Studio 0: Introduction to Arduino

• Access your repository
  • Introduction to Arduino
    • Assembling the Arduino Board
    • Programming the Arduino
  • Today’s studio
    • Objectives
  • Setting up Arduino
    • Getting ready
    • Running a program
      • Problems uploading?
  • Timing in Arduino
  • Digital output in Arduino
  • Timing in Java
  • Comparison
  • Finishing up
  • Key Concepts

Access your repository

We will be using git to distribute the code you need for studios and assignments. You will also use git to turn in your work. Here’s a great video that explains what git is and how it works:

Before you can complete any of the assignments, you must set up your repository. You can find instructions on how to do this here.

The link to access Studio 0 is here. Read the guide before clicking this link!

Introduction to Arduino

The Arduino is a (very) small computer that has dramatically fewer capabilities than the desktop or laptop machines that you have used in the past to run Java programs. For example, it doesn’t have a keyboard, it doesn’t have a screen, its processor is well over 100 times slower, and you might even be wondering, “what is the point?” The point is that small computers like the Arduino are priced relative to their capabilities. Want a computer for under \$10? If so, the Arduino is a great choice! Its small size makes it incredibly useful for lots of jobs where it would seem overkill to use a $1500 laptop. Over the course of the semester, we’ll discover all that the Arduino can do, even though it starts out as humbly as it does.

Assembling the Arduino Board

Today you will need to assemble your the main components of your Arduino kit:

The Arduino RedBoard:

The BreadboardHolder:

And the (solderless) Breadboard:

When done, it should look like:

You will need to:

1. Attach the Breadboard to the Breadboard holder with the labels on the breadboard facing the correct way, as shown above. The breadboard has an adhesive backing. Remove the protective layer and stick it to the holder in the indentation. The column letters a-j on the top and bottom of the breadboard should be in the same direction as the “sparkfun” label on the breadboard holder.

2. Put the RedBoard on the Breadboard Holder. Again, the print/labels should match those shown above. The Redboard has four holes for screws and the kit includes two screws. Any two holes will be suitable, but diagonal holes are recommended. Screwdrivers are available from the instructors and TAs.

Programming the Arduino

Although the Arduino itself is a computer separate from your laptop or desktop, its lack of screen serves as an impediment to programming it directly. We write and compile programs for it on a larger computer and then send them over to the Arduino via USB. The Arduino, as you’ll soon see, runs one program at a time, for as long as it’s plugged in.

As you might imagine, the transfer process is very complex, and until the Arduino came out in 2005, microprocessor programming was a long and arduous task. Luckily for us, we are past those dark ages of computing and we have the Arduino IDE (Integrated Development Environment). You may be familiar with the Eclipse IDE, which we use in CSE 131 to write and compile Java programs. The Arduino IDE helps you write and compile Arduino programs and also manages uploading those programs to your Arduino board.

Arduino programs, however, are not written in Java. They are written in a variant of C, one with extra libraries specifically for writing Arduino programs. Since you have already been introduced to C, programming the Arduino should be a snap.

Today’s studio

Today you will get accustomed to the basics of Arduino C by writing a simple “heartbeat” program and uploading it to your Arduino board.

Then you will write an identical program in Java and compare the two programs to understand the differences between the two systems.

Objectives

By the end of studio, you should know:

• how to structure a basic Arduino program,
• how to use the Arduino reference guide,
• how to communicate with your Arduino, and
• how to use Arduino digital output pins.

Onward!

Setting up Arduino

Getting ready

First, you need to check out your repository so that you can commit the changes you make today. You may also need to tweak Arduino’s preferences to make it easier to use.

1. Organize around one computer, using the large screens on the walls to make things easier if you need.

2. Open Eclipse. (If you haven’t already installed Eclipse, see the instructions here)

   Make sure to note where your Eclipse workspace is located. You will need it.

   If you don’t know, File>Switch Workplace>Other... will show you. Press Cancel if you don’t want to change it.

3. Make the font size bigger if necessary.
4. Check out your repository.

In CSE132 this semester, we will be using Git as our version control system. We have made a git Tutorial to get your workspace set up and running.

Make a note of the Local Destination directory, as it will be needed later.

Running a program

In Eclipse nagivate to the studios.studio0 helloworld.ino file. If the icon shows the Arduino icon (blue/green circle with a white infinity symbol), double click on the file. If not, right click on the file name and select Open With > Other... and select the Arduino application (called Arduino file on Windows systems).

The helloworld.ino file is a complete Arduino program. Compiling and uploading it should help you learn the Arduino interface.

