#include "delay.h"

static volatile uint32_t usTicks = 0;
vu32 sysTickUptime;

void cycleCounterInit(void)
{
    RCC_ClocksTypeDef clocks;
    RCC_GetClocksFreq(&clocks);
    usTicks = clocks.SYSCLK_Frequency / 1000000;
    SysTick_Config(clocks.HCLK_Frequency / 1000);  //SysTick开启系统tick定时器并初始化其中断，1m
}

uint32_t Micros(void)//得到总的时间。
{
	register uint32_t ms, cycle_cnt, usTicks_t;
  
	do {
      ms = sysTickUptime;
      cycle_cnt = SysTick->VAL;
  }while (ms != sysTickUptime);
  usTicks_t = usTicks;
	
  return (ms * 1000) + (usTicks_t * 1000 - cycle_cnt) / usTicks_t;
}

void delay_us(u32 nus)//微秒延时 
{
		uint32_t t0 = Micros();
		while(Micros() - t0 < nus);
}

void delay_ms(u16 nms)//毫秒延时
{
		uint32_t t0 = Micros();
		while(Micros() - t0 < nms * 1000);
}

uint32_t millis(void)// Return system uptime in milliseconds (rollover in 49 days)
{
    return sysTickUptime;
}