added prescaler for 16 bit pwm in LPC1347 target
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Diff: targets/hal/TARGET_Freescale/TARGET_KSDK2_MCUS/api/lp_ticker.c
- Revision:
- 144:ef7eb2e8f9f7
diff -r 423e1876dc07 -r ef7eb2e8f9f7 targets/hal/TARGET_Freescale/TARGET_KSDK2_MCUS/api/lp_ticker.c --- /dev/null Thu Jan 01 00:00:00 1970 +0000 +++ b/targets/hal/TARGET_Freescale/TARGET_KSDK2_MCUS/api/lp_ticker.c Fri Sep 02 15:07:44 2016 +0100 @@ -0,0 +1,172 @@ +/* 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 */