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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.

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*/

#include <stdlib.h>

#include "FreeRTOS.h"

#include "task.h"

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

 * Implementation of functions defined in portable.h for the AVR/IAR port.

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

/* Start tasks with interrupts enables. */

#define portFLAGS_INT_ENABLED                                   ( ( portSTACK_TYPE ) 0x80 )

/* Hardware constants for timer 1. */

#define portCLEAR_COUNTER_ON_MATCH                              ( ( unsigned char ) 0x08 )

#define portPRESCALE_64                                                 ( ( unsigned char ) 0x03 )

#define portCLOCK_PRESCALER                                             ( ( unsigned long ) 64 )

#define portCOMPARE_MATCH_A_INTERRUPT_ENABLE    ( ( unsigned char ) 0x10 )

/* The number of bytes used on the hardware stack by the task start address. */

#define portBYTES_USED_BY_RETURN_ADDRESS                ( 2 )

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

/* Stores the critical section nesting.  This must not be initialised to 0.

It will be initialised when a task starts. */

#define portNO_CRITICAL_NESTING                                 ( ( unsigned portBASE_TYPE ) 0 )

unsigned portBASE_TYPE uxCriticalNesting = 0x50;

/*

 * Perform hardware setup to enable ticks from timer 1, compare match A.

 */

static void prvSetupTimerInterrupt( void );

/*

 * The IAR compiler does not have full support for inline assembler, so

 * these are defined in the portmacro assembler file.

 */

extern void vPortYieldFromTick( void );

extern void vPortStart( void );

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

/*

 * See header file for description.

 */

portSTACK_TYPE *pxPortInitialiseStack( portSTACK_TYPE *pxTopOfStack, pdTASK_CODE pxCode, void *pvParameters )

{

unsigned short usAddress;

portSTACK_TYPE *pxTopOfHardwareStack;

        /* Place a few bytes of known values on the bottom of the stack.

        This is just useful for debugging. */

        *pxTopOfStack = 0x11;

        pxTopOfStack--;

        *pxTopOfStack = 0x22;

        pxTopOfStack--;

        *pxTopOfStack = 0x33;

        pxTopOfStack--;

        /* Remember where the top of the hardware stack is - this is required

        below. */

        pxTopOfHardwareStack = pxTopOfStack;

        /* Simulate how the stack would look after a call to vPortYield(). */

        /*lint -e950 -e611 -e923 Lint doesn't like this much - but nothing I can do about it. */

        /* The IAR compiler requires two stacks per task.  First there is the

        hardware call stack which uses the AVR stack pointer.  Second there is the

        software stack (local variables, parameter passing, etc.) which uses the

        AVR Y register.

        This function places both stacks within the memory block passed in as the

        first parameter.  The hardware stack is placed at the bottom of the memory

        block.  A gap is then left for the hardware stack to grow.  Next the software

        stack is placed.  The amount of space between the software and hardware

        stacks is defined by configCALL_STACK_SIZE.

        The first part of the stack is the hardware stack.  Place the start

        address of the task on the hardware stack. */

        usAddress = ( unsigned short ) pxCode;

        *pxTopOfStack = ( portSTACK_TYPE ) ( usAddress & ( unsigned short ) 0x00ff );

        pxTopOfStack--;

        usAddress >>= 8;

        *pxTopOfStack = ( portSTACK_TYPE ) ( usAddress & ( unsigned short ) 0x00ff );

        pxTopOfStack--;

        /* Leave enough space for the hardware stack before starting the software

        stack.  The '- 2' is because we have already used two spaces for the

        address of the start of the task. */

        pxTopOfStack -= ( configCALL_STACK_SIZE - 2 );

        /* Next simulate the stack as if after a call to portSAVE_CONTEXT().

        portSAVE_CONTEXT places the flags on the stack immediately after r0

        to ensure the interrupts get disabled as soon as possible, and so ensuring

        the stack use is minimal should a context switch interrupt occur. */

        *pxTopOfStack = ( portSTACK_TYPE ) 0x00;        /* R0 */

        pxTopOfStack--;

