bascom-avr-theory.pdf

An Introduction to

Microcontrollers and

Software Design

Name _____________________

MRGS Technology Electronics

Available online from www.techideas.co.nz

B. Collis - Mount Roskill Grammar School 2003-2009

This work is licensed under the Creative Commons Attribution-Non-commercial-Share Alike 3.0 License. To view a copy of this license, visit

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Table of Contents

Introduction to Microcontroller Electronics .......................................................................4

What exactly is a Microcontroller .............................................................................6

What you do when learning to program ...........................................................................7

Achievement Objectives from the NZ Curriculum ....................................................8

Hardware - The AVR Microcontroller ...............................................................................9

Power Supplies ........................................................................................................9

AVR Programming .................................................................................................10

Breadboard ............................................................................................................10

Simple AVR circuit .................................................................................................11

Circuit description ..................................................................................................12

AVR programming cable ........................................................................................12

Introduction to writing programs using Bascom-AVR IDE ..............................................13

Reading and Writing using flowcharts....................................................................14

Input and Output Control........................................................................................15

Sending Morse code ..............................................................................................16

Microcontroller ports: write a Knightrider program using 8 LED’s ..........................17

Multiple LEDs - Traffic lights exercise ....................................................................18

Multiple LEDs - 7 Segment Displays......................................................................19

Different types of switches .....................................................................................20

First input device – a single push button switch .....................................................21

BASCOM and AVR Assignment ............................................................................23

Words you need to be able to use correctly when talking about programming ......24

A Bit about Numbers..............................................................................................25

Programming Codes of Practice ....................................................................................26

Programming Template .........................................................................................27

Variables................................................................................................................28

The BASCOM-AVR Simulator................................................................................29

Control statements – IF THEN .......................................................................................31

Connecting and programming multiple switches....................................................31

Reading multiple switches in software ...................................................................32

Using flowcharts to help solve problems................................................................33

Using IF-THEN to control which parts of a program happen..................................37

Debounce ..............................................................................................................36

More Interfacing .............................................................................................................38

Analogue to Digital Conversion..............................................................................39

Reading an LDR’s values in Bascom.....................................................................41

Temperature measurement using the LM35 ..........................................................43

Keypad Interfacing .................................................................................................44

Alternative keypad interface...................................................................................44

Controlling high power loads (outputs)...................................................................45

Parallel Data Communications...............................................................................46

LCDs (Liquid Crystal Displays) ..............................................................................47

Connecting an LCD to a 40pin AVR.......................................................................48

Don’t delay .............................................................................................................51

Programs as solutions: understanding algorithms and flowcharts .................................54

Planning Sequence for an AVR project..................................................................54

One Page Brief ......................................................................................................55

One Page Brief ......................................................................................................56

Algorithm Development Worksheet........................................................................57

Example Brief.........................................................................................................58

Algorithm Planning Example ..................................................................................59

Example Brief.........................................................................................................60

Computers and Microcontrollers ..............................................................................5

Glue Gun Timer Flowchart .....................................................................................62

Multiplication Algorithms ........................................................................................64

Algorithm exercises................................................................................................68

LCD programming exercises..................................................................................69

Scrolling Message Assignment ..............................................................................70

Strings Assignment ................................................................................................71

ASCII Character Table...........................................................................................73

ASCII Assignment..................................................................................................74

Time.......................................................................................................................77

Sounding Off ..........................................................................................................81

System and Software Design.........................................................................................84

Understanding how simple systems work ..............................................................84

Problem Decomposition Example ..........................................................................85

Statecharts.............................................................................................................87

Token Game – Statechart Design Example ...........................................................90

Serial Communications ..................................................................................................95

RS 232 Serial Communications .............................................................................97

Serial IO using Inkey() .........................................................................................102

Introduction to I2C................................................................................................103

Real Time Clocks.................................................................................................105

DS1307 RTC........................................................................................................107

Arrays ..........................................................................................................................112

Computer Programming detail .....................................................................................115

AVR Internals – how the microcontroller works....................................................116

Interrupts......................................................................................................................120

Polling versus interrupt driven architecture ..........................................................122

Timer/Counters ............................................................................................................123

PWM - Pulse Width Modulation ...........................................................................126

AVR Clock/Oscillator............................................................................................129

Assignment – Maths In The Real World.......................................................................130

Math Assignment - Part 1 ....................................................................................133

Math Assignment - Part 2 ....................................................................................134

Math Assignment - Part 3 ....................................................................................135

Math Assignment - Part 4 ....................................................................................136

Math Assignment - Part 5 ....................................................................................137

Math Assignment - Part 6 ....................................................................................138

Bascom Keyword Reference................................................................................139

AVR Development Boards we can use ........................................................................141

AVR Development Board 2 ..................................................................................144

ATMEGA Development Board 3 ..........................................................................147

ATMEGA16/32 Microcontroller Pin Functions and Connections..........................149

ATMEGA16/32 40pin DIP package– Pin Connections.........................................150

iii

Algorithm Development Example...........................................................................61

Introduction to Microcontroller Electronics

The course is an introductory course for students in design using microcontrollers; it covers both

hardware interfacing and software design.

Microcontrollers are a common electronic building block used for many solutions to needs throughout

industry, commerce and everyday life.

They are found inside aircraft instruments.

They are used extensively within cellular phones, modern

cars,

domestic appliances such as stereos and washing machines

and in automated processes through out industry

Computers and Microcontrollers

A microcontroller is very much everything that you would find inside a PC's case, but on a

smaller scale. There is a processor, temporary memory for data (the RAM) and memory for

programs (the ROM).

However don't think that because a microcontroller is smaller than a PC that it is the same

comparison as between a real car and a toy car. The microcontroller is capable of carrying

out millions of instructions every second. And there are billions of these controllers out there

in the world doing just that. You will find them inside cars, stereos, calculators, remote

controls, airplanes, radios, microwaves, washing machines, industrial equipment and so on.

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