/** Initialize the low power ticker
*
*/
void lp_ticker_init(void)
{
lptmr_config_t lptmrConfig;
if (lp_ticker_inited) {
return;
}
lp_ticker_inited = true;
/* Setup low resolution clock - RTC */
if (!rtc_isenabled()) {
rtc_init();
RTC_DisableInterrupts(RTC, kRTC_AlarmInterruptEnable | kRTC_SecondsInterruptEnable);
RTC_StartTimer(RTC);
}
RTC->TAR = 0; /* Write clears the IRQ flag */
NVIC_ClearPendingIRQ(RTC_IRQn);
NVIC_SetVector(RTC_IRQn, (uint32_t)rtc_isr);
NVIC_EnableIRQ(RTC_IRQn);
/* Setup high resolution clock - LPTMR */
LPTMR_GetDefaultConfig(&lptmrConfig);
/* Use 32kHz drive */
CLOCK_SetXtal32Freq(OSC32K_CLK_HZ);
lptmrConfig.prescalerClockSource = kLPTMR_PrescalerClock_2;
LPTMR_Init(LPTMR0, &lptmrConfig);
LPTMR_EnableInterrupts(LPTMR0, kLPTMR_TimerInterruptEnable);
NVIC_ClearPendingIRQ(LPTMR0_IRQn);
NVIC_SetVector(LPTMR0_IRQn, (uint32_t)lptmr_isr);
EnableIRQ(LPTMR0_IRQn);
}
/*!
* @brief Main function
*/
int main(void)
{
uint32_t currentCounter = 0U;
lptmr_config_t lptmrConfig;
LED_INIT();
/* Board pin, clock, debug console init */
BOARD_InitPins();
BOARD_BootClockRUN();
BOARD_InitDebugConsole();
/* Configure LPTMR */
/*
* lptmrConfig.timerMode = kLPTMR_TimerModeTimeCounter;
* lptmrConfig.pinSelect = kLPTMR_PinSelectInput_0;
* lptmrConfig.pinPolarity = kLPTMR_PinPolarityActiveHigh;
* lptmrConfig.enableFreeRunning = false;
* lptmrConfig.bypassPrescaler = true;
* lptmrConfig.prescalerClockSource = kLPTMR_PrescalerClock_1;
* lptmrConfig.value = kLPTMR_Prescale_Glitch_0;
*/
LPTMR_GetDefaultConfig(&lptmrConfig);
/* Initialize the LPTMR */
LPTMR_Init(LPTMR0, &lptmrConfig);
/* Set timer period */
LPTMR_SetTimerPeriod(LPTMR0, USEC_TO_COUNT(1000000U, LPTMR_SOURCE_CLOCK));
/* Enable timer interrupt */
LPTMR_EnableInterrupts(LPTMR0, kLPTMR_TimerInterruptEnable);
/* Enable at the NVIC */
EnableIRQ(LPTMR0_IRQn);
PRINTF("Low Power Timer Example\r\n");
/* Start counting */
LPTMR_StartTimer(LPTMR0);
while (1)
{
if (currentCounter != lptmrCounter)
{
currentCounter = lptmrCounter;
PRINTF("LPTMR interrupt No.%d \r\n", currentCounter);
}
}
}
/** Set interrupt for specified timestamp
*
* @param timestamp The time in microseconds to be set
*/
void lp_ticker_set_interrupt(timestamp_t timestamp)
{
uint32_t now_us, delta_us, delta_ticks;
if (!lp_ticker_inited) {
lp_ticker_init();
}
lptmr_schedule = 0;
now_us = lp_ticker_read();
delta_us = timestamp > now_us ? timestamp - now_us : (uint32_t)((uint64_t)timestamp + 0xFFFFFFFF - now_us);
/* Checking if LPTRM can handle this sleep */
delta_ticks = USEC_TO_COUNT(delta_us, CLOCK_GetFreq(kCLOCK_Er32kClk));
if (delta_ticks > MAX_LPTMR_SLEEP) {
/* Using RTC if wait time is over 16b (2s @32kHz) */
uint32_t delta_sec;
delta_us += COUNT_TO_USEC(RTC->TPR, CLOCK_GetFreq(kCLOCK_Er32kClk)); /* Accounting for started second */
delta_sec = delta_us / SEC_IN_USEC;
delta_us -= delta_sec * SEC_IN_USEC;
RTC->TAR = RTC->TSR + delta_sec - 1;
RTC_EnableInterrupts(RTC, kRTC_AlarmInterruptEnable);
/* Set aditional, subsecond, sleep time */
if (delta_us) {
lptmr_schedule = USEC_TO_COUNT(delta_us, CLOCK_GetFreq(kCLOCK_Er32kClk));
}
} else {
/* Below RTC resolution using LPTMR */
LPTMR_SetTimerPeriod(LPTMR0, delta_ticks);
LPTMR_EnableInterrupts(LPTMR0, kLPTMR_TimerInterruptEnable);
LPTMR_StartTimer(LPTMR0);
}
}
static void rtc_isr(void)
{
uint32_t sr = RTC->SR;
if (sr & RTC_SR_TOF_MASK) {
// Reset RTC to 0 so it keeps counting
RTC_StopTimer(RTC);
RTC->TSR = 0;
RTC_StartTimer(RTC);
} else if (sr & RTC_SR_TAF_MASK) {
RTC_DisableInterrupts(RTC, kRTC_AlarmInterruptEnable);
RTC->TAR = 0; /* Write clears the IRQ flag */
/* Wait subsecond remainder if any */
if (lptmr_schedule) {
LPTMR_SetTimerPeriod(LPTMR0, lptmr_schedule);
LPTMR_EnableInterrupts(LPTMR0, kLPTMR_TimerInterruptEnable);
LPTMR_StartTimer(LPTMR0);
} else {
lp_ticker_irq_handler();
}
} else if (sr & RTC_SR_TIF_MASK) {
RTC_DisableInterrupts(RTC, kRTC_TimeOverflowInterruptEnable);
}
}
