Initial Commit

main.c

@@ -0,0 +1,52 @@
+#include <avr/io.h>
+#include <avr/interrupt.h>
+
+#define ShiftRegister DDRD
+#define ShiftPort PORTD
+#define data (1<<PD5)
+#define latch (1<<PD6)
+#define clock (1<<PD7)
+
+unsigned char statusBit = 1;
+unsigned char slowdown = 0;
+
+int main(void)
+{
+  //Setup IO
+  ShiftRegister |= (data | latch | clock);	//Set outputs
+  ShiftPort &= ~(data | latch | clock);	//Set pins low
+
+  //Setup Timer
+  cli();		//disable all interrupts
+  TCCR0A |= (1<<WGM01);	//Use CTC mode
+  TCCR0B |= (1<<CS02) | (1<<CS00);//Start timer with 1024 prescaler
+  TIMSK0 |= (1<<OCIE0A);	//Enable the compare A interrupt
+  OCR0A = 0xFF;		//Set to compare to TOP
+  sei();		//enable all interrupts
+
+  while(1)
+  {
+    //Loop Forever
+  }
+}
+
+ISR(TIMER0_COMPA_vect){
+  if (++slowdown > 8){
+    //Set data pin
+    if (statusBit) ShiftPort |= data;
+    else ShiftPort &= ~data;
+
+
+    //Toggle clock pin
+    ShiftPort |= clock;
+    ShiftPort &= ~clock;
+    //latch
+    ShiftPort |= latch;
+    ShiftPort &= ~latch;
+
+    //prewind for next interrupt
+    statusBit ^= 1;
+    slowdown = 0;
+  }
+
+}