LowerPower ticker implementation for LPC1768

lp_ticker.c

/*
 * Copyright (c) 2016 ARM Limited
 * 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 "cmsis.h"
#include "device.h"

#if DEVICE_LOWPOWERTIMER

#include "lp_ticker_api.h"
#include "sleep_api.h"
#include "objects.h"

static uint32_t lp_ticker_inited = 0;
static uint32_t lp_compare_value = 0xFFFFFFFFLu;
static volatile uint32_t overflows = 0;

#define LP_TIMER      ((LPC_RIT_TypeDef *)LPC_RIT_BASE)
#define LP_TIMER_IRQn RIT_IRQn

static void lptmr_isr(void);

static void lptmr_isr(void)
{
    LP_TIMER->RICOUNTER = 0;
    LP_TIMER->RICTRL |= 1;
    overflows++;
}

void lp_ticker_init(void)
{
    if (lp_ticker_inited) {
        return;
    }
    lp_ticker_inited = 1;

    LPC_SC->PCONP |= (1 << 16); // Enable RIT power/clock
    LPC_SC->PCLKSEL1 |= (0x3 << 26);
    
    LP_TIMER->RICTRL = 0xC; // set default value
    LP_TIMER->RICOMPVAL = lp_compare_value;
    LP_TIMER->RIMASK = 0;
    LP_TIMER->RICOUNTER = 0;// counter reset
    LP_TIMER->RICTRL |= 1;  // enable interrupt
    
    NVIC_SetVector(LP_TIMER_IRQn, (uint32_t)lptmr_isr);
    NVIC_EnableIRQ(LP_TIMER_IRQn);
}

uint32_t lp_ticker_read()
{
    if (!lp_ticker_inited) {
        lp_ticker_init();
    }
    return LP_TIMER->RICOUNTER;
}

uint32_t lp_ticker_get_overflows_counter(void)
{
    return overflows;
}

uint32_t lp_ticker_get_compare_match(void)
{
    return LP_TIMER->RICOMPVAL;
}

void lp_ticker_set_interrupt(uint32_t now, uint32_t time)
{
    now = lp_ticker_read();
    (void)now;
    LP_TIMER->RICOMPVAL = (time);
}

void lp_ticker_sleep_until(uint32_t now, uint32_t time)
{
    lp_ticker_set_interrupt(now, time);
    sleep_t sleep_obj;
    mbed_enter_sleep(&sleep_obj);
    mbed_exit_sleep(&sleep_obj);
}

#endif