1. Click the Upload button to compile helloworld and upload it to the Arduino (the Verify button just compiles your program, looking for errors in the code).
2. Make sure the code uploaded correctly (the status message should say Done uploading.).
3. Open the Serial Monitor to view the output that our newly programmed Arduino writes to its serial port. You should see the phrase Hello, world!.
4. Press the reset button on your Arduino board. The Serial Monitor should display the phrase Hello, world! again.

5. The Arduino has two entry points into your code, or, in other words, two places it looks to run your code. Whenever the Arduino starts up or is reset, the Arduino runs the void setup() function once. After that, the Arduino runs the void loop() function over and over until the Arduino is unplugged or reset.

   Opening serial monitor or pushing the reset button on the Arduino both reset the Arduino.

   Note that opening the serial monitor will sometimes print garbage data as the signals between the Arduino and computer sync up.

Timing in Arduino

Now you’ll write your own Arduino program in C.

1. Take a quick look at the Arduino reference. It should be surprisingly similar to Java.

   Pay special attention to the Serial library (under Communication in the Functions section) and the delay() function.

2. Author a program called heartbeat in the studio0 folder (so the heartbeat.ino file should be in studio0/heartbeat/) that, once per second, prints:

    <n> sec have elapsed
   

   where <n> is the number of seconds that have passed since the program was reset. The delay() function will come in handy, as will Serial.print() and Serial.println().

   Note that C strings work differently than Java strings (namely string + string does not exist in C, and Arduino C does not support printf()), so you’ll need to work around that. The Arduino reference page on strings explains the C implementation in more detail.

3. Verify that your newly authored program is functioning at least approximately correctly.

Digital output in Arduino

The program you just wrote could easily be a Java program on your laptop (as it will soon be), and does not show off the power of the Arduino. We’ll add a flashing light to show off the critical feature of the Arduino: it can interface with everyday electrical circuits.

1. You probably noticed the numbered holes on each side of the Arduino. We call these pins. The Arduino code you create can read and write electrical signals from these pins: they can turn on and off lights (as we will do today), read whether or not a button is pressed, or determine how far a knob is turned, as long as you wire up the correct circuit.

   Circuits are hard, so we will use pin 13 because it is already attached to an LED on the Arduino body itself, and so requires no wiring on your part. Later, we will walk through attaching your own LED to pin 13. This code will power it just the same.

2. In your setup() function, ensure pin 13 is ready to write by setting its pinMode() to OUTPUT. Look at the Arduino reference explains the C implementation in more detail. for pinMode() to learn how.

3. Modify your loop() to blink the LED every second, just before it Serial.print()s. You will need to divide your loop into two delay()s—one where the LED is on, and one where the LED is off.

   You can turn the LED on and off by turning on and off the pin it’s attached to. In computer science terms, you write HIGH or LOW to the pin. The aptly named digitalWrite() function will help you do this. Check the Arduino reference to see how this function works.

4. Make sure your program still beats approximately once a second.

Timing in Java

Now write the earlier timing program in Java.

1. Create a new class Heartbeat in the studio0 package. Make sure you include a public static void main(String[] args) method so that your new class can be a standalone Java program. You can do this within the New Java Class wizard.
2. Your Heartbeat program should print a message to console once per second. Use Thread.sleep() to measure the passage of time, as described in class. Remember that Thread.sleep() can throw an exception, and you should use try {} catch() {} blocks to catch any exceptions.
3. Verify the program works reasonably.

Comparison

Now compare how good your Arduino is at keeping time compared to your desktop or laptop.

1. Start up both programs and observe how long it takes to start drifting in time relative to one another. Make note of this to tell your TA during checkout.
2. Add some code to your Arduino program that displays the return value from the millis() function. How many milliseconds should elapse every iteration? What do you actually see? What does this imply about the reliability of timing using delay()?

Finishing up

Check out and get out.

1. Make sure to commit your workspace

   In Eclipse’s package explorer, any files you have modified since your last commit are prefixed with a >.

   If you have saved some files from the Arduino IDE, they might not yet appear in the navigation pane of Eclipse. Right-click on your repo and choose Refresh and they should show up.

   Right-click the outer-most folder (you want to commit everything within), and choose Team>Commit.... Write a helpful message and press Commit and Push.

   You can verify that your changes went to the server by going to your GitHub page for your repository. Click the “Source” link on the left side of the page and make sure your file exists with the code that you wrote.

2. Show your two timing programs and your repository to a TA.
3. Tell your TA how long it took for your Arduino and computer to get out of sync.

Repository structure for this lab:

Key Concepts

• Arduino
  • Navigating the Arduino IDE
  • Using LEDs
  • Timed LED blinks
    • delay()
  • Sketchbook location
  • Uploading Problems
• Java / PC
  • Eclipse workspace setup
  • Timed printing
  • Committing with Eclipse
• Reliability of Timing
  • PC vs Arduino
  • delay()