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 http://creativecommons.org/licenses/by-nc-sa/3.0 . The licensor permits others to copy, distribute and transmit the work. In return, licensees may not use the work for commercial purposes — unless they get the licensor's permission. The licensor permits others to distribute derivative works only under a license identical to the one that governs the licensor's work. Table of Contents Introduction to Microcontroller Electronics .......................................................................4 Computers and Microcontrollers ..............................................................................5 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 ii Algorithm Development Example...........................................................................61 Glue Gun Timer Flowchart.....................................................................................62 Multiplication Algorithms ........................................................................................64 Algorithm exercises................................................................................................68 LCD programming exercises..................................................................................69 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