Atmel's AVR microcontrollers are the chips that power Arduino, and are the go-to chip for many hobbyist and hardware hacking projects. In this book you'll set aside the layers of abstraction provided by the Arduino environment and learn how to program AVR microcontrollers directly. In doing so, you'll get closer to the chip and you'll be able to squeeze more power and features out of it.

Each chapter of this book is centered around projects that incorporate that particular microcontroller topic. Each project includes schematics, code, and illustrations of a working project.

• Program a range of AVR chips
• Extend and re-use other people's code and circuits
• Interface with USB, I2C, and SPI peripheral devices
• Learn to access the full range of power and speed of the microcontroller
• Build projects including Cylon Eyes, a Square-Wave Organ, an AM Radio, a Passive Light-Sensor Alarm, Temperature Logger, and more
• Understand what's happening behind the scenes even when using the Arduino IDE

Table of Contents

Part I. The Basics

1. Introduction
    What Is a Microcontroller? The Big Picture
        A Computer on a Chip…
        …But a Very Small Computer
        What Can Microcontrollers Do?
    Hardware: The Big Picture
        The Core: Processor, Memory, and I/O
        Peripherals: Making Your Life Easier

2. Programming AVRs
    Programming the AVR
        Toolchain
    The Software Toolchain
        Linux Setup
        Windows Setup
        Mac Setup
        Arduino Setup
        Make and Makefiles
    AVR and the Arduino
        Arduino Pros
        Arduino Cons
        The Arduino: Hardware or Software? Both!
        The Arduino Is an AVR
        The Arduino Is an AVR Programmer
    Other Hardware Programmers
        Flash Programmers I Have Known and Loved
    Getting Started: Blinking LEDs
        Hookup
        ISP Headers
        AVRDUDE
        Configuring Your Makefile
        Flash
        Troubleshooting

3. Digital Output
    blinkLED Redux
        The Structure of AVR C Code
        Hardware Registers
        blinkLED Summary
   POV Toy
        Building the Circuit
        Pretty Patterns: The POV Toy Code
        Experiment!

4. Bit Twiddling
    Working Through the Code: Cylon Eyes
    Bit Twiddling and Cylon Eyes
        Bit Shifting
    Advanced Bit Twiddling: Above and Beyond Cylon Eyes
        Setting Bits with OR
        Toggling Bits with XOR
        Clearing a Bit with AND and NOT
    Showing Off
    Summary

5. Serial I/O
    Serial Communication
    Implementing Serial Communication on the AVR: Loopback Project
        Setup: Configuring the AVR
        Setup: Your Computer
        Setup: USB-Serial Adapter
        Putting It All Together: Test Out Your Loopback
        Troubleshooting Serial Connections
    Configuring USART: The Nitty-Gritty Details
    AVR Square-Wave Organ
        Making Music with Your Micro
        The Organ Library
        The Code
        Extra Goodies
    Summary

6. Digital Input
    Pushbuttons, Switches, Etc.
        Configuring Input: DDRs, PORTs, and PINs
        Interpreting Button Presses
    Changing State
    Debouncing
        Debounce Example
    AVR Music Box
        The Code
    Boss Button
        Desktop-side Scripting
        Extensions

7. Analog-to-Digital Conversion I
    ADC Hardware Overview
    Light Meter
        The Circuit
        The Code
        ADC Initialization
        Extensions
    Slowscope
        The AVR Code
        The Desktop Code
        Synergies
    AVR Night Light and the Multiplexer
        Multiplexing
        Setting the Mux Bits
        The Circuit
        The Code
    Summary

Part II. Intermediate AVR

8. Hardware Interrupts
    External Interrupts 101: Real-time Button Pressing Examples
        External Interrupt 0 Example
        Pin-Change Interrupt Example
    Capacitive Sensor
        The Sensor
        The Code
        Global, Volatile Variables
        Debugging the Circuit

9. Introduction to the Timer/Counter Hardware
    Timer/Counters: Why and How?
    Test Your Reaction Time
    Using Timer 0 for a Better 8-Bit Organ
    AM Radio
        The Circuit
        CPU Speed
        AM Radio: The Code
    Summary

10. Pulse-Width Modulation
    Bright and Dim LEDs: PWM
    Brute-Force PWM Demo
    Timers PWM Demo
        Initializing Timers for PWM Mode
    PWM on Any Pin
        PWM on Any Pin Demo
    Closing: Alternatives to PWM and a Timer Checklist

11. Driving Servo Motors
    Servos
        The Secret Life of Servos
        The Circuit
        The Code
    Servo Sundial
        The Build
        Ready the Lasers!
        The Code
        Servo Sundial Calibration

12. Analog-to-Digital Conversion II
    Voltage Meter
        The Circuit
        The Code
    The Footstep Detector
        The Circuit
        The Theory
        Exponentially Weighted Moving Averages
        The Code
    Summary

Part III. Advanced AVR Topics

13. Advanced PWM Tricks
    Direct-Digital Synthesis
    Making a Sine Wave
    Next Steps: Mixing and Volume
        Mixing
        Dynamic Volume Control
    Polling USART
    ADSR Envelope
    Auxiliary Files

14. Switches
    Controlling Big Loads: Switches
        Bipolar-Junction Transistors
        MOSFETs
        Power MOSFETs
        Relays
        Triacs and SSRs
        Switches: Summary
    DC Motors

15. Advanced Motors
    Going in Reverse: H-Bridges
    Code: Taking Your H-Bridge Out for a Spin
        Experts-Only H-Bridge
    PWM and the H-Bridge
        Drive Modes: Sign-Magnitude
        Drive Modes: Locked Anti-phase
        Drive Modes: Comparison
    Stepper Motors
    Kinds of Stepper Motors
    Full Stepping and Half Stepping
    Identification of Stepper Motor Wires
        Too Many Wires!
    Dual H-Bridge Chips: The SN754410
    The Code
    Acceleration Control
    Microstepping

16. SPI
    How SPI Works
        Bit Trading Example
        Shift Registers
    EEPROM External Memory
        External Memory
    SPI Demo Hookup
    SPI Demo Code
        SPI EEPROM Library Header
        SPI EEPROM Library C Code
        initSPI
        SPI_tradeByte
        Convenience Functions
    Summary

17. I2C
    How I2C Works
    I2C Demo Hookup
    I2C Demo Library
    I2C Thermometer Demo
    SPI and I2C Data Logger
        Pointers in EEPROM
        The UART Serial Menu
        The Logger’s Event Loop

18. Using Flash Program Memory
    Using Flash Program Memory
        Memory Addresses
        The Address-Of Operator: &
    Pointers
        Pointers in Brief
        Pointers as Arguments to Functions
        Summary
        Optional: Dereferencing Pointers
    Talking Voltmeter
        PROGMEM Data Structures and the Header File
        Sound Playback and Voltage Reading: The .c File
    Generating the Audio Data
        Differential Pulse-Code Modulation
        Encoding Two-bit DPCM
        Encoding DPCM: wave2DPCM.py

19. EEPROM
    Using EEPROM
        Storing in Memory
        Reading from Memory
        Saving and Loading EEPROM
        Organizing Data in EEPROM
    Project: Vigenère Cipher Encoder/Decoder

20. Conclusion, Parting Words, and Encouragement
    Learning AVR: The Missing Chapters
        The Watchdog Timer
        Power Savings
        Crystals and Alternate Clock Sources
        Bootloaders
        Analog Comparator
    Debugging
    Put This Book Down and Build!

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