Timer.cpp

/* 
 * File:   Timer.cpp
 * Author: Blake Tacklind
 *
 * Created on August 31, 2015, 5:55 PM
 */

#include "Timer.h"

void Timer::init() {
	/*
	 * COM3A1  COM3A0  COM3B1  COM3B0  COM3C1  COM3C0    WGM31   WGM30
	 * 0       0       0       0       0       0         0       0
	 * Normal port   | Normal port     | Normal port    | CTC Mode
	 * operations    | operations      | operations     |
	 */
	TCCR3A = 0b00000000;

	/*
	 * Setup for CTC mode but not yet running
	 * ICNC3    ICES3   ~~~~~    WGM33    WGM32    CS32    CS31   CS30
	 * 0        0                0        1        0       0      0
	 * Noise   |Edge            | CTC OCR3A       | Clock
	 * Canceler|Select          | Mode            | Initially stopped
	 */
	// We'll using this const in a second
	u1 constexpr B = 0b00001000;
	TCCR3B = B;

	/*
	 * Disable all interrupts
	 * ~~~~~   ~~~~~   ICIE3   ~~~~~   OCIE3C  OCIE3B  OCIE0A  TOIE0 
	 *                 0               0       0       0       0
	 *                Input Capture   | Disabled Interrupts
	 *               Interrupt Enable |
	 */
	TIMSK3 = 0b00000000;

	// Start the timer at 0 just to be nice
	TCNT3 = 0;

	// Setup the correct timer TOP value
	OCR3A = TOP;

	// Clear all timer interrupt flags
	TIFR3 = 0xff;

	// Start the timer
	TCCR3B = B | CLKprescaler;

}

u2 Timer::getSince(const u2 time) {
	const u2 t = getCurTime();
	if (t > time)
		return t - time;
	
	return CountsPerClear + t - time;
}