nanospin_ns()

Busy-wait without blocking for a period of time

Synopsis:

#include <time.h>

int nanospin_ns( unsigned long nsec );

Arguments:

nsec: The number of nanoseconds that you want to busy-wait for.

Library:

libc

Use the -l c option to qcc to link against this library. This library is usually included automatically.

Description:

The nanospin_ns() function busy-waits for the number of nanoseconds specified in nsec, without blocking the calling thread.

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.

Because of the nature of time measurement, the function might actually wait longer than the specified time. For more information, see the Tick, Tock: Understanding the Neutrino Microkernel's Concept of Time chapter of the QNX Neutrino Programmer's Guide.

The first time you call nanospin_ns(), the C library invokes nanospin_calibrate() with an argument of 0 (interrupts enabled), if you haven't invoked it directly first.

Returns:

EOK: Success.
E2BIG: The delay specified by nsec is greater than 500 milliseconds.
A delay of more than a few milliseconds might not work on some processors. For longer delays, use the POSIX timer_*() functions.
EINTR: A too-high rate of interrupts occurred during the calibration routine.
ENOSYS: This system's startup-* program didn't initialize the timing information necessary to use nanospin_ns().

Classification:

QNX Neutrino

Safety:
Cancellation point	No
Interrupt handler	Read the Caveats
Signal handler	Yes
Thread	Yes

Caveats:

You should use busy-waiting only when absolutely necessary for accessing hardware.

It isn't safe to call this function in an interrupt handler if nanospin_calibrate() hasn't been called yet.