mbed-os/targets/TARGET_Silicon_Labs/TARGET_EFM32/lp_ticker.c

/***************************************************************************//**
 * @file lp_ticker.c
 *******************************************************************************
 * @section License
 * <b>(C) Copyright 2015 Silicon Labs, http://www.silabs.com</b>
 *******************************************************************************
 *
 * SPDX-License-Identifier: Apache-2.0
 *
 * 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.
 *
 ******************************************************************************/

#include "device.h"
#include "clocking.h"
#if DEVICE_LOWPOWERTIMER

#include "rtc_api.h"
#include "rtc_api_HAL.h"
#include "lp_ticker_api.h"

#include "mbed_critical.h"
#if (defined RTCC_COUNT) && (RTCC_COUNT > 0)
#include "em_rtcc.h"
#endif

static int rtc_reserved = 0;

void lp_ticker_init()
{
    if(!rtc_reserved) {
        core_util_critical_section_enter();
        rtc_init_real(RTC_INIT_LPTIMER);
        rtc_set_comp0_handler((uint32_t)lp_ticker_irq_handler);
        rtc_reserved = 1;
        core_util_critical_section_exit();
    }
}

void lp_ticker_free()
{
    if(rtc_reserved) {
        core_util_critical_section_enter();
        rtc_free_real(RTC_INIT_LPTIMER);
        rtc_reserved = 0;
        core_util_critical_section_exit();
    }
}

#ifndef RTCC_COUNT

/* RTC API */

void lp_ticker_set_interrupt(timestamp_t timestamp)
{
    uint64_t timestamp_ticks;
    uint64_t current_ticks = RTC_CounterGet();
    timestamp_t current_time = ((uint64_t)(current_ticks * 1000000) / (LOW_ENERGY_CLOCK_FREQUENCY / RTC_CLOCKDIV_INT));

    /* Initialize RTC */
    lp_ticker_init();

    /* calculate offset value */
    timestamp_t offset = timestamp - current_time;
    if(offset > 0xEFFFFFFF) offset = 100;

    /* map offset to RTC value */
    // ticks = offset * RTC frequency div 1000000
    timestamp_ticks = ((uint64_t)offset * (LOW_ENERGY_CLOCK_FREQUENCY / RTC_CLOCKDIV_INT)) / 1000000;
    timestamp_ticks += current_ticks;

    /* RTC has 24 bit resolution */
    timestamp_ticks &= 0xFFFFFF;

    /* check for RTC limitation */
    if((timestamp_ticks - RTC_CounterGet()) >= 0x800000) timestamp_ticks = RTC_CounterGet() + 2;

    /* Set callback */
    RTC_FreezeEnable(true);
    RTC_CompareSet(0, (uint32_t)timestamp_ticks);
    RTC_IntEnable(RTC_IF_COMP0);
    RTC_FreezeEnable(false);
}

inline void lp_ticker_disable_interrupt()
{
    RTC_IntDisable(RTC_IF_COMP0);
    lp_ticker_free();
}

inline void lp_ticker_clear_interrupt()
{
    RTC_IntClear(RTC_IF_COMP0);
}

timestamp_t lp_ticker_read()
{
    lp_ticker_init();
    
    uint64_t ticks_temp;
    uint64_t ticks = RTC_CounterGet();

    /* ticks = counter tick value
     * timestamp = value in microseconds
     * timestamp = ticks * 1.000.000 / RTC frequency
     */

    ticks_temp = (ticks * 1000000) / (LOW_ENERGY_CLOCK_FREQUENCY / RTC_CLOCKDIV_INT);
    return (timestamp_t) (ticks_temp & 0xFFFFFFFF);
}

#else

/* RTCC API */

void lp_ticker_set_interrupt(timestamp_t timestamp)
{
    uint64_t timestamp_ticks;
    uint64_t current_ticks = RTCC_CounterGet();
    timestamp_t current_time = ((uint64_t)(current_ticks * 1000000) / (LOW_ENERGY_CLOCK_FREQUENCY / RTC_CLOCKDIV_INT));

    /* Initialize RTC */
    lp_ticker_init();

    /* calculate offset value */
    timestamp_t offset = timestamp - current_time;
    if(offset > 0xEFFFFFFF) offset = 100;

    /* map offset to RTC value */
    // ticks = offset * RTC frequency div 1000000
    timestamp_ticks = ((uint64_t)offset * (LOW_ENERGY_CLOCK_FREQUENCY / RTC_CLOCKDIV_INT)) / 1000000;
    // checking the rounding. If timeout is wanted between RTCC ticks, irq should be configured to
    // trigger in the latter RTCC-tick. Otherwise ticker-api fails to send timer event to its client
    if(((timestamp_ticks * 1000000) / (LOW_ENERGY_CLOCK_FREQUENCY / RTC_CLOCKDIV_INT)) < offset){
        timestamp_ticks++;
    }

    timestamp_ticks += current_ticks;

    /* RTCC has 32 bit resolution */
    timestamp_ticks &= 0xFFFFFFFF;

    /* check for RTCC limitation */
    if((timestamp_ticks - RTCC_CounterGet()) >= 0x80000000) timestamp_ticks = RTCC_CounterGet() + 2;

    /* init channel */
    RTCC_CCChConf_TypeDef ccchConf = RTCC_CH_INIT_COMPARE_DEFAULT;
    RTCC_ChannelInit(0,&ccchConf);
    /* Set callback */
    RTCC_ChannelCCVSet(0, (uint32_t)timestamp_ticks);
    RTCC_IntEnable(RTCC_IF_CC0);
}

inline void lp_ticker_disable_interrupt()
{
    RTCC_IntDisable(RTCC_IF_CC0);
    lp_ticker_free();
}

inline void lp_ticker_clear_interrupt()
{
    RTCC_IntClear(RTCC_IF_CC0);
}

timestamp_t lp_ticker_read()
{
    lp_ticker_init();
    
    uint64_t ticks_temp;
    uint64_t ticks = RTCC_CounterGet();

    /* ticks = counter tick value
     * timestamp = value in microseconds
     * timestamp = ticks * 1.000.000 / RTC frequency
     */

    ticks_temp = (ticks * 1000000) / (LOW_ENERGY_CLOCK_FREQUENCY / RTC_CLOCKDIV_INT);
    return (timestamp_t) (ticks_temp & 0xFFFFFFFF);
}

#endif /* RTCC */

#endif