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/*

    FreeRTOS V6.1.1 - Copyright (C) 2011 Real Time Engineers Ltd.

    ***************************************************************************

    *                                                                         *

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    ***************************************************************************

    This file is part of the FreeRTOS distribution.

    FreeRTOS is free software; you can redistribute it and/or modify it under

    the terms of the GNU General Public License (version 2) as published by the

    Free Software Foundation AND MODIFIED BY the FreeRTOS exception.

    ***NOTE*** The exception to the GPL is included to allow you to distribute

    a combined work that includes FreeRTOS without being obliged to provide the

    source code for proprietary components outside of the FreeRTOS kernel.

    FreeRTOS 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 and the FreeRTOS license exception along with FreeRTOS; if not it

    can be viewed here: http://www.freertos.org/a00114.html and also obtained

    by writing to Richard Barry, contact details for whom are available on the

    FreeRTOS WEB site.

    1 tab == 4 spaces!

    http://www.FreeRTOS.org - Documentation, latest information, license and

    contact details.

    http://www.SafeRTOS.com - A version that is certified for use in safety

    critical systems.

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    licensing and training services.

*/

/* High speed timer test as described in main.c. */

/* Scheduler includes. */

#include "FreeRTOS.h"

/* Library includes. */

#include "stm32f10x_lib.h"

#include "stm32f10x_tim.h"

#include "stm32f10x_map.h"

/* The set frequency of the interrupt.  Deviations from this are measured as

the jitter. */

#define timerINTERRUPT_FREQUENCY                ( ( unsigned portSHORT ) 20000 )

/* The expected time between each of the timer interrupts - if the jitter was

zero. */

#define timerEXPECTED_DIFFERENCE_VALUE  ( configCPU_CLOCK_HZ / timerINTERRUPT_FREQUENCY )

/* The highest available interrupt priority. */

#define timerHIGHEST_PRIORITY                   ( 0 )

/* Misc defines. */

#define timerMAX_32BIT_VALUE                    ( 0xffffffffUL )

#define timerTIMER_1_COUNT_VALUE                ( * ( ( unsigned long * ) ( TIMER1_BASE + 0x48 ) ) )

/* The number of interrupts to pass before we start looking at the jitter. */

#define timerSETTLE_TIME                        5

/*-----------------------------------------------------------*/

/*

 * Configures the two timers used to perform the test.

 */

void vSetupTimerTest( void );

/* Interrupt handler in which the jitter is measured. */

void vTimer2IntHandler( void );

/* Stores the value of the maximum recorded jitter between interrupts. */

volatile unsigned portSHORT usMaxJitter = 0;

/*-----------------------------------------------------------*/

void vSetupTimerTest( void )

{

unsigned long ulFrequency;

TIM_TimeBaseInitTypeDef  TIM_TimeBaseStructure;

NVIC_InitTypeDef NVIC_InitStructure;

        /* Enable timer clocks */

        RCC_APB1PeriphClockCmd( RCC_APB1Periph_TIM2, ENABLE );

        RCC_APB1PeriphClockCmd( RCC_APB1Periph_TIM3, ENABLE );

        /* Initialise data. */

        TIM_DeInit( TIM2 );

        TIM_DeInit( TIM3 );

        TIM_TimeBaseStructInit( &TIM_TimeBaseStructure );

        /* Time base configuration for timer 2 - which generates the interrupts. */

        ulFrequency = configCPU_CLOCK_HZ / timerINTERRUPT_FREQUENCY;

        TIM_TimeBaseStructure.TIM_Period = ( unsigned portSHORT ) ( ulFrequency & 0xffffUL );

        TIM_TimeBaseStructure.TIM_Prescaler = 0x0;

        TIM_TimeBaseStructure.TIM_ClockDivision = 0x0;

        TIM_TimeBaseStructure.TIM_CounterMode = TIM_CounterMode_Up;

        TIM_TimeBaseInit( TIM2, &TIM_TimeBaseStructure );

        TIM_ARRPreloadConfig( TIM2, ENABLE );

        /* Configuration for timer 3 which is used as a high resolution time

        measurement. */

        TIM_TimeBaseStructure.TIM_Period = ( unsigned portSHORT ) 0xffff;

        TIM_TimeBaseInit( TIM3, &TIM_TimeBaseStructure );

        TIM_ARRPreloadConfig( TIM3, ENABLE );

        /* Enable TIM2 IT.  TIM3 does not generate an interrupt. */

        NVIC_InitStructure.NVIC_IRQChannel = TIM2_IRQChannel;

        NVIC_InitStructure.NVIC_IRQChannelSubPriority = 0;

        NVIC_InitStructure.NVIC_IRQChannelPreemptionPriority = timerHIGHEST_PRIORITY;

        NVIC_InitStructure.NVIC_IRQChannelCmd = ENABLE;

        NVIC_Init( &NVIC_InitStructure );

        TIM_ITConfig( TIM2, TIM_IT_Update, ENABLE );

        /* Finally, enable both timers. */

        TIM_Cmd( TIM2, ENABLE );

        TIM_Cmd( TIM3, ENABLE );

}

/*-----------------------------------------------------------*/

void vTimer2IntHandler( void )

{

static unsigned portSHORT usLastCount = 0, usSettleCount = 0, usMaxDifference = 0;

unsigned portSHORT usThisCount, usDifference;

        /* Capture the free running timer 3 value as we enter the interrupt. */

        usThisCount = TIM3->CNT;

        if( usSettleCount >= timerSETTLE_TIME )

        {

                /* What is the difference between the timer value in this interrupt

                and the value from the last interrupt. */

                usDifference = usThisCount - usLastCount;

                /* Store the difference in the timer values if it is larger than the

                currently stored largest value.  The difference over and above the

                expected difference will give the 'jitter' in the processing of these

                interrupts. */

                if( usDifference > usMaxDifference )

                {

                        usMaxDifference = usDifference;

                        usMaxJitter = usMaxDifference - timerEXPECTED_DIFFERENCE_VALUE;

                }

        }

        else

        {

                /* Don't bother storing any values for the first couple of

                interrupts. */

                usSettleCount++;

        }

        /* Remember what the timer value was this time through, so we can calculate

        the difference the next time through. */

        usLastCount = usThisCount;

    TIM_ClearITPendingBit( TIM2, TIM_IT_Update );

}