Lab 18 - Using Timer Interrupts

CLASSWORK:
Blinking LED with Timer Interrupts:
//Using Timer Interrupts with the Arduino
#include <TimerOne.h>
const int LED=13;

void setup() 
{
  pinMode(LED, OUTPUT);
  Timer1.initialize(1000000); //Set a timer of length 1000000
                              //microseconds (1 second)
  Timer1.attachInterrupt(blinky); //Runs "blinky" on each 
                                  //time interrupt
}
void loop() 
{
  // put your main code here, to run repeatedly:
}
//Timer interrupt function
void blinky()
{
  digitalWrite(LED, !digitalRead(LED)); //Toggle LED State
}

HOMEWORK:
Basic Speaker with Hardware and Timer Interrupts:
//Use Hardware and Timer Interrupts for Fun with Sound
//Include the TimerOne library
#include <TimerOne.h>
//Button pins
const int BUTTON_INT =0;
const int SPEAKER    =12;
//Music keys
#define NOTE_C 65
#define NOTE_D 73
#define NOTE_E 82
#define NOTE_F 87
#define NOTE_G 98
#define NOTE_A 110
#define NOTE_B 123
//Volatile variables can change inside interrupts
volatile int key = NOTE_C;
volatile int octave_multiplier = 1;

void setup() 
{
  //Set up Serial
  Serial.begin(9600);
  
  pinMode(SPEAKER, OUTPUT);
  //The pin is inverted, so we want to look at the rising edge
  attachInterrupt(BUTTON_INT, changeKey, RISING);

  //Set up timer interrupt
  Timer1.initialize(500000); //Set a timer of length .5 seconds
  Timer1.attachInterrupt(changePitch); //Runs "blinky" on each 
                                  //time interrupt
}
void changeKey()
{
  octave_multiplier = 1;
  if (key == NOTE_C)
    key = NOTE_D;
  else if (key == NOTE_D)
    key = NOTE_E;
  else if (key == NOTE_E)
    key = NOTE_F;
  else if (key == NOTE_F)
    key = NOTE_G;
  else if (key == NOTE_G)
    key = NOTE_A; 
  else if (key == NOTE_A)
    key = NOTE_B;
  else if (key == NOTE_B)
    key = NOTE_C;   
}
//Timer interrupt function
void changePitch()
{
  octave_multiplier = octave_multiplier * 2;
  if (octave_multiplier > 16) octave_multiplier = 1;
  tone(SPEAKER, key*octave_multiplier);
}

void loop() 
{
  Serial.print("Key: ");
  Serial.print(key);
  Serial.print(" Multiplier ");
  Serial.print(octave_multiplier);
  Serial.print(" Frequency ");
  Serial.println(key*octave_multiplier);
  delay(100);
}