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/*
* Copyright (C) 2015 Kaspar Schleiser <kaspar@schleiser.de>
*
* 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.
*/
/**
* @defgroup sys_xtimer Timers
* @ingroup sys
* @brief Provides a high level timer module to register
* timers, get current system time, and let a thread sleep for
* a certain amount of time.
*
* The implementation takes one low-level timer that is supposed to run at 1MHz
* speed and multiplexes it.
*
* Insertion and removal of timers has O(n) complexity with (n) being the
* number of active timers. The reason for this is that multiplexing is
* realized by next-first singly linked lists.
*
* @{
* @file
* @brief xtimer interface definitions
* @author Kaspar Schleiser <kaspar@schleiser.de>
*/
#ifndef XTIMER_H
#define XTIMER_H
#include <stdint.h>
#include "msg.h"
#include "periph/timer.h"
#include "timex.h"
#include "board.h"
#include "periph_conf.h"
/**
* @brief internal define to allow using variables instead of defines
*/
#ifdef XTIMER_TRACE
#include "xtimer_trace.h"
#endif
#ifdef __cplusplus
extern "C" {
#endif
/**
* @brief xtimer callback type
*/
typedef void (*timer_callback_t)(void*);
/**
* @brief xtimer timer structure
*/
typedef struct xtimer {
struct xtimer *next; /**< reference to next timer in timer lists */
uint32_t target; /**< lower 32bit absolute target time */
uint32_t long_target; /**< upper 32bit absolute target time */
timer_callback_t callback; /**< callback function to call when timer
expires */
void *arg; /**< argument to pass to callback function */
} xtimer_t;
/**
* @brief get the current system time as 32bit microsecond value
*
* @note Overflows every ~71minutes, thus returns xtimer_now64() % 32,
* but is more efficient.
*
* @return current time as 32bit microsecond value
*/
static inline uint32_t xtimer_now(void);
/**
* @brief get the current system time as 64bit microsecond value
*
* @return current time as 64bit microsecond value
*/
uint64_t xtimer_now64(void);
/**
* @brief get the current system time into a timex_t
*
* @param[out] out pointer to timex_t the time will be written to
*/
void xtimer_now_timex(timex_t *out);
/**
* @brief xtimer initialization function
*
* This sets up xtimer. Has to be called once at system boot.
* If @ref auto_init is enabled, it will call this for you.
*/
void xtimer_init(void);
/**
* @brief Stop execution of a thread for some time
*
* When called from an ISR, this function will spin and thus block the MCU in
* interrupt context for the specified amount in *seconds*, so don't *ever* use
* it there.
*
* @param[in] seconds the amount of seconds the thread should sleep
*/
static void xtimer_sleep(uint32_t seconds);
/**
* @brief Stop execution of a thread for some time
*
* When called from an ISR, this function will spin and thus block the MCU for
* the specified amount in microseconds, so only use it there for *very* short
* periods, e.g., less than XTIMER_BACKOFF.
*
* @param[in] microseconds the amount of microseconds the thread should sleep
*/
static void xtimer_usleep(uint32_t microseconds);
/**
* @brief Stop execution of a thread for some time, 64bit version
*
* When called from an ISR, this function will spin and thus block the MCU for
* the specified amount in microseconds, so only use it there for *very* short
* periods, e.g., less then XTIMER_BACKOFF.
*
* @param[in] microseconds the amount of microseconds the thread should sleep
*/
static inline void xtimer_usleep64(uint64_t microseconds);
/**
* @brief Stop execution of a thread for some time
*
* Don't expect nanosecond accuracy. As of now, this function just calls
* xtimer_usleep(nanoseconds/1000).
*
* When called from an ISR, this function will spin-block, so only use it there
* for *very* short periods.
*
* @param[in] nanoseconds the amount of nanoseconds the thread should sleep
*/
static void xtimer_nanosleep(uint32_t nanoseconds);
/**
* @brief Stop execution of a thread for some time, blocking
*
* This function will spin-block, so only use it *very* short periods.
*
* @param[in] microseconds the amount of microseconds the thread should spin
*/
static inline void xtimer_spin(uint32_t microseconds);
/**
* @brief will cause the calling thread to be suspended until the absolute
* time (@p last_wakeup + @p interval).
*
* When the function returns, @p last_wakeup is set to
* (@p last_wakeup + @p interval).
*
* This function can be used to create periodic wakeups.
* @c last_wakeup should be set to xtimer_now() before first call of the
* function.
*
* If the result of (@p last_wakeup + usecs) would be in the past, the function
* sets @p last_wakeup to @p last_wakeup + @p interval and returns immediately.
*
* @param[in] last_wakeup base time for the wakeup
* @param[in] usecs time in microseconds that will be added to
* last_wakeup
*/
void xtimer_usleep_until(uint32_t *last_wakeup, uint32_t usecs);
/**
* @brief Set a timer that sends a message
*
* This function sets a timer that will send a message @p offset microseconds
* from now.
*
* The mesage struct specified by msg parameter will not be copied, e.g., it
* needs to point to valid memory until the message has been delivered.
