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delay milisecond

Hi all Iam using STR912FW44 based board and I want a delay function that should give the delay in milisecond I made a function


void delay_ms (unsigned long nCount){   /* Wait function                    */
  nCount=nCount+16000000L;

  while (nCount--);
}

when I call

delay_ms(10000);

it gives arround 10 second delay but when I call

delay_ms(20000);
it should give arround 20 second delay but it does not happen

but when I call

delay_ms(10000);
delay_ms(10000);

it gives arround 15 sec delay

please tell me exact way to build a delay function

regards
rupesh

Parents

0 Catcus Blip over 16 years ago

things to take into account:
* you are not using a hardware timer, so haw can you guarantee anything? your code depends on how fast the CPU can crunch instructions, not the frequency of a peripheral designed to help you (hence a hardware timer).
* you are using C to write a delay loop - which makes you sensitive to optimization, compiler whims etc. use assembly for exact delays.

/*
** Copyright (C) 2008 Tamir Michael
**
** This program is free software; you can redistribute it and/or modify
** it under the terms of the GNU General Public License as published by
** the Free Software Foundation; either version 2 of the License, or
** (at your option) any later version.
**
** This program is distributed in the hope that it will be useful,
** but WITHOUT ANY WARRANTY; without even the implied warranty of
** MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
** GNU General Public License for more details.
**
** You should have received a copy of the GNU General Public License
** along with this program; if not, write to the Free Software
** Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
*/

#ifndef __TIMER_H
#define __TIMER_H

#include "general_definitions.h"

#define TIMER_TICKING     1
#define TIMER_NOT_TICKING 2

typedef enum
{
        e_timer_not_ticking = 0,
        e_timer_ticking,
        e_timer_expired
} timer_state ;

typedef enum
{
        e_timer_poll_mode,
        e_timer_exact_period_mode,
        e_timer_exact_oneshot_mode
} timer_mode ;

typedef struct
{
        timer_state             state ; // 0 means not ticking, 1 means ticking
        timer_mode              mode ;
        callback_ptr    callback ;
        int32s                  *callback_parameter ;
        int32u                  deadline_countdown ; // a user provided timeout in units of 10 milliseconds
        int32u                  late_counter ; // this user provided flag is incremented every 10 milliseconds to indicate how late the timer actually was
        int32u                  period ;
} timer_t ;

typedef struct
{
        callback_ptr callback ;
        int32s           *parameter ;
} timer_callback_prop_t ;

void    timer_module_init(void) ;
int32s  timer_poll(int32s, int32s, int32s *) ;
int32s  timer_exact(int32s, int32s, timer_callback_prop_t, timer_mode) ;
int32s  timer_stop(int32s) ;
void    timer_stop_all(void) ;
int32u  timer_ticks_remaining(int32s) ;

void    TIM1_callback(void) ;

#endif

Reply

0 Catcus Blip over 16 years ago

/*
** Copyright (C) 2008 Tamir Michael
**
** This program is free software; you can redistribute it and/or modify
** it under the terms of the GNU General Public License as published by
** the Free Software Foundation; either version 2 of the License, or
** (at your option) any later version.
**
** This program is distributed in the hope that it will be useful,
** but WITHOUT ANY WARRANTY; without even the implied warranty of
** MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
** GNU General Public License for more details.
**
** You should have received a copy of the GNU General Public License
** along with this program; if not, write to the Free Software
** Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
*/

#ifndef __TIMER_H
#define __TIMER_H

#include "general_definitions.h"

#define TIMER_TICKING     1
#define TIMER_NOT_TICKING 2

typedef enum
{
        e_timer_not_ticking = 0,
        e_timer_ticking,
        e_timer_expired
} timer_state ;

typedef enum
{
        e_timer_poll_mode,
        e_timer_exact_period_mode,
        e_timer_exact_oneshot_mode
} timer_mode ;

typedef struct
{
        timer_state             state ; // 0 means not ticking, 1 means ticking
        timer_mode              mode ;
        callback_ptr    callback ;
        int32s                  *callback_parameter ;
        int32u                  deadline_countdown ; // a user provided timeout in units of 10 milliseconds
        int32u                  late_counter ; // this user provided flag is incremented every 10 milliseconds to indicate how late the timer actually was
        int32u                  period ;
} timer_t ;

typedef struct
{
        callback_ptr callback ;
        int32s           *parameter ;
} timer_callback_prop_t ;

void    timer_module_init(void) ;
int32s  timer_poll(int32s, int32s, int32s *) ;
int32s  timer_exact(int32s, int32s, timer_callback_prop_t, timer_mode) ;
int32s  timer_stop(int32s) ;
void    timer_stop_all(void) ;
int32u  timer_ticks_remaining(int32s) ;

void    TIM1_callback(void) ;

#endif

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