RIOT/cpu/nrf51822/periph/rtt.c

/*
 * Copyright (C) 2014 Freie Universität Berlin
 *
 * This file is subject to the terms and conditions of the GNU Lesser General
 * Public License v2.1. See the file LICENSE in the top level directory for more
 * details.
 */

/**
 * @ingroup     cpu_nrf51822
 * @{
 *
 * @file        rtt.c
 * @brief       Real-time timer driver implementation
 *
 * @author      Hauke Petersen <hauke.petersen@fu-berlin.de>
 *
 * @}
 */

#include <stdlib.h>
#include <stdio.h>

#include "cpu.h"
#include "board.h"
#include "sched.h"
#include "thread.h"
#include "periph_conf.h"
#include "periph/rtt.h"

/* guard file in case no RTC device was specified */
#if RTT_NUMOF

/*
 * callback and argument for an active alarm
 */
static rtt_alarm_cb_t alarm_cb;
static void *alarm_arg;

void rtt_init(void)
{
    rtt_poweron();

    /* configure interrupt */
    NVIC_SetPriority(RTT_IRQ, RTT_IRQ_PRIO);
    NVIC_EnableIRQ(RTT_IRQ);

    /* set prescaler */
    RTT_DEV->PRESCALER = RTT_PRESCALER;

    /* enable the low-frequency clock */
    NRF_CLOCK->TASKS_LFCLKSTART = 1;

    /* start the actual RTT thing */
    RTT_DEV->TASKS_START = 1;
}

uint32_t rtt_get_counter(void)
{
    return RTT_DEV->COUNTER;
}

void rtt_set_counter(uint32_t counter)
{
    /* not supported for the NRF51822? -> could not find out how to do this */
}

void rtt_set_alarm(uint32_t alarm, rtt_alarm_cb_t cb, void *arg)
{
    alarm_cb = cb;
    alarm_arg = arg;
    RTT_DEV->CC[0] = (alarm & RTT_MAX_VALUE);
    RTT_DEV->INTENSET = RTC_INTENSET_COMPARE0_Msk;
}

uint32_t rtt_get_alarm(void)
{
    return RTT_DEV->CC[0];
}

void rtt_clear_alarm(void)
{
    RTT_DEV->INTENCLR = RTC_INTENSET_COMPARE0_Msk;
}

void rtt_poweron(void)
{
    RTT_DEV->POWER = 1;
}

void rtt_poweroff(void)
{
    RTT_DEV->POWER = 0;
}

__attribute__((naked)) void RTT_ISR(void)
{
    ISR_ENTER();
    if (RTT_DEV->EVENTS_COMPARE[0] ==1) {
        RTT_DEV->EVENTS_COMPARE[0] = 0;
        RTT_DEV->INTENCLR = RTC_INTENSET_COMPARE0_Msk;
        alarm_cb(alarm_arg);
    }
    if (sched_context_switch_request) {
        thread_yield();
    }
    ISR_EXIT();
}

#endif /* RTT_NUMOF */