Timer 1 ISR and Registers

Set Timer 1 Output Compare Match Interrupt with frequency 1Hz. Setup with direct access to registers.

diff --git a/Timer_ISR/Timer_ISR.ino b/Timer_ISR/Timer_ISR.ino
new file mode 100644 (file)
index 0000000..1517d2e
--- /dev/null
+++ b/Timer_ISR/Timer_ISR.ino
@@ -0,0 +1,38 @@
+boolean toggle1 = 0;
+
+void setup() {
+  pinMode(13, OUTPUT);
+  noInterrupts(); //cli(); // Stop reception of interrupts
+
+  // Set Timer 1 Control registers and counter to 0
+  TCCR1A = 0;
+  TCCR1B = 0;
+  TCNT1  = 0;
+
+  // Set compare match value = Fclk_io / (Fout * Prescaler) - 1
+  OCR1A = 15624; // = (16MHz) / (1 * 1024) - 1
+  TIMSK1 |= (1 << OCIE1A); // Enable compare match interrupt
+
+  // Set Timer 1 Mode of operation and clock prescalers
+  TCCR1B |= (1 << WGM12); // Mode 4
+  TCCR1B |= (1 << CS12) | (1 << CS10); // Set prescaler to 1024 (=> enable the clock)
+  
+  
+  interrupts(); //sei();
+}
+
+void loop() {
+  // put your main code here, to run repeatedly:
+}
+
+ISR(TIMER1_COMPA_vect){//timer1 interrupt 1Hz toggles pin 13 (LED)
+//generates pulse wave of frequency 1Hz/2 = 0.5kHz (takes two cycles for full wave- toggle high then toggle low)
+  if (toggle1){
+    digitalWrite(13,HIGH);
+    toggle1 = 0;
+  }
+  else{
+    digitalWrite(13,LOW);
+    toggle1 = 1;
+  }
+}