Sleep

NuttX provides three different types of sleep interfaces.

Common Sleep Interfaces

Scheduled Sleep Interfaces (tick-based)

Suspend the calling thread for a specified amount of time until the time expires or the thread is explicitly woken up through scheduler operations.

void nxsched_ticksleep(unsigned int ticks)

Suspends the calling thread from execution for the specified number of system ticks.

Parameters:

  • ticks – The number of system ticks to sleep.

void nxsched_usleep(useconds_t usec)

Suspends the calling thread from execution for the specified number of microseconds.

Parameters:

  • usec – The number of microseconds to sleep.

void nxsched_msleep(unsigned int msec)

Suspends the calling thread from execution for the specified number of milliseconds.

Parameters:

  • msec – The number of milliseconds to sleep.

void nxsched_sleep(unsigned int sec)

Suspends the calling thread from execution for the specified number of seconds.

Parameters:

  • sec – The number of seconds to sleep.

int nxsched_nanosleep(const struct timespec *rqtp, struct timespec *rmtp)

Suspends the calling thread from execution for the specified rqtp argument. This function will return the remaining time via updating rmtp if the sleep is interrupted by a signal.

Parameters:

  • rqtp – The amount of time to be suspended from execution.

  • rmtp – If the rmtp argument is non-NULL, the timespec structure referenced by it is updated to contain the amount of time remaining.

Returns:

0 (OK), or negated errno if unsuccessful.

void nxsched_wakeup(struct tcb_s *tcb)

This function is used to wake up a thread that is currently in sleeping state before its timeout expires.

Parameters:

  • tcb – Pointer to the TCB of the task to be awakened.

Signal-based Sleep Interfaces (timespec-based)

Suspend the calling thread for a specified amount of time until the time expires or a signal is delivered to the calling thread.

Note

Implementations are dependent on the signal framework and based on standard timespec conversion.

void nxsig_usleep(useconds_t usec)

Suspends the calling thread from execution for the specified number of microseconds.

Parameters:

  • usec – The number of microseconds to sleep.

void nxsig_sleep(unsigned int sec)

Suspends the calling thread from execution for the specified number of seconds.

Parameters:

  • sec – The number of seconds to sleep.

int nxsig_nanosleep(const struct timespec *rqtp, struct timespec *rmtp)

Suspends the calling thread from execution for the specified rqtp argument. This function will return the remaining time via updating rmtp if the sleep is interrupted by a signal.

Parameters:

  • rqtp – The amount of time to be suspended from execution.

  • rmtp – If the rmtp argument is non-NULL, the timespec structure referenced by it is updated to contain the amount of time remaining.

Returns:

0 (OK), or negated errno if unsuccessful.

Busy Sleep Interfaces

Spin in a loop for the requested duration and never yield the CPU. The delay accuracy depends on CONFIG_BOARD_LOOPSPERMSEC.

void up_mdelay(unsigned int milliseconds)

Delay inline for the requested number of milliseconds.

Parameters:

  • milliseconds – The number of milliseconds to delay.

void up_udelay(useconds_t microseconds)

Delay inline for the requested number of microseconds.

Parameters:

  • microseconds – The number of microseconds to delay.

void up_ndelay(unsigned long nanoseconds)

Delay inline for the requested number of nanoseconds.

Parameters:

  • nanoseconds – The number of nanoseconds to delay.