src/rp2_common/hardware_timer/include/hardware/timer.h

/*
 * Copyright (c) 2020 Raspberry Pi (Trading) Ltd.
 *
 * SPDX-License-Identifier: BSD-3-Clause
 */

#ifndef _HARDWARE_TIMER_H
#define _HARDWARE_TIMER_H

#include "pico.h"
#include "hardware/structs/timer.h"

#ifdef __cplusplus
extern "C" {
#endif

/** \file hardware/timer.h
 *  \defgroup hardware_timer hardware_timer
 *
 * Low-level hardware timer API
 *
 * This API provides medium level access to the timer HW.
 * See also \ref pico_time which provides higher levels functionality using the hardware timer.
 *
 * The timer peripheral on RP2040 supports the following features:
 *  - single 64-bit counter, incrementing once per microsecond
 *  - Latching two-stage read of counter, for race-free read over 32 bit bus
 *  - Four alarms: match on the lower 32 bits of counter, IRQ on match.
 *
 * By default the timer uses a one microsecond reference that is generated in the Watchdog (see Section 4.8.2) which is derived
 * from the clk_ref.
 *
 * The timer has 4 alarms, and can output a separate interrupt for each alarm. The alarms match on the lower 32 bits of the 64
 * bit counter which means they can be fired a maximum of 2^32 microseconds into the future. This is equivalent to:
 *  - 2^32 ÷ 10^6: ~4295 seconds
 *  - 4295 ÷ 60: ~72 minutes
 *
 * The timer is expected to be used for short sleeps, if you want a longer alarm see the \ref hardware_rtc functions.
 *
 * \subsection timer_example Example
 * \addtogroup hardware_timer
 *
 * \include hello_timer.c
 *
 * \see pico_time
 */

// PICO_CONFIG: PARAM_ASSERTIONS_ENABLED_TIMER, Enable/disable assertions in the timer module, type=bool, default=0, group=hardware_timer
#ifndef PARAM_ASSERTIONS_ENABLED_TIMER
#define PARAM_ASSERTIONS_ENABLED_TIMER 0
#endif

static inline void check_hardware_alarm_num_param(uint alarm_num) {
    invalid_params_if(TIMER, alarm_num >= NUM_TIMERS);
}

/*! \brief Return a 32 bit timestamp value in microseconds
*  \ingroup hardware_timer
*
* Returns the low 32 bits of the hardware timer.
* \note This value wraps roughly every 1 hour 11 minutes and 35 seconds.
*
* \return the 32 bit timestamp
*/
static inline uint32_t time_us_32() {
    return timer_hw->timerawl;
}

/*! \brief Return the current 64 bit timestamp value in microseconds
*  \ingroup hardware_timer
*
* Returns the full 64 bits of the hardware timer. The \ref pico_time and other functions rely on the fact that this
* value monotonically increases from power up. As such it is expected that this value counts upwards and never wraps
* (we apologize for introducing a potential year 5851444 bug).
*
* \return the 64 bit timestamp
*/
uint64_t time_us_64();

/*! \brief Busy wait wasting cycles for the given (32 bit) number of microseconds
 *  \ingroup hardware_timer
 *
 * \param delay_us delay amount
 */
void busy_wait_us_32(uint32_t delay_us);

/*! \brief Busy wait wasting cycles for the given (64 bit) number of microseconds
 *  \ingroup hardware_timer
 *
 * \param delay_us delay amount
 */
void busy_wait_us(uint64_t delay_us);

/*! \brief Busy wait wasting cycles until after the specified timestamp
 *  \ingroup hardware_timer
 *
 * \param t Absolute time to wait until
 */
void busy_wait_until(absolute_time_t t);

/*! \brief Check if the specified timestamp has been reached
 *  \ingroup hardware_timer
 *
 * \param t Absolute time to compare against current time
 * \return true if it is now after the specified timestamp
 */
static inline bool time_reached(absolute_time_t t) {
    uint64_t target = to_us_since_boot(t);
    uint32_t hi_target = target >> 32u;
    uint32_t hi = timer_hw->timerawh;
    return (hi >= hi_target && (timer_hw->timerawl >= (uint32_t) target || hi != hi_target));
}

/*! Callback function type for hardware alarms
 *  \ingroup hardware_timer
 *
 * \param alarm_num the hardware alarm number
 * \sa hardware_alarm_set_callback
 */
typedef void (*hardware_alarm_callback_t)(uint alarm_num);

/*! \brief cooperatively claim the use of this hardware alarm_num
 *  \ingroup hardware_timer
 *
 * This method hard asserts if the hardware alarm is currently claimed.
 *
 * \param alarm_num the hardware alarm to claim
 * \sa hardware_claiming
 */
void hardware_alarm_claim(uint alarm_num);

/*! \brief cooperatively release the claim on use of this hardware alarm_num
 *  \ingroup hardware_timer
 *
 * \param alarm_num the hardware alarm to unclaim
 * \sa hardware_claiming
 */
void hardware_alarm_unclaim(uint alarm_num);

/*! \brief Enable/Disable a callback for a hardware timer on this core
 *  \ingroup hardware_timer
 *
 * This method enables/disables the alarm IRQ for the specified hardware alarm on the
 * calling core, and set the specified callback to be associated with that alarm.
 *
 * This callback will be used for the timeout set via hardware_alarm_set_target
 *
 * \note This will install the handler on the current core if the IRQ handler isn't already set.
 * Therefore the user has the opportunity to call this up from the core of their choice
 *
 * \param alarm_num the hardware alarm number
 * \param callback the callback to install, or NULL to unset
 *
 * \sa hardware_alarm_set_target
 */
void hardware_alarm_set_callback(uint alarm_num, hardware_alarm_callback_t callback);

/**
 * \brief Set the current target for the specified hardware alarm
 *
 * This will replace any existing target
 *
 * @param alarm_num the hardware alarm number
 * @param t the target timestamp
 * @return true if the target was "missed"; i.e. it was in the past, or occurred before a future hardware timeout could be set
 */
bool hardware_alarm_set_target(uint alarm_num, absolute_time_t t);

/**
 * \brief Cancel an existing target (if any) for a given hardware_alarm
 *
 * @param alarm_num
 */

void hardware_alarm_cancel(uint alarm_num);

#ifdef __cplusplus
}
#endif
#endif