*
* @param[in] timer timer struct to work with
* @param[in] offset microseconds from now
* @param[in] msg ptr to msg that will be sent
* @param[in] target_pid pid the message will be sent to
*/
void xtimer_set_msg(xtimer_t *timer, uint32_t offset, msg_t *msg, kernel_pid_t target_pid);
/**
* @brief Set a timer that sends a message, 64bit version
*
* This function sets a timer that will send a message @p offset microseconds
* from now.
*
* The mesage struct specified by msg parameter will not be copied, e.g., it
* needs to point to valid memory until the message has been delivered.
*
* @param[in] timer timer struct to work with
* @param[in] offset microseconds from now
* @param[in] msg ptr to msg that will be sent
* @param[in] target_pid pid the message will be sent to
*/
void xtimer_set_msg64(xtimer_t *timer, uint64_t offset, msg_t *msg, kernel_pid_t target_pid);
/**
* @brief Set a timer that wakes up a thread
*
* This function sets a timer that will wake up a thread when the timer has
* expired.
*
* @param[in] timer timer struct to work with
* @param[in] offset microseconds from now
* @param[in] pid pid of the thread that will be woken up
*/
void xtimer_set_wakeup(xtimer_t *timer, uint32_t offset, kernel_pid_t pid);
/**
* @brief Set a timer that wakes up a thread, 64bit version
*
* This function sets a timer that will wake up a thread when the timer has
* expired.
*
* @param[in] timer timer struct to work with
* @param[in] offset microseconds from now
* @param[in] pid pid of the thread that will be woken up
*/
void xtimer_set_wakeup64(xtimer_t *timer, uint64_t offset, kernel_pid_t pid);
/**
* @brief Set a timer to execute a callback at some time in the future
*
* Expects timer->callback to be set.
*
* The callback specified in the timer struct will be executed @p offset
* microseconds in the future.
*
* @warning BEWARE! Callbacks from xtimer_set() are being executed in interrupt
* context (unless offset < XTIMER_BACKOFF). DON'T USE THIS FUNCTION unless you
* know *exactly* what that means.
*
* @param[in] timer the timer structure to use
* @param[in] offset time in microseconds from now specifying that timer's
* callback's execution time
*/
void xtimer_set(xtimer_t *timer, uint32_t offset);
/**
* @brief remove a timer
*
* @note this function runs in O(n) with n being the number of active timers
*
* @param[in] timer ptr to timer structure that will be removed
*
* @return 1 on success
* @return 0 when timer was not active
*/
int xtimer_remove(xtimer_t *timer);
/**
* @brief receive a message blocking but with timeout
*
* @param[out] msg pointer to a msg_t which will be filled in case of
* no timeout
* @param[in] us timeout in microseconds relative
*
* @return < 0 on error, other value otherwise
*/
int xtimer_msg_receive_timeout(msg_t *msg, uint32_t us);
/**
* @brief receive a message blocking but with timeout, 64bit version
*
* @param[out] msg pointer to a msg_t which will be filled in case of no
* timeout
* @param[in] us timeout in microseconds relative
*
* @return < 0 on error, other value otherwise
*/
int xtimer_msg_receive_timeout64(msg_t *msg, uint64_t us);
/**
* @brief xtimer backoff value
*
* All timers that are less than XTIMER_BACKOFF microseconds in the future will
* just spin.
*
* This is supposed to be defined per-device in e.g., periph_conf.h.
*/
#ifndef XTIMER_BACKOFF
#define XTIMER_BACKOFF 30
#endif
/**
* @brief xtimer overhead value
*
* This value specifies the time a timer will be late if uncorrected, e.g.,
* the system-specific xtimer execution time from timer ISR to executing
* a timer's callback's first instruction.
*
* E.g., with XTIMER_OVERHEAD == 0
* start=xtimer_now();
* xtimer_set(&timer, X);
* (in callback:)
* overhead=xtimer_now()-start-X;
*
* xtimer automatically substracts XTIMER_OVERHEAD from a timer's target time,
* but when the timer triggers, xtimer will spin-lock until a timer's target
* time is reached, so timers will never trigger early.
*
* This is supposed to be defined per-device in e.g., periph_conf.h.
*/
#ifndef XTIMER_OVERHEAD
#define XTIMER_OVERHEAD 20
#endif
#ifndef XTIMER_ISR_BACKOFF
/**
* @brief xtimer isr backoff time
*
* When scheduling the next isr, if it is less than the backoff time
* in the future, just spin.
*
* This is supposed to be defined per-device in e.g., periph_conf.h.
*/
#define XTIMER_ISR_BACKOFF 20
#endif
/*
* @brief xtimer prescaler value
*
* xtimer assumes it is running with an underlying 1MHz timer.
* If the timer is slower by a power of two, XTIMER_SHIFT can be used to
* adjust the difference.
*
* This will also initialize the underlying periph timer with
* us_per_tick == (1<<XTIMER_SHIFT).
