Call from setup...
void analogWriteSAH_Init( void )
{
// Stop the timer while we muck with it
TCCR1B = (0 << ICNC1) | (0 << ICES1) | (0 << WGM13) | (0 << WGM12) | (0 << CS12) | (0 << CS11) | (0 << CS10);
// Set the timer to mode 14...
//
// Mode WGM13 WGM12 WGM11 WGM10 Timer/Counter Mode of Operation TOP Update of OCR1x at TOV1 Flag Set on
// CTC1 PWM11 PWM10
// ---- ----- ----- ----- ----- ------------------------------- ---- ----------------------- -----------
// 14 1 1 1 0 Fast PWM ICR1 BOTTOM TOP
// Set output on Channel A and B to...
//
// COM1z1 COM1z0 Description
// ------ ------ -----------------------------------------------------------
// 1 0 Clear OC1A/OC1B on Compare Match (Set output to low level).
TCCR1A =
(1 << COM1A1) | (0 << COM1A0) | // COM1A1, COM1A0 = 1, 0
(1 << COM1B1) | (0 << COM1B0) |
(1 << WGM11) | (0 << WGM10); // WGM11, WGM10 = 1, 0
// Set TOP to...
//
// fclk_I/O = 16000000
// N = 1
// TOP = 799
//
// fOCnxPWM = fclk_I/O / (N * (1 + TOP))
// fOCnxPWM = 16000000 / (1 * (1 + 799))
// fOCnxPWM = 16000000 / 800
// fOCnxPWM = 20000
ICR1 = 799;
// Ensure the first slope is complete
TCNT1 = 0;
// Ensure Channel A and B start at zero / off
OCR1A = 0;
OCR1B = 0;
// We don't need no stinkin interrupts
TIMSK1 = (0 << ICIE1) | (0 << OCIE1B) | (0 << OCIE1A) | (0 << TOIE1);
// Ensure the Channel A and B pins are configured for output
DDRB |= (1 << DDB1);
DDRB |= (1 << DDB2);
// Start the timer...
//
// CS12 CS11 CS10 Description
// ---- ---- ---- ------------------------
// 0 0 1 clkI/O/1 (No prescaling)
TCCR1B =
(0 << ICNC1) | (0 << ICES1) |
(1 << WGM13) | (1 << WGM12) | // WGM13, WGM12 = 1, 1
(0 << CS12) | (0 << CS11) | (1 << CS10);
}