        *pxTopOfStack = portFLAGS_INT_ENABLED;

        pxTopOfStack--;

        /* Next place the address of the hardware stack.  This is required so

        the AVR stack pointer can be restored to point to the hardware stack. */

        pxTopOfHardwareStack -= portBYTES_USED_BY_RETURN_ADDRESS;

        usAddress = ( unsigned short ) pxTopOfHardwareStack;

        /* SPL */

        *pxTopOfStack = ( portSTACK_TYPE ) ( usAddress & ( unsigned short ) 0x00ff );

        pxTopOfStack--;

        /* SPH */

        usAddress >>= 8;

        *pxTopOfStack = ( portSTACK_TYPE ) ( usAddress & ( unsigned short ) 0x00ff );

        pxTopOfStack--;

        /* Now the remaining registers. */

        *pxTopOfStack = ( portSTACK_TYPE ) 0x01;        /* R1 */

        pxTopOfStack--;

        *pxTopOfStack = ( portSTACK_TYPE ) 0x02;        /* R2 */

        pxTopOfStack--;

        *pxTopOfStack = ( portSTACK_TYPE ) 0x03;        /* R3 */

        pxTopOfStack--;

        *pxTopOfStack = ( portSTACK_TYPE ) 0x04;        /* R4 */

        pxTopOfStack--;

        *pxTopOfStack = ( portSTACK_TYPE ) 0x05;        /* R5 */

        pxTopOfStack--;

        *pxTopOfStack = ( portSTACK_TYPE ) 0x06;        /* R6 */

        pxTopOfStack--;

        *pxTopOfStack = ( portSTACK_TYPE ) 0x07;        /* R7 */

        pxTopOfStack--;

        *pxTopOfStack = ( portSTACK_TYPE ) 0x08;        /* R8 */

        pxTopOfStack--;

        *pxTopOfStack = ( portSTACK_TYPE ) 0x09;        /* R9 */

        pxTopOfStack--;

        *pxTopOfStack = ( portSTACK_TYPE ) 0x10;        /* R10 */

        pxTopOfStack--;

        *pxTopOfStack = ( portSTACK_TYPE ) 0x11;        /* R11 */

        pxTopOfStack--;

        *pxTopOfStack = ( portSTACK_TYPE ) 0x12;        /* R12 */

        pxTopOfStack--;

        *pxTopOfStack = ( portSTACK_TYPE ) 0x13;        /* R13 */

        pxTopOfStack--;

        *pxTopOfStack = ( portSTACK_TYPE ) 0x14;        /* R14 */

        pxTopOfStack--;

        *pxTopOfStack = ( portSTACK_TYPE ) 0x15;        /* R15 */

        pxTopOfStack--;

        /* Place the parameter on the stack in the expected location. */

        usAddress = ( unsigned short ) pvParameters;

        *pxTopOfStack = ( portSTACK_TYPE ) ( usAddress & ( unsigned short ) 0x00ff );

        pxTopOfStack--;

        usAddress >>= 8;

        *pxTopOfStack = ( portSTACK_TYPE ) ( usAddress & ( unsigned short ) 0x00ff );

        pxTopOfStack--;

        *pxTopOfStack = ( portSTACK_TYPE ) 0x18;        /* R18 */

        pxTopOfStack--;

        *pxTopOfStack = ( portSTACK_TYPE ) 0x19;        /* R19 */

        pxTopOfStack--;

        *pxTopOfStack = ( portSTACK_TYPE ) 0x20;        /* R20 */

        pxTopOfStack--;

        *pxTopOfStack = ( portSTACK_TYPE ) 0x21;        /* R21 */

        pxTopOfStack--;

        *pxTopOfStack = ( portSTACK_TYPE ) 0x22;        /* R22 */

        pxTopOfStack--;

        *pxTopOfStack = ( portSTACK_TYPE ) 0x23;        /* R23 */

        pxTopOfStack--;

        *pxTopOfStack = ( portSTACK_TYPE ) 0x24;        /* R24 */

        pxTopOfStack--;

        *pxTopOfStack = ( portSTACK_TYPE ) 0x25;        /* R25 */

        pxTopOfStack--;

