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/****************************************************************************
* arch/avr/src/common/up_udelay.c
*
* Copyright (C) 2010 Gregory Nutt. All rights reserved.
* Author: Gregory Nutt <gnutt@nuttx.org>
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
*
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in
* the documentation and/or other materials provided with the
* distribution.
* 3. Neither the name NuttX nor the names of its contributors may be
* used to endorse or promote products derived from this software
* without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
* FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
* COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
* BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
* OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
* AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
* ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
* POSSIBILITY OF SUCH DAMAGE.
*
****************************************************************************/
/****************************************************************************
* Included Files
****************************************************************************/
#include <nuttx/config.h>
#include <sys/types.h>
#include <nuttx/arch.h>
/****************************************************************************
* Definitions
****************************************************************************/
#define CONFIG_BOARD_LOOPSPER100USEC ((CONFIG_BOARD_LOOPSPERMSEC+5)/10)
#define CONFIG_BOARD_LOOPSPER10USEC ((CONFIG_BOARD_LOOPSPERMSEC+50)/100)
#define CONFIG_BOARD_LOOPSPERUSEC ((CONFIG_BOARD_LOOPSPERMSEC+500)/1000)
/****************************************************************************
* Private Types
****************************************************************************/
/****************************************************************************
* Private Function Prototypes
****************************************************************************/
/****************************************************************************
* Private Variables
****************************************************************************/
/****************************************************************************
* Private Functions
****************************************************************************/
/****************************************************************************
* Public Functions
****************************************************************************/
/****************************************************************************
* Name: up_udelay
*
* Description:
* Delay inline for the requested number of microseconds. NOTE: Because
* of all of the setup, several microseconds will be lost before the actual
* timing looop begins. Thus, the delay will always be a few microseconds
* longer than requested.
*
* *** NOT multi-tasking friendly ***
*
* ASSUMPTIONS:
* The setting CONFIG_BOARD_LOOPSPERMSEC has been calibrated
*
****************************************************************************/
void up_udelay(useconds_t microseconds)
{
volatile int i;
/* We'll do this a little at a time because we expect that the
* CONFIG_BOARD_LOOPSPERUSEC is very inaccurate during to truncation in
* the divisions of its calculation. We'll use the largest values that
* we can in order to prevent significant error buildup in the loops.
*/
while (microseconds > 1000)
{
for (i = 0; i < CONFIG_BOARD_LOOPSPERMSEC; i++)
{
}
microseconds -= 1000;
}
while (microseconds > 100)
{
for (i = 0; i < CONFIG_BOARD_LOOPSPER100USEC; i++)
{
}
microseconds -= 100;
}
while (microseconds > 10)
{
for (i = 0; i < CONFIG_BOARD_LOOPSPER10USEC; i++)
{
}
microseconds -= 10;
}
while (microseconds > 0)
{
for (i = 0; i < CONFIG_BOARD_LOOPSPERUSEC; i++)
{
}
microseconds--;
}
}
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