- •Chapter 1: Introduction
- •Goals
- •Chapter 2: Quick Start Guide
- •Software
- •WinAVR – Oh, Whenever…
- •Programmers Notepad
- •AVRStudio – FREE and darn well worth it.
- •Br@y++ Terminal:
- •Hardware
- •Constructing Your Development Platform
- •Blinking LEDs – Your First C Program
- •Write it in Programmers Notepad
- •Download to the Butterfly with AVRStudio
- •Blinky Goes Live
- •Simulation with AVRStudio
- •GOOD GRIEF!
- •Comments
- •Include Files
- •Expressions, Statements, and Blocks
- •Operators
- •Flow Control
- •Functions
- •The Main() Thing
- •Chapter 4: C Types, Operators, and Expressions
- •Data Types and Sizes
- •Seen on a shirt at a Robothon event:
- •Bits
- •Bytes
- •The long and short of it
- •Variable Names
- •Constants
- •Declarations
- •Arithmetic Operators
- •Relational and Logical Operators
- •Bitwise Operators
- •Testing Bits
- •Assignment Operators and Expressions
- •Conditional Expressions
- •Precedence and Order of Evaluation
- •Projects
- •Port Input and Output
- •Cylon Eye Speed and Polarity Control
- •Chapter 5: C Control Flow
- •Statements and Blocks
- •If-Else and Else-If
- •Switch
- •Loops – While, For and Do-while
- •Break and Continue
- •Goto and Labels
- •A few practical examples: strlen, atoi, itoa, reverse
- •Chapter 6: C Functions and Program Structures
- •Function Basics
- •Returns
- •Variables External, Static, and Register
- •Scope
- •Headers
- •Blocks
- •Initialization
- •Recursion
- •Preprocessor
- •Macro Substitution
- •Conditional Inclusion
- •Projects
- •Is anybody out there? Communicating with a PC
- •Demonstrator
- •PC_Comm
- •Using CommDemo:
- •Chapter 7: Microcontroller Interrupts and Timers
- •Interrupts
- •Projects
- •Grab your joystick – and test your interrupts
- •Using joystick
- •Timers/Counters
- •Calibrating the Butterfly oscillator:
- •OSCCAL_calibration() function – detailed explanation
- •ALL THIS AND WE HAVEN’T EVEN STARTED CALIBRATING YET!
- •Projects
- •Precision Blinking
- •Using Precision Blinking:
- •Pulse Width Modulation – LED Brightness Control
- •Pulse Width Modulation - Motor Speed Control
- •Speedometer
- •Chapter 8: C Pointers and Arrays
- •Addresses of variables
- •Function Arguments
- •Arrays
- •FIFOs and LIFOs: Stacks and Queues (Circular Buffers)
- •Stacks
- •Queues (Circular Buffers)
- •Function Pointers
- •Complex Pointer and Array Algorithms
- •Projects
- •Messenger
- •Arrays in RAM and ROM
- •Does anybody know what time it is? A Real Time Clock.
- •A one second interrupt
- •Converting Computer Time to Human Readable Time
- •The Real Timer Clock Software
- •Music to my ears. “Play it again Sam.”
- •More on pointers to arrays
- •Setting the frequency
- •Setting the duration
- •An example song array – Fur Elise
- •Using the Piezo-element to make sound
- •Initializing the Timer1 for PWM to the piezo-element.
- •Generating the tone using PWM from Timer1
- •Using the Timer0 interrupt to play a tune
- •Chapter 9 – Digital Meets Analog – ADC and DAC
- •But First - A Debugging Tale
- •Analog to Digital Conversion
- •What is Analog to Digital Conversion?
- •Analog to Digital Conversion by Successive Approximation
- •Analog to Digital Conversion with the ATMEGA169
- •Starting a Conversion
- •Conversion Timing
- •Changing Channels
- •Digital Noise Reduction
- •Conditioning the Analog Input Signal
- •Accuracy
- •Projects
- •Initializing the ADC
- •Reading the ADC
- •Light Meter
- •Temperature Meter
- •The @#%#&*#!!!! Volt Meter
- •Using ADC
- •DAC and ADC - Function Generator / Digital Oscilloscope
- •Chapter 10: C Structures
- •Structure Basics
- •Structures and Functions
- •Structure Arrays
- •Typedef
- •Unions
- •Bit-fields
- •Bit-Fields the C-way
- •Bit-fields the masking-way
- •Projects
- •Finite State Machine
- •Chapter 11 The Butterfly LCD
- •PC to LCD test program
- •Conclusion
- •Appendix 1: Project Kits
- •Data I/O
- •PWM Motor Control
- •Appendix 2: Soldering Tutorial
- •Appendix 3: Debugging Tale
- •Appendix 4: ASCII Table
- •Appendix 5: Decimal, Hexadecimal, and Binary
- •Appendix 6: Motor Speed Control Wheel
- •Appendix 7: HyperTerminal
- •Index
Chapter 9 – Digital Meets Analog – ADC and DAC
•Timer/Counter 1 Capture Event
Conversion Timing
The successive approximations are clocked between 50kHz and 200kHz to get the maximum resolution. You can use higher sampling rate frequencies, but you get lower resolution. The sampling rate is determined by the input clock and by a prescaler value set in the ADPS bits of the ADCSRA register. The first conversion takes 25 clock cycles to initialize the hardware. Normal conversions take 13 clock cycles and auto triggered conversions take 13.5.
Changing Channels
There are some complexities involved in changing channels and voltage references that lead to the recommendation that you always wait till a conversion is complete before making a change. If this is inconvenient, read the data book and figure it out yourself.
Digital Noise Reduction
The CPU and I/O peripherals can generate a lot of electrical noise that affect the accuracy of the ADC. We can put the system to sleep to shut it up and then take our ADC readings in the quietened environment. Details in the data book.
Conditioning the Analog Input Signal
The accuracy of the conversion will depend on the quality of the input signal. A few recommendations:
•Filter out signal components higher than the Nyquist sampling frequency (double the frequency of interest) with a low pass filter.
•Sampling time depends on the time needed to charge the sample and hold circuit so always use a source with an output impedance of 10 kOhm or less.
•Use only slowly varying signals.
•Keep analog signal paths as short as possible.
•Use the ADC noise canceller function.
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Chapter 9 – Digital Meets Analog – ADC and DAC
•If any of the ADC port pins are used for digital output, don’t switch them while a conversion is going on.
Accuracy
The data book has some cursory discussion of the extremely dense topic of ADC accuracy. Just be aware that in the accompanying project we don’t use any of these recommendations, so take the accuracy of our measurements with a grain of salt.
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