Set timer2 for DCC's 58us cycle period.

src/timer2_dcc_gen/timer2_dcc_gen.pde

@@ -18,37 +18,58 @@ unsigned int mycount = 0;
 
 void setup() {
 
-  // Enable Timer2 
-  OCR2A = timer2_target;
-  bitSet(TCCR2B, CS22);
-  bitSet(TCCR2B, CS21);
-  bitSet(TCCR2B, CS20);
+  // Setup Timer2 
+  configure_for_dcc_timing();
 
   pinMode(13,OUTPUT);
   pinMode(9,OUTPUT);
   pinMode(12,OUTPUT);
-
   digitalWrite(9,LOW);
-  // Enable Timer2 interrupt
-  bitSet(TIMSK2, OCIE2A); 
-  sei();  
+
+  sei();  // Enable interrupts
 }
 
+
 ISR( TIMER2_COMPA_vect ){
   mycount += 1;
 
-  if( mycount == 2 ) {
+  if( (mycount & 1 ) == HIGH ) {
     LED_OFF();
     LED1_ON();
-  } else if (mycount == 4    ) {
+  } else {
     LED_ON();
     LED1_OFF();
-    mycount = 0;
   }  
-  TCNT2 = 0;
+
+  TCNT2 = 0; // Reset Timer2 counter to divide...
 
 };
 
+void configure_for_dcc_timing() {
+
+  /* DCC timing requires that the data toggles every 58us
+  for a '1'. So, we set up timer2 to fire an interrupt every
+  58us, and we'll change the output in the interrupt service 
+  routine.
+ 
+  Prescaler: set to divide-by-8 (B'010)
+  Compare target: 58us / ( 1 / ( 16MHz/8) ) = 116
+  */
+
+  byte timer2_target = 114; // remember off-by-one -> count starts at 0
+
+  // Set prescaler to div-by-8
+  bitClear(TCCR2B, CS22);
+  bitSet(TCCR2B, CS21);
+  bitClear(TCCR2B, CS20);
+
+  // Set counter target
+  OCR2A = timer2_target;
+
+  // Enable Timer2 interrupt
+  bitSet(TIMSK2, OCIE2A); 
+}
+
 
 void loop(){
 }