#include "sam.h"
 
#include <stdint.h>
 
int main(void)
{
	int u = 0;
	/* Initialize the SAM system */
	SystemInit();
 
	uint16_t last_time, now;
	last_time = now = 0;
 
	// LED pin, PA15, output
	PORT->Group[0].DIRSET.reg  = PORT_PA15;
 
	// Button pin, PA28, enable input driver and pull-up
	PORT->Group[0].PINCFG[28].bit.INEN = 1;
	PORT->Group[0].PINCFG[28].bit.PULLEN = 1;
	PORT->Group[0].OUTSET.reg = PORT_PA28;
 
	// Enable the external 32k oscillator. Enable the 32khz and the 1khz ouput from the oscillator.
	OSC32KCTRL->XOSC32K.reg = OSC32KCTRL_XOSC32K_ENABLE | OSC32KCTRL_XOSC32K_XTALEN | OSC32KCTRL_XOSC32K_EN32K | OSC32KCTRL_XOSC32K_STARTUP(3);
	while(!OSC32KCTRL->STATUS.bit.XOSC32KRDY); // Wait for oscillator to stabilize
 
	// Setup Generic Clock Generator 6 to be sourced from the external 32k crystal oscillator
	GCLK->GENCTRL[6].reg = GCLK_GENCTRL_DIV(1) | GCLK_GENCTRL_OE | GCLK_GENCTRL_GENEN | GCLK_GENCTRL_SRC(GCLK_GENCTRL_SRC_XOSC32K_Val);
	while(!GCLK->SYNCBUSY.bit.GENCTRL6); // Wait for synchronization to complete
 
	// Set PB12 as output from Generic Clock Generator 6
	PORT->Group[1].PMUX[6].bit.PMUXE = 7; // PORT->Group[1].PMUX[6] contains MUX settings for PB12 and PB13. Peripheral H selected (7)
	PORT->Group[1].PINCFG[12].bit.PMUXEN = 1; // Set PB12 to follow MUX setting
 
 
	// Setup Peripheral Channel for the TC1 timer to be sourced from Generator 6
	GCLK->PCHCTRL[TC1_GCLK_ID].reg = GCLK_PCHCTRL_CHEN | GCLK_PCHCTRL_GEN(GCLK_PCHCTRL_GEN_GCLK6_Val);
 
	// Enable Synchronous bus clock for TC1
	MCLK->APBCMASK.bit.TC1_ = 1;
 
	// Setup TC1 as a 16-bit counter. Enable the counter. Set the prescaler to 256.
	TC1->COUNT16.CTRLA.reg = TC_CTRLA_MODE(TC_CTRLA_MODE_COUNT16_Val) | TC_CTRLA_ENABLE | TC_CTRLA_PRESCALER(TC_CTRLA_PRESCALER_DIV256_Val);
	while(TC0->COUNT32.SYNCBUSY.bit.ENABLE); // Wait for synchronisazion to complete
 
	while (1) 
	{
		// Request synchronisazion of the counter register
		TC1->COUNT16.CTRLBSET.reg = TC_CTRLBSET_CMD(TC_CTRLBSET_CMD_READSYNC_Val);
		while(TC1->COUNT16.SYNCBUSY.bit.CTRLB); // Wait for command to synchronisaze
		while(TC1->COUNT16.SYNCBUSY.bit.COUNT); // Wait for counter register to synchronize
		// Read counter register
		now = TC1->COUNT16.COUNT.reg;
 
		// Simple blinking
		if((uint16_t)(now-last_time) >= 64)
		{
			PORT->Group[0].OUTTGL.reg = PORT_PA15; // Toggle output
			last_time = now;
		}
		// Reset timing if user button is held
		if(!(PORT->Group[0].IN.reg & PORT_PA28))
		{
			last_time = now;
		}
	}
}