to Control Systems 273 I3.l Control Systems Closed and Open Loop Control Systems Closed Loop Cruise Control Example Proportional Control 276

10 Contents xiii Proportional Integral Derivative Control Closed Loop Digital Compass Example Using the HMC6352 Digital Compass Implementing a 360 Degree Rotation Servo Implementing a Closed Loop Control Algorithm Communicating Control Data over the Controller Area Network The Controller Area Network CAN on the mbed 289 Chapter Review 294 Quiz 294 References 295 Chapter 14: Letting Co of the mbed Libraries Introduction Control Register Concepts Digital Input/Output mbed Digital Input/Output Control Registers A Digital Output Application Adding a Second Digital Output Digital Inputs Getting Deeper into the Control Registers Pin Select and Pin Mode Registers Power Control and Clock Select Registers Using the DAC mbed DAC Control Registers A DAC Application Using the ADC mbed ADC Control Registers An ADC Application Changing ADC Conversion Speed A Conclusion on using the Control Registers 318 Chapter Review 319 Quiz 319 Reference 319 Chapter 15: Extension Projects Where do We Go from Here? Pololu Robot for mbed 321

11 xiv Contents 15.3 Advanced Audio Projects The Internet of Things Introducing the mbed LPCl 1U From mbed to Manufacture Closing Thoughts 329 References 329 Appendix A: Some Number Systems 337 Appendix B: Some С Essentials 339 Appendix C: mbed Technical Data 359 Appendix D: Parts List 365 Appendix E: The Tera Term Terminal Emulator 369 Index 373