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// LEDs and switchs
const byte ledPin1 = 11;
const byte ledPin2 = 13;
const byte buttonPin1= 2;
const byte buttonPin2 = 7;
// Booleans for input states
volatile bool D2_state = LOW;
volatile bool D7_state = LOW;
void setup() {
// Set LEDs as output
pinMode(ledPin1, OUTPUT) ;
pinMode(ledPin2, OUTPUT) ;
// Set Switches as input with pullup
pinMode(buttonPin1, INPUT_PULLUP) ;
pinMode(buttonPin2, INPUT_PULLUP) ;
// Enable PCIE2 Bit3 = 1 (Port D)|
PCICR |= 800000100;
//Enable interrupt on Pin D2 & D7 - Select PCINT18 & PCINT23 (Pin D2 & D7)
PCMSK2 |= B10000100;
}
void loop(){
// No code in Loop
}
ISR (PCINT2_vect)
{
// Port D Interrupt occured
// Check if this was D2
if (digitalRead(buttonPin1) == LOW) {
//Pin D2 triggered the ISR on a Falling pulse
D2_state = !D2_state;
//Set LED 1 to state of D2 state boolean
digitalWrite(ledPin1, D2_state);
}
// Check if this was D7
if (digitalRead(buttonPin2) == LOW) {
//Pin D7 triggered the ISR on a Falling pulse
D7_state = !D7_state;
//Set LED 2 to state of D7_state boolean
digitalWrite(ledPin2, D7_state);
}
} |
Timer Interrupts
Do not use a timer that is used by another process.
Arduino Uno Timers
Replace x with 0,1, or 2 representing the timer #.
Code Sample
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//define the LED pin
#define ledPin 13
//Define timer compare match register value
int timer1_compare_match;
ISR(TIMER1_COMPA_vect){
//Interrupt Service Routine for Compare Mode
//Preload timer with compare match value
TCNT1 = timer_compare_match;
//Write opposite value to LED
digitalWrite(ledPin, digitalRead(ledPin) ^ 1);
}
void setup(){
//Set LED as output
pinMode(ledPin, OUTPUT);
//Disable all interrupts
noInterrupts();
//Initialize Timer1
TCCR1A = 0;
TCCR1B = 0;
//Set timerl_compare_match to the correct compare match register value
// 256 prescaler & 31246 compare match = 2Hz
timer_compare_match = 31249;
//Preload timer with compare match value
TCNT1 = timer1_compare_match;
// Preload timer with compare match value
TCNT1 = timer1_compare_match;
// Set prescaler to 256 - set CS12 bit in TCCR1B
TCCR1B = (1 < CS12) ;
// Enable timer interrupt for compare mode
TIMSK1 |= (1 < OCIE1A);
// Enable all interrupts
interrupts ();
}
void loop() {
//nothing
} |
Analyzing the Following Code
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