*
* For example, if the timer is running with 250khz, set XTIMER_SHIFT to 2.
*/
#ifndef XTIMER_SHIFT
#define XTIMER_SHIFT (0)
#endif
/**
* @brief set xtimer default timer configuration
* @{
*/
#ifndef XTIMER
#define XTIMER (0)
#define XTIMER_CHAN (0)
#if TIMER_0_MAX_VALUE == 0xffffff
#define XTIMER_MASK 0xff000000
#elif TIMER_0_MAX_VALUE == 0xffff
#define XTIMER_MASK 0xffff0000
#endif
#endif
/**
* @}
*/
#ifndef XTIMER_MASK
/**
* @brief xtimer timer mask
*
* This value specifies the mask relative to 0xffffffff that the used timer
* counts to, e.g., 0xffffffff & ~TIMER_MAXVALUE.
*
* For a 16bit timer, the mask would be 0xFFFF0000, for a 24bit timer, the mask
* would be 0xFF000000. Don't set this for 32bit timers.
*
* This is supposed to be defined per-device in e.g., periph_conf.h.
*/
#define XTIMER_MASK (0)
#endif
#define XTIMER_MASK_SHIFTED (XTIMER_MASK << XTIMER_SHIFT)
#ifndef XTIMER_USLEEP_UNTIL_OVERHEAD
/**
* @brief xtimer_usleep_until overhead value
*
* This value specifies the time a xtimer_usleep_until will be late
* if uncorrected.
*
* This is supposed to be defined per-device in e.g., periph_conf.h.
*/
#define XTIMER_USLEEP_UNTIL_OVERHEAD 10
#endif
#if XTIMER_MASK
extern volatile uint32_t _high_cnt;
#endif
/**
* @brief IPC message type for xtimer msg callback
*/
#define MSG_XTIMER 12345
/**
* @brief returns the (masked) low-level timer counter value.
*/
static inline uint32_t _lltimer_now(void)
{
#if XTIMER_SHIFT
return ((uint32_t)timer_read(XTIMER)) << XTIMER_SHIFT;
#else
return timer_read(XTIMER);
#endif
}
/**
* @brief drop bits of a value that don't fit into the low-level timer.
*/
static inline uint32_t _lltimer_mask(uint32_t val)
{
return val & ~XTIMER_MASK_SHIFTED;
}
/**
* @{
* @brief xtimer internal stuff
* @internal
*/
int _xtimer_set_absolute(xtimer_t *timer, uint32_t target);
void _xtimer_set64(xtimer_t *timer, uint32_t offset, uint32_t long_offset);
void _xtimer_sleep(uint32_t offset, uint32_t long_offset);
static inline void xtimer_spin_until(uint32_t value);
/** @} */
#if XTIMER_MASK
#ifndef XTIMER_SHIFT_ON_COMPARE
/**
* @brief ignore some bits when comparing timer values
*
* (only relevant when XTIMER_MASK != 0, e.g., timers < 32bit.)
*
* When combining _lltimer_now() and _high_cnt, we have to get the same value in
* order to work around a race between overflowing _lltimer_now() and OR'ing the
* resulting values.
* But some platforms are too slow to get the same timer
* value twice, so we use this define to ignore some of the bits.
*
* Use tests/xtimer_shift_on_compare to find the correct value for your MCU.
*/
#define XTIMER_SHIFT_ON_COMPARE (0)
#endif
#endif
#ifndef XTIMER_MIN_SPIN
/**
* @brief Minimal value xtimer_spin() can spin
*/
#define XTIMER_MIN_SPIN (1<<XTIMER_SHIFT)
#endif
static inline uint32_t xtimer_now(void)
{
#if XTIMER_MASK
uint32_t a, b;
do {
a = _lltimer_now() | _high_cnt;
b = _lltimer_now() | _high_cnt;
} while ((a >> XTIMER_SHIFT_ON_COMPARE) != (b >> XTIMER_SHIFT_ON_COMPARE));
return b;
#else
return _lltimer_now();
#endif
}
static inline void xtimer_spin_until(uint32_t target) {
#if XTIMER_MASK
target = _lltimer_mask(target);
#endif
while (_lltimer_now() > target);
while (_lltimer_now() < target);
}
static inline void xtimer_spin(uint32_t offset) {
uint32_t start = _lltimer_now();
while ((_lltimer_now() - start) < offset);
}
static inline void xtimer_usleep(uint32_t microseconds)
{
_xtimer_sleep(microseconds, 0);
}
static inline void xtimer_usleep64(uint64_t microseconds)
{
_xtimer_sleep((uint32_t) microseconds, (uint32_t) (microseconds >> 32));
}
static inline void xtimer_sleep(uint32_t seconds)
{
xtimer_usleep64((uint64_t)seconds * SEC_IN_USEC);
}
static inline void xtimer_nanosleep(uint32_t nanoseconds)
{
_xtimer_sleep(nanoseconds / USEC_IN_NS, 0);
}
#ifdef __cplusplus
}
#endif
/** @} */
#endif /* XTIMER_H */