#include "systick.h"

systick_t *get_systick() {
	return (systick_t *) 0xE000E010;
}

// This function is to Initialize SysTick registers
void init_systick()
{
	// Use the SysTick global structure pointer to do the following in this
	// exact order with separate lines for each step:
	//
	// Disable SysTick by clearing the CTRL (CSR) register.
	// Set the LOAD (RVR) to 8 million to give us a 100 milliseconds timer.
	// Set the clock source bit in the CTRL (CSR) to the internal clock.
	// Set the enable bit in the CTRL (CSR) to start the timer.
	systick_t *s = get_systick();

	s->CSR &= ~1;
	s->CSR |= 1<<2;
	s->CSR |= 1<<1; // enable interrupt
	s->RVR = 78124; // 100 ms
	s->CSR |= 1;
}

// This fuction is to create delay using SysTick timer counter
void delay_systick()
{
	// Using the SysTick global structure pointer do the following:
	// Create a for loop that loops 10 times
	// Inside that for loop check the COUNTFLAG bit in the CTRL (CSR)
	// register in a loop. When that bit is set exit this inner loop
	// to do another pass in the outer loop of 10.
	systick_t *s = get_systick();

	for (int i = 0; i < 10; i++) {
		while (~s->CSR & (1<<16))
			;
	}
}

int check_systick() {
	static int i = 0;

	systick_t *s = get_systick();
	if (!(~s->CSR & (1<<16))) {
		i++;
	}

	if (i >= 10) {
		i = 0;
		return 1;
	} else {
		return 0;
	}
}