Transcript Lab #2

Lab 2
EGR 262 – Fundamental Circuits Lab
EGR 262
Fundamental Circuits Lab
Presentation for
Lab #1: Introduction to the Arduino UNO
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Arduino – Historical background
“Arduino started in 2005 as a project for students at the Interaction Design
Institute Ivrea in Ivrea, Italy. Arduino is a single-board microcontroller,
intended to make the application of interactive objects or environments more
accessible. The hardware consists of an open-source hardware board designed
around an 8-bit Atmel AVR microcontroller, or a 32-bit Atmel ARM. Preprogrammed into the on-board microcontroller chip is a boot loader that allows
uploading programs into the microcontroller memory without needing a chip
(device) programmer.
Arduino boards can be purchased pre-assembled or as do-it-yourself kits.
Hardware design information is available for those who would like to assemble
an Arduino by hand. It was estimated in mid-2011 that over 300,000 official
Arduinos had been commercially produced.”
(reference: http://en.wikipedia.org/wiki/Arduino)
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Arduino Microcontroller Boards (www.arduino.cc)
Arduino produces several versions of microcontrollers, including:
Used in EGR 120
and EGR 262
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Arduino Microcontrollers - specifications
Each microcontroller has different specifications. A few specifications for three
of the Arduino microcontrollers are listed below.
Arduino UNO R3
• Atmega 328 8-bit
AMTEL AVR RISC
microprocessor
• 14 digital I/O pins
• 6 PWM digital I/O pins
• 6 analog I/O pins
• 16 MHz clock speed
• 32 kB flash memory for
storage of code
• $28.49
Arduino Mega 2560 R3
• Atmega 2560 8-bit
AMTEL AVR RISC
microprocessor
• 54 digital I/O pins
• 14 PWM digital I/O pins
• 16 analog I/O pins
• 16 MHz clock speed
• 256 kB flash memory for
storage of code
• $55.56
Arduino DUE
• AT91SAM3X8E 32- bit
ARM Cortex-M3
microprocessor
• 54 digital I/O pins
• 12 PWM digital I/O pins
• 12 analog I/O pins
• 84 MHz clock speed
• 512 kB flash memory for
storage of code
• $55.56
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References: (many more available)
1) Arduino web site (software, microcontrollers, tutorials, examples, etc) - www.arduino.cc/
2) Arduino Tutorials - http://www.ladyada.net/learn/arduino/
3) Engadget (gadgets built using Arduinos) - http://www.engadget.com/tag/Arduino/
4) Instructables (gadgets using Arduinos) - http://www.instructables.com/id/Arduino-Projects/
5) EGR 120 Arduino-BOT Lectures #1-5 - http://faculty.tcc.edu/PGordy/Egr120/
6) TCC Library – Free Safari eBooks – You can access eBooks as follows:
• Go to TCC’s home page and select Library
• Select Library Catalog – eBooks
• Select Safari Tech Books
• Log in (usual ID and password)
• Search for Arduino – Here are a few that I found:
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Powering the Arduino UNO The Arduino can be powered using:
1) USB cable (5V input) – OK for downloading and testing programs, but not
for driving external circuits. Provides a weak 5V to the Arduino board
2) AC to DC Adaptor (recommended 9 to 12V DC, 250mA or more, 2.1mm plug,
centre pin positive)
3) DC Power Supply (7V – 12V recommended, 6V – 20V limits)
4) 4 AA Batteries ( ≈ 6V input) - Provides a weak 5V to the Arduino board
5) 5 AA Batteries (≈ 7.5V input)
Note: If both the USB and another source (AC/DC adapter, batteries, etc) are
connected, the Arduino will select the stronger source.
Typical Arduino UNO voltages:
Connection
USB
4 AA Batteries
5 AA Batteries,
AC/DC Adaptor or
DC Power Supply
5V
4.28 V
4.92 V
4.98 V
3.3 V
3.20 V
3.29 V
3.29 V
Servo Port *
4.28 V
4.92 V
4.98 V
Vin
4.32 V
5.51 V
7.09 V
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Powering the Arduino-BOT We will typically power the Arduino with an
AC/DC adaptor. You can leave both the USB and the AC/DC adaptor
connected and the Arduino will use the higher adaptor voltage. We will make
5V and GND (ground) connections to the breadboard as shown below.
USB
AC/DC
Adaptor
Plug
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6 of the 14 are also PWM (8-bit
AREF (Analog reference) –
Pulse Width Modulation) pins:
used to set the max analog
~11, ~10, ~9, ~6, ~5, ~3
input value
14 Digital I/O
LED connected to
Pins (D0-D13)
D13 for testing
Header (for
22 gauge wire)
Reset button
ICSP header for
communication
USB
with peripheral
16 MHz crystal
devices
oscillator
Arduino UNO
Hardware
Specifications
Voltage regulator
DC Input (7V – 12V)
Reset – LOW voltage
resets the microcontroller
(same as pressing the
reset button)
ATMega328
microprocessor
3.3V, 5V, GND (ground)
and Vin (unregulated input, such as
12V from an AC/DC Adaptor
6 Analog
I/O Pins
(A0-A5)
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Arduino UNO Schematic (2 equivalent versions)
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The Arduino Programming Environment
• The Arduino software (Arduino 1.05 or later) is available on lab computers and can
also be downloaded from http://arduino.cc
• The software requires no installation and can even be launched from a flash drive.
• Open using the shortcut on the desktop or double-click Arduino
in the Arduino-1.0.5 folder as indicated below
• The file opened is referred to as a “sketch” and will be automatically named using
the date. You can rename it if you wish. The file below is named sketch_jan20a.ino
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Notes:
The Arduino Programming Environment
• Verify is used to compile your program
The Arduino software is based on C/C++.
