Lab 2_ Programming an Arduino.pdf

Joseph Patton
ECE 198
Lab 2: Programming an Arduino
Complete Goal: To program the Arduino to blink an LED. This lab will provide the skills
necessary to write a simple Arduino program that accesses the general purpose
input/output (GPIO) pins. These pins can be used to acquire data in the form of digital
and analog voltages. These pins can also be used to control various devices in the form
of driving the pins to high or low voltages, as will be seen in this lab.
Materials Needed:
1x Arduino Uno
1x Raspberry Pi Zero W with power supply
1x USB-A to USB-B cable
2x Micro-USB to USB-A adaptor
1x HDMI cable and adaptor
1x Wireless Keyboard and mouse
On Arduino: Arduino boards feature an Atmel 8-bit AVR microcontroller (Our boards
have an ATMEGA 328P). These microcontrollers are pre-programmed with a boot
loader that makes it easy to upload programs to the flash memory on the chip. Arduino
programs can be written in any language with compilers that produce binaries for the
target processor. In this case, we will be using a C/C++ because it is supported by the
Arduino Interactive Development Environment (IDE). A program written in the Arduino
IDE is called a ‘sketch’. A basic sketch consists of two functions: setup() and loop(). The
setup function is called first in the sketch, and is used to create variables,to choose pin
inputs and pin outputs, and to set other values needed in the sketch. The loop function
is called after the setup function, and runs repeatedly until the board is reset or powered
off. The loop function is used to do anything that happens perpetually, such as
gathering data. (Or in this case blinking an LED). We will use simple pre-written
functions from the Arduino libraries to complete this lab.
ON LED ‘L’: On the face of the Arduino there is an LED labelled ‘L’. This is the LED that
we are going to be blinking. This LED is in series with pin 13, so if the pin is driven to a
high voltage, the LED lights up.

Powering On The Arduino:
1. Power on and log into your Raspberry PI. Plug your Arduino into your Pi.
2. Start the Arduino IDE.
3. Start a new sketch and name it “ledBlink”.
4. Under the Tools pulldown, select your board as an Arduino UNO, select the
appropriate serial port (probably /dev/ttyACM0 or /dev/ttyACM1), and select your
programmer as the AVRISP mkII.
Writing the Program
1. To begin out program, we will set up a definition. Instead of writing out the
number ‘13’ every time we want to access PIN 13, we will write a preprocessor
directive that defines LED as 13. A preprocessor directive is examined by the
preprocessor before compiling. The statement #define LED 13 tells the
preprocessor to find and replace every instance of ‘LED’ in the program with ‘13’.
This makes for a more easily-understood program.
#define LED 13
2. The next step is to insert our setup() and loop() functions.
#define LED 13
void setup()
{
}
void loop()
{
}

3. In our setup function, we need to set pin 13 as an output. Once pin 13 is set as
an output, it will be able to drive our LED. To set this pin as an output, we will call
the pinMode() function from the Arduino library. This library is automatically
included in your program when you use the Arduino IDE. To call the pinMode
function, we simply pass it the pin we want to set, and then the mode that we
want to set it to. For this lab, we are setting pin 13 as an output. Luckily we
defined LED as pin 13, so we can pass LED as the first argument and the
compiler will know that we mean pin 13.
#define LED 13
void setup()
{
pinMode(LED, OUTPUT);
}
void loop()
{
}
4. Once we have set LED as an output, we can write the code to blink the LED. To
achieve a blinking LED, we need to drive it high for a period, then low for a
period, then repeat. This can be accomplished in the loop() function, which will
run over and over again until the board is powered down. To change the output
of a pin, the digitalWrite function is called. As arguments, this function takes the
pin number that you wish to change the state of and the state that you wish to
change it to. To change LED to an output, we simply call digitalWrite(LED,
HIGH).

#define LED 13
void setup()
{
}
void loop()
{
digitalWrite(LED, HIGH);
}
5. Now that the pin LED is high, the LED will light up. To blink the LED, we also
need to set it low again with digitalWrite(LED, LOW). Although, if we simply set
the pin high and then low, the state will change back and forth too fast for us to
see. This is not the objective. To produce a slower blink, the delay() function
must be called. The delay function stops the execution of the program for a
certain number of milliseconds. To make the program wait for a second, call
delay(1000).
#define LED 13
void setup()
{
}
void loop()
{
digitalWrite(LED, HIGH);
delay(1000);
digitalWrite(LED, LOW);
delay(1000);
}
6. Our loop function now sets the LED high, waits 1 second, sets the LED low, waits
one second, and repeats. This is the desired objective.

Programming the Board:
1. First save the program with Ctrl + S. To compile the program, press Ctrl + R, or
click the checkmark button. To upload the sketch, press Ctrl + U, or press the
forward arrow button. If both of these succeed, the program should be uploaded
to your board, and LED ‘L’ should be blinking.

Lab 2_ Programming an Arduino.pdf

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Lab 2_ Programming an Arduino.pdf