/** 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); } }