/*
 * Program to build a stroboscoop to trim the speed of a record player. 
 * White led anode via 100 ohm to Vcc, kathode to drain of BS170, Gate of BS170 to PB2/OC1B
 * pulse frequency = 100Hz
 * pulse duty cycle = 25%
 */
#define LED_WHITE 10                            // PB2/OC1B
 
 void setup()
{
  pinMode(LED_WHITE,OUTPUT);
/*
 * init timer 1
 * - prescaler = /64 --> 16 MHz --> 250 kHz
 * - phase and frequency correct --> 125 kHz
 * - counts to 1250 for 100 Hz
 * - OCR1B set to 312 for 25% duty cycle
 * 
 * CS1x = 011                -- devide by 64
 * WGM1x = 1000              -- Phase and frequency correct PWM, counter endvalue in ICR1
 */
  TCCR1A = (1 << COM1A1) | (1 << COM1B1);      // WGM1x = xx00; COM1ax = 10; COM1bx = 10
  TCCR1B = (1 << CS10) | (1 << CS11) | (1 << WGM13);    // WGM1x = 10xx; CS1x = 011
  ICR1 = 1249;                                 // 1250 - 1
  OCR1B = 312;
  
  return;
}
/*
 * nothing to do here
 */
void loop()
{
  return;
}