nanospin_calibrate()

Выполнить калибровку перед вызовом nanospin*()

Прототип:

#include <time.h>
int nanospin_calibrate( int disable );

Аргументы:

disable
1 to disable interrupts during the call to nanospin_calibrate(), or 0 to enable them.

Библиотека:

libc

Описание:

The nanospin_calibrate() function performs the calibration for the nanospin*() family of delay functions. The first time that you call nanospin(), nanospin_ns(), or nanospin_ns_to_count(), the C library invokes nanospin_calibrate() with an argument of 0 (interrupts enabled), unless you call it directly first.


Note: If you don't directly invoke nanospin_calibrate(), the first nanospin*() call in a process will have an overly long delay.

The nanospin*() functions are designed for use with hardware that requires short time delays between accesses. You should use them to delay only for times less than a few milliseconds. For longer delays, use the POSIX timer_*() functions.


Interrupts occurring during nanospin_calibrate() can throw off its timings. If disable is 0 (zero), you can prevent this situation by:

  1. letting the thread acquire I/O privilege
  2. disabling the interrupts around the nanospin_calibrate() call.

If disable is 1 (one), the code disables interrupts around the calibration loop(s). The calling thread is still responsible for obtaining I/O privilege before calling nanospin_calibrate().

Возвращаемое значение:

EOK
Успешное завершение.
EINTR
A too-high rate of interrupts occurred during the calibration routine.
EPERM
The process doesn't have superuser capabilities.

Примеры:

Busy-wait for 100 nanoseconds:

#include <time.h>
#include <sys/syspage.h>
int disable = 0;
unsigned long time = 100;
...
/* Wake up the hardware, then wait for it to be ready. */
if ( (nanospin_calibrate( disable )) == EOK )
nanospin_count( nanospin_ns_to_count( time ) );
else
printf ("Didn't calibrate successfully.\n");
/* Use the hardware. */
...

Классификация:

ЗОСРВ «Нейтрино»

Точка остановки потока
Нет
Обработчик прерываний
Нет
Обработчик сигналов
Да
В потоке
Да

Тематические ссылки:

nanospin(), nanospin_count(), nanospin_ns(), nanospin_ns_to_count(), timer_create()




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