(or sketch). (It checks for errors).
Note that the instructions are case-sensitive.
C++ is not line-oriented, so a semicolon (;) is needed • Upload is used to send the program
(sketch) to the Arduino via the USB
to indicated the end of an instruction.
cable.
• Arduino programs have two main parts:
1. setup – a function to initialize items
or to perform operations one time.
2. loop – a function with commands
that will be repeated indefinitely
• Serial.begin(baud rate) is used to
establish serial communications
between the Arduino and the computer.
Data is transmitted at 9600 baud
(bits/second). Note that Serial uses
digital pins 0 and 1 so they cannot be
used for other inputs/outputs.
• Serial.print(text, values, or variables)
is display information from the
Arduino-BOT on the display window.
• Select Serial Monitor to open a
window to view printed messages from
the Arduino.
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More on functions
Functions in C/C++ have a particular structure as indicated below for the setup
function.
• Functions execute a series of statements contained within curly braces.
• Functions begin with a particular form:
return_type function_name (parameter_list)
In the case above, the return_type is void (no output), the function_name is
setup, and the parameter_list (typically inputs) is empty.
• Both statements in the body of the setup function are calls to functions in
Arduino’s Serial library. We will introduce more useful functions as we
continue in this course.
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Want more information?
For more info on the Arduino programming
language, select Help – Reference.
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Example – Printing a message repeatedly
The previous program was modified. The Serial.print(“Hello!”) instruction was moved
into the loop function. Now it will be written to the output screen repeatedly.
Notes:
•
•
•
•
The following instruction causes
a delay of 1000 ms or 1 second.
delay(1000);
Hello! is now printed to the
display window once per second.
If we want each Hello! statement
printed on a new line, we can
used the following command:
Serial.println(“Hello!”)
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Controlling Lights (LEDs) with the Arduino
In our first lab we will control lights (LEDs) using the Arduino. Some new commands
need to be introduced first.
pinMode( )
Recall that the Arduino has 14 Digital I/O pins. They can be configured as inputs or
outputs using the pinMode( ) command.
Examples:
pinMode(4, OUTPUT);
// Make pin 4 an output
pinMode(4, INPUT);
// Make pin 5 an input
digitalWrite( )
Once a pin has been configured as an output, it can be set HIGH (5V) or LOW (0V)
using the digitalWrite( ) command.
Examples:
pinMode(4, OUTPUT);
// Make pin 4 an output
digitalWrite(4, HIGH);
// Make pin 4 HIGH
digitalWrite(4, LOW);
// Make pin 4 LOW
Note: Generally avoid using pins 0 and 1 as they are used for serial communication and
avoid pin 13 as it is tied to a test LED on the Arduino and may blink during startup.
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delay( ) and delayMicroseconds( N)
If an LED is to be turned on for a certain period of time, one method would be to:
1) Turn it ON
2) Wait for the specified period of time using delay( ) or delayMicroseconds( )
3) Turn it OFF
delay( N)
Pause the program for N milliseconds
Example:
delay(25);
// Pause for 25 ms
delay(4000);
// Pause for 4 s
delayMicroseconds( N)
Pause the program for N microseconds
Example:
delayMicroseconds(25);
delayMicroseconds(4000);
// Pause for 25 us
// Pause for 4 ms - same as delay(4)
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Sample program – The program below will blink the LED connected to digital pin 4
once per second (0.5 s ON and 0.5 s OFF).
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Variables and loops – Suppose that we wanted to blink an LED a certain
number of times? To do this we need to see how to declare variables in C++
and to form loops.
Declaring variables in C++:
We will consider three types of variables:
int – used to declare integer variables (ranging from -32768 to 32767)
float – used to declare floating point variables (values with a decimal point)
char – used to declare character variables (single symbols within single quotes)
Examples:
int a,b,c;
a = 25;
int d = -21;
char c = ‘m’;
float g =-9.81
// declare integer variables
// assign value to integer variable
// declare and assign value
// declare character variable and assign value
// declare floating point variable and assign value
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Using variables with the Arduino
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for loop in C++:
Several types of looping structures can be used in C++. The for loop is especially
useful when you want to execute instructions in the loop a specific number of times.
See the example below.
Form: for (initialization; condition; increment)
{
// body of loop
}
Note:
C++ sometimes uses shortcut
operators to increment, decrement, or
change variables in loops.
i++
means add one to i
j-means to subtract one from j
k+=2 means add 2 to k
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Blinking an LED a specific number of times
The program below can be used to blink an LED (on digital pin 12) 10 times.
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Comments
Comments are an important part to computer programs.
Comments allow you to explain your code to someone reading or using the code.
// is used to indicated a comment in C++
Tips for good comments:
• Do not explain how C++ works. Explain how you are using the code.
Example:
digitalWrite(12, HIGH);
// make digital pin 12 HIGH
(Weak comment. Why are you making it HIGH?)
digitalWrite(12, HIGH);
// turn on LED on pin 12
(Good comment)
• Explain similar instructions only once.
Example:
digitalWrite(12, HIGH); // turn on LED (pin 12)
delay(500);
// wait 500 ms = 0.5 s
digitalWrite(12, LOW); // turn off LED (pin 12)
delay(500);
// wait 500 ms = 0.5 s (unnecessary comment - repeated)
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Comments
In addition to using comments throughout programs, begin all programs for this course
with an initial block of comments. Example:
Initial block
of comments
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Adding additional functions to a sketch
The Arduino programs (sketches) written so far have included two key
functions: setup( ) and loop( ). Programs can also have additional functions.
Functions are particularly useful when you are likely to repeat sections of code.
Example: Write
a program that
uses a function to
cause an LED on
pin 4 to blink N
times.
Note that a
prototype was not
required for the
function.