added prescaler for 16 bit pwm in LPC1347 target
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targets/hal/TARGET_Freescale/TARGET_KSDK2_MCUS/api/lp_ticker.c
- Committer:
- <>
- Date:
- 2016-09-02
- Revision:
- 144:ef7eb2e8f9f7
File content as of revision 144:ef7eb2e8f9f7:
/* mbed Microcontroller Library * Copyright (c) 2016 ARM Limited * * Licensed under the Apache License, Version 2.0 (the "License"); * you may not use this file except in compliance with the License. * You may obtain a copy of the License at * * http://www.apache.org/licenses/LICENSE-2.0 * * Unless required by applicable law or agreed to in writing, software * distributed under the License is distributed on an "AS IS" BASIS, * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. * See the License for the specific language governing permissions and * limitations under the License. */ #if DEVICE_LOWPOWERTIMER #include "lp_ticker_api.h" #include "fsl_rtc.h" #include "fsl_lptmr.h" #include "cmsis.h" #include "rtc_api.h" #define MAX_SEC_BITS (12) #define MAX_SEC_MASK ((1 << MAX_SEC_BITS) - 1) #define SEC_IN_USEC (1000000) #define OSC32K_CLK_HZ (32768) #define MAX_LPTMR_SLEEP ((1 << 16) - 1) static bool lp_ticker_inited = false; static int lptmr_schedule = 0; static void rtc_isr(void) { 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(); } } static void lptmr_isr(void) { LPTMR_ClearStatusFlags(LPTMR0, kLPTMR_TimerCompareFlag); LPTMR_StopTimer(LPTMR0); lp_ticker_irq_handler(); } /** 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); } 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); } /** Read the current counter * * @return The current timer's counter value in microseconds */ uint32_t lp_ticker_read(void) { uint32_t sec, pre; if (!lp_ticker_inited) { lp_ticker_init(); } sec = RTC->TSR; /* 32b: Seconds */ pre = RTC->TPR; /* 16b: Increments every 32.768kHz clock cycle (30us) */ /* Final value: 11b (4095) for sec and 21b for usec (pre can reach 1,000,000us which is close to 1<<20) */ uint32_t ret = (((sec & MAX_SEC_MASK) * SEC_IN_USEC) + (((uint64_t)pre * SEC_IN_USEC) / OSC32K_CLK_HZ)); return ret; } /** 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); } } /** Disable low power ticker interrupt * */ void lp_ticker_disable_interrupt(void) { LPTMR_DisableInterrupts(LPTMR0, kLPTMR_TimerInterruptEnable); RTC_DisableInterrupts(RTC, kRTC_AlarmInterruptEnable); } /** Clear the low power ticker interrupt * */ void lp_ticker_clear_interrupt(void) { RTC->TAR = 0; /* Write clears the IRQ flag */ LPTMR_ClearStatusFlags(LPTMR0, kLPTMR_TimerCompareFlag); } #endif /* DEVICE_LOWPOWERTIMER */