// 通过直接计算校准RTC时钟(使用0.01ms周期的systick测量再修正RTC预分频系数)。
void RTC_Calibrate(void)
{
unsigned int systick_sta;
unsigned int rtctick_lmt;
unsigned int prescaler = 0;
// 在使用systick测量RTC tick的周期长度之前，初始化systick
NVIC_SetPriority(SysTick_IRQn, 0);
SysTick_Init();
// 开始rtcalarm计数并使能rtcalarm中断
SysTick_Enable();
// 先设置默认的RTC预分频系数(rtc tike = ~1ms)
RTC_SetPrescaler(DEF_RTC_PRESCALER);
/* Enable RTC Clock */
RCC_RTCCLKCmd(ENABLE);
/* Wait for RTC registers synchronization */
RTC_WaitForSynchro();
/* Wait until last write operation on RTC registers has finished */
RTC_WaitForLastTask();
// 测量RTC单周期长度持续~1秒
rtctick_lmt = systick+1000/SYSTICK_PERIOD;
// 记录测量前的systick值
systick_sta = systick;
// 测量1000个周期的rtc tick(~1s)
while(systick < rtctick_lmt);
prescaler = (DEF_RTC_PRESCALER * 1000)/((systick-systick_sta)/100);
// printf("prescaler = %d.\r\n", prescaler);
// 重新设置RTC预分频系数
RTC_SetPrescaler(prescaler);
/* Enable RTC Clock */
RCC_RTCCLKCmd(ENABLE);
/* Wait for RTC registers synchronization */
RTC_WaitForSynchro();
/* Wait until last write operation on RTC registers has finished */
RTC_WaitForLastTask();
// 校准完RTC时钟后，停止rtcalarm计数并禁止rtcalarm中断
SysTick_Disable();
// printf("RTC Clock calibrated.\r\n");
}
// ************** SysTick_Init ****************************
// - Initializes the Systick timer
// ********************************************************
// Input: none
// Output: none
// ********************************************************
void SysTick_Init(){
// disable systick while it is being initialized
SysTick_Disable();
// set period to maximum value
SysTick_SetPeriod(0xFFFFFF);
// reset counter value
SysTick_Reset();
// set interrupt priority
SysTick_SetInterruptPriority();
// enable systick
SysTick_Enable();
}
/**************************************************************************//**
* @brief Main function
*****************************************************************************/
int main(void)
{
WDOG_Init_TypeDef wInit = WDOG_INIT_DEFAULT;
int i;
/* Chip revision alignment and errata fixes */
CHIP_Init();
/* If first word of user data page is non-zero, enable eA Profiler trace */
BSP_TraceProfilerSetup();
/* Watchdog setup - Use defaults, excepts for these :*/
wInit.em2Run = true;
wInit.em3Run = true;
wInit.perSel = wdogPeriod_4k; /* 4k 1kHz periods should give ~4 seconds in EM3 */
/* Do the demo forever. */
/* EM0 - 1 sec HFXO */
CMU_ClockSelectSet(cmuClock_HF, cmuSelect_HFXO);
/* Setup SysTick Timer for 1 msec interrupts */
if (SysTick_Config(CMU_ClockFreqGet(cmuClock_CORE) / 1000))
{
while (1) ;
}
Delay(1000);
/* EM0 - 1 sec HFRCO */
CMU_ClockSelectSet(cmuClock_HF, cmuSelect_HFRCO);
/* Setup SysTick Timer for 1 msec interrupts */
if (SysTick_Config(CMU_ClockFreqGet(cmuClock_CORE) / 1000))
{
while (1) ;
}
Delay(1000);
/* Turn off systick */
SysTick_Disable();
/* EM1 - 1 sec */
RTCDRV_Trigger(1000, NULL);
EMU_EnterEM1();
/* EM2 - 1 sec */
RTCDRV_Trigger(1000, NULL);
EMU_EnterEM2(true);
/* EM1 - 1 sec */
RTCDRV_Trigger(1000, NULL);
EMU_EnterEM1();
/* EM2 - 1 sec */
RTCDRV_Trigger(1000, NULL);
EMU_EnterEM2(true);
/* Up and down from EM2 each 10 msec */
for (i=0; i < 10; i++)
{
RTCDRV_Trigger(10, NULL);
EMU_EnterEM2(true);
RTCDRV_Delay(10, false);
}
/* EM2 - 1 sec */
RTCDRV_Trigger(1000, NULL);
EMU_EnterEM2(true);
/* Up and down from EM2 each 2 msec */
for (i=0; i < 10; i++)
{
RTCDRV_Trigger(2, NULL);
EMU_EnterEM2(true);
}
/* EM2 - 1 sec */
RTCDRV_Trigger(1000, NULL);
EMU_EnterEM2(true);
/* Up and down from EM2 each msec */
for (i=0; i < 10; i++)
{
RTCDRV_Trigger(1, NULL);
EMU_EnterEM2(true);
}
/* EM2 - 1 sec */
RTCDRV_Trigger(1000, NULL);
EMU_EnterEM2(true);
/* Start watchdog */
WDOG_Init(&wInit);
/* Enter EM3 - Watchdog will reset chip (and confuse debuggers) */
EMU_EnterEM3(true);
/* We will never reach this point */
return 0;
}