        *pxTopOfStack = ( portSTACK_TYPE ) 0x26;        /* R26 X */

        pxTopOfStack--;

        *pxTopOfStack = ( portSTACK_TYPE ) 0x27;        /* R27 */

        pxTopOfStack--;

        /* The Y register is not stored as it is used as the software stack and

        gets saved into the task control block. */

        *pxTopOfStack = ( portSTACK_TYPE ) 0x30;        /* R30 Z */

        pxTopOfStack--;

        *pxTopOfStack = ( portSTACK_TYPE ) 0x031;       /* R31 */

        pxTopOfStack--;

        *pxTopOfStack = portNO_CRITICAL_NESTING;        /* Critical nesting is zero when the task starts. */

        /*lint +e950 +e611 +e923 */

        return pxTopOfStack;

}

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

portBASE_TYPE xPortStartScheduler( void )

{

        /* Setup the hardware to generate the tick. */

        prvSetupTimerInterrupt();

        /* Restore the context of the first task that is going to run.

        Normally we would just call portRESTORE_CONTEXT() here, but as the IAR

        compiler does not fully support inline assembler we have to make a call.*/

        vPortStart();

        /* Should not get here! */

        return pdTRUE;

}

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

void vPortEndScheduler( void )

{

        /* It is unlikely that the AVR port will get stopped.  If required simply

        disable the tick interrupt here. */

}

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

/*

 * Setup timer 1 compare match A to generate a tick interrupt.

 */

static void prvSetupTimerInterrupt( void )

{

unsigned long ulCompareMatch;

unsigned char ucHighByte, ucLowByte;

        /* Using 16bit timer 1 to generate the tick.  Correct fuses must be

        selected for the configCPU_CLOCK_HZ clock. */

        ulCompareMatch = configCPU_CLOCK_HZ / configTICK_RATE_HZ;

        /* We only have 16 bits so have to scale to get our required tick rate. */

        ulCompareMatch /= portCLOCK_PRESCALER;

        /* Adjust for correct value. */

        ulCompareMatch -= ( unsigned long ) 1;

        /* Setup compare match value for compare match A.  Interrupts are disabled

        before this is called so we need not worry here. */

        ucLowByte = ( unsigned char ) ( ulCompareMatch & ( unsigned long ) 0xff );

        ulCompareMatch >>= 8;

        ucHighByte = ( unsigned char ) ( ulCompareMatch & ( unsigned long ) 0xff );

        OCR1AH = ucHighByte;

        OCR1AL = ucLowByte;

        /* Setup clock source and compare match behaviour. */

        ucLowByte = portCLEAR_COUNTER_ON_MATCH | portPRESCALE_64;

        TCCR1B = ucLowByte;

        /* Enable the interrupt - this is okay as interrupt are currently globally

        disabled. */

        TIMSK |= portCOMPARE_MATCH_A_INTERRUPT_ENABLE;

}

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

#if configUSE_PREEMPTION == 1

        /*

         * Tick ISR for preemptive scheduler.  We can use a __task attribute as

         * the context is saved at the start of vPortYieldFromTick().  The tick

         * count is incremented after the context is saved.

         */

        __task void SIG_OUTPUT_COMPARE1A( void )

        {

                vPortYieldFromTick();

                asm( "reti" );

        }

#else

        /*

         * Tick ISR for the cooperative scheduler.  All this does is increment the

         * tick count.  We don't need to switch context, this can only be done by

         * manual calls to taskYIELD();

         *

         * THE INTERRUPT VECTOR IS POPULATED IN portmacro.s90.  DO NOT INSTALL

         * IT HERE USING THE USUAL PRAGMA.

         */

        __interrupt void SIG_OUTPUT_COMPARE1A( void )

        {

                vTaskIncrementTick();

        }

#endif

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

void vPortEnterCritical( void )

{

        portDISABLE_INTERRUPTS();

        uxCriticalNesting++;

}

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

void vPortExitCritical( void )

{

        uxCriticalNesting--;

        if( uxCriticalNesting == portNO_CRITICAL_NESTING )

        {

                portENABLE_INTERRUPTS();

        }

}