Introduction to programming using Arduino

Introduction

Requirements

• Laptop computer (Mac OS X, Windows, Linux)
• Arduino microcontroller and USB cable
• Arduino environment installed - Go here for download links Arduino IDE

Overview of this guide

• How a computer (or microcontroller like the Arduino) work
• Human languages versus computer languages
• Input/Output
• Arduino basic program layout
• Compilation and Deployment
• Comments
• Boolean logic
• Logic structure (if) and
• Strings and numbers representation
• Variables and datatypes
• Subroutine and functions
• Libraries

How Computers Work

• Computers process instructions (also called programs or code).
  • This code has to be precise.
  • Computers can process many instructions very quickly.
  • How quickly? Even these little Arduinos can run 16 million instructions every second!
  • We will program in a high level language. This is more powerful, but slower. (Still very fast!)

• Memory is where we store instructions and data. There are 3 types of memory.
• Input is where we acquire data
• Output is where we send data or control a device
• Compiling is converting the instructions from human readable text format to machine readable binary
• Uploading is loading this binary code into the Arduino

• Some programming terms:

   Comments
   Datatypes 
   Boolean logic
   Strings and numbers representation
   Variables
   Logic structure (if) (there are others we will get to as well)
   Subroutine and functions
   Libraries 

Arduinos

Safety Notice

• Watch out - sharp bits
• Take care when connected - don't short on metal or wires...
• Static care

Intro to Arduino GUI Software

See Arduino IDE for pictures.

• Compiling
• Uploading
• Help - reference

The Bare Minimum Arduino Program

You can find all of these examples inside the Arduino IDE.

• Arduino IDE > File > Examples > Basics > BareMinimum.

This program does... nothing! But it will compile and it will run.

/*
 * My first program
 */
void setup() 
  {
  // put your setup code here, to run once
  }

void loop() 
  {
  // put your main code here, to run repeatedly
  }

CONCEPT: Functions:

• SETUP is a function that is always run once
• LOOP is a function that is run over and over

Functions are the same as mathematical functions

• For example: sin(x) is a function that takes a number x and returns the sin value of it.
• The empty parenthesis () means that it does not take any parameters
• VOID means that it does not return anything

CONCEPT: Comments

• Comments are there to help the programmer document (explain) his own code.
• Comments are ignored by the computer.
• Lines block that start with /* and end with */ are multiline comments
• Lines starting with // are comments

CONCEPT: Curly Braces

• The inside of the two { } blocks are the definition of what the functions do.

CONCEPT: Compilation

• Turning your human readable text into machine readable binary code.

CONCEPT: Upload

• Pushing your binary to the Arduino.

Do it!

• Compile and upload the program above. What outputs do you observe?
• Add your name in the top-file multiline comment
• Add an empty function named 'hello'. Add a comment on what you think this function should do

Your First Output: PRINTLN

void setup() {
  Serial.begin(9600);
  Serial.println(F("My name is ..."));
}

void loop() {
}

NOTE: Semi-colons ";"

• Every instruction line (calls to functions, definition of variables) end up with a semi-colon (;)

Do it!

• Modify the string to add your own name
• Add a print out of a short description of yourself

Your First Subroutine

void setup() {
  Serial.begin(9600);
  output_name();
}

void loop() {
}


void output_name() {
  Serial.println(F("My name is ..."));
}

Do it!

• Add a second function called output_age and call it from loop
• Do two calls to output_name() and one call to output_age()
  • What do you observe?

• Move output_name() to inside output_age()
  • Is the behavior the same?

• Move the function calls to loop()
  • What is the difference in the behavior?

Your First Variable

void setup() {
  Serial.begin(9600);
  int age = 21;
  Serial.print(F("My age is "));
  Serial.println(age);
}

void loop() {
}

Do it!

• Modify the age variable to put your own age

Your First Condition: IF THEN

void setup() {
  Serial.begin(9600);
  int age = 21;
  Serial.print(F("My age is "));
  Serial.println(age);
  if(age < 22) {
    Serial.println(F("I'm young!"));
  }
  if(age > 22) {
    Serial.println(F("I'm old!"));
  }
}

void loop() {
}

Do it!

• The program given above has a bug. What is it?
• Change age to your age.
  • Change the conditions to always print "I'm young!"
  • Change the conditions to always print "I'm old!"
  • Change the conditions to always print both "I'm young!" and "I'm old!"

Your First Else Condition: IF THEN ELSE

void setup() {
  Serial.begin(9600);
  int age = 21;
  Serial.print(F("My age is "));
  Serial.println(age);
  if(age < 22) {
    Serial.println(F("I'm young!"));
  } else {
    Serial.println(F("I'm old!"));
  }
}

void loop() {
}

Do it!

• Swap the "I'm young!" string with the "I'm old!" string.
  • How do you need to change the condition so it's still valid?

Your First Interactive Input Program

void setup() {
  Serial.begin(9600);
  int input = Serial.read();
  Serial.println(input);
}

void loop() {
}

Do it!

• Move the code (except "Serial.begin(9600);" to loop()
  • What happens?
• Change Serial.println to Serial.print
  • What is the difference in the output? Why do we use Serial.println instead of Serial.print?

Your First Interactive (Input/Output) Program

void setup() {
  Serial.begin(9600);
}

void loop() {
  int input = Serial.read();
  if(input == 'h') {
    Serial.println(F("Hello!"));
  }
}

Do it!

• Add your own interactions when pressing other keys of your choice
• Move all your code except for "Serial.begin(9600);" to the loop() function
  • What is the difference in the behavior?

---

Debugging Compile Errors

These exercises help you recognize and fix compile errors. Find the error and fix it.

No Matching Function

void setup() {
  Serial.begin();
}

void loop() {
  Serial.println(F("My name is ..."));
}

Undefined Reference

/*
 * hello
void setup() {
  Serial.begin(9600);
}

void loop() {
  Serial.println(F("This program also does not compile"));
}
*/

Error: Expected ',' or ';' before '}' Token

void setup() {
}

void loop() {
 int i = 1
}

Does Not Declare Parameters

void setup() {
 int i = 1;
 int j = 2;
}

void loop() {
}

void my_function {
}

Missing terminating character

void setup() {
}

void loop() {
  Serial.println(F("My example program));
}

void my_function() {
}

See Also

• Introduction to programming using Arduino part 2 - More examples
• Arduino
• Introduction to Arduino
• Idiots Guide to Arduino
• Bonus reading: Von Neumann architecture