/*
    FreeRTOS V7.2.0 - Copyright (C) 2012 Real Time Engineers Ltd.
	

    ***************************************************************************
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     *    professional grade, cross platform, de facto standard solutions    *
     *    for microcontrollers - completely free of charge!                  *
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     *    >>> See http://www.FreeRTOS.org/Documentation for details. <<<     *
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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 modification to the GPL is included to allow you to
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    License and the FreeRTOS license exception along with FreeRTOS; if not it
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    by writing to Richard Barry, contact details for whom are available on the
    FreeRTOS WEB site.

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    ***************************************************************************
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    license and contact details.
    
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*/

/*
	Changes from V4.2.1

	+ Introduced the configKERNEL_INTERRUPT_PRIORITY definition.
*/

/*-----------------------------------------------------------
 * Implementation of functions defined in portable.h for the PIC24 port.
 *----------------------------------------------------------*/

/* Scheduler include files. */
#include "FreeRTOS.h"
#include "task.h"

/* Hardware specifics. */
#define portBIT_SET 1
#define portTIMER_PRESCALE 8
#define portINITIAL_SR	0

/* Defined for backward compatability with project created prior to 
FreeRTOS.org V4.3.0. */
#ifndef configKERNEL_INTERRUPT_PRIORITY
	#define configKERNEL_INTERRUPT_PRIORITY 1
#endif

/* The program counter is only 23 bits. */
#define portUNUSED_PR_BITS	0x7f

/* Records the nesting depth of calls to portENTER_CRITICAL(). */
unsigned portBASE_TYPE uxCriticalNesting = 0xef;

#if configKERNEL_INTERRUPT_PRIORITY != 1
	#error If configKERNEL_INTERRUPT_PRIORITY is not 1 then the #32 in the following macros needs changing to equal the portINTERRUPT_BITS value, which is ( configKERNEL_INTERRUPT_PRIORITY << 5 )
#endif

#ifdef MPLAB_PIC24_PORT

	#define portRESTORE_CONTEXT()																						\
		asm volatile(	"MOV	_pxCurrentTCB, W0		\n"	/* Restore the stack pointer for the task. */				\
						"MOV	[W0], W15				\n"																\
						"POP	W0						\n"	/* Restore the critical nesting counter for the task. */	\
						"MOV	W0, _uxCriticalNesting	\n"																\
						"POP	PSVPAG					\n"																\
						"POP	CORCON					\n"																\
						"POP	TBLPAG					\n"																\
						"POP	RCOUNT					\n"	/* Restore the registers from the stack. */					\
						"POP	W14						\n"																\
						"POP.D	W12						\n"																\
						"POP.D	W10						\n"																\
						"POP.D	W8						\n"																\
						"POP.D	W6						\n"																\
						"POP.D	W4						\n"																\
						"POP.D	W2						\n"																\
						"POP.D	W0						\n"																\
						"POP	SR						  " );

#endif /* MPLAB_PIC24_PORT */

#ifdef MPLAB_DSPIC_PORT

	#define portRESTORE_CONTEXT()																						\
		asm volatile(	"MOV	_pxCurrentTCB, W0		\n"	/* Restore the stack pointer for the task. */				\
						"MOV	[W0], W15				\n"																\
						"POP	W0						\n"	/* Restore the critical nesting counter for the task. */	\
						"MOV	W0, _uxCriticalNesting	\n"																\
						"POP	PSVPAG					\n"																\
						"POP	CORCON					\n"																\
						"POP	DOENDH					\n"																\
						"POP	DOENDL					\n"																\
						"POP	DOSTARTH				\n"																\
						"POP	DOSTARTL				\n"																\
						"POP	DCOUNT					\n"																\
						"POP	ACCBU					\n"																\
						"POP	ACCBH					\n"																\
						"POP	ACCBL					\n"																\
						"POP	ACCAU					\n"																\
						"POP	ACCAH					\n"																\
						"POP	ACCAL					\n"																\
						"POP	TBLPAG					\n"																\
						"POP	RCOUNT					\n"	/* Restore the registers from the stack. */					\
						"POP	W14						\n"																\
						"POP.D	W12						\n"																\
						"POP.D	W10						\n"																\
						"POP.D	W8						\n"																\
						"POP.D	W6						\n"																\
						"POP.D	W4						\n"																\
						"POP.D	W2						\n"																\
						"POP.D	W0						\n"																\
						"POP	SR						  " );

#endif /* MPLAB_DSPIC_PORT */

/*
 * Setup the timer used to generate the tick interrupt.
 */
static void prvSetupTimerInterrupt( void );

/* 
 * See header file for description. 
 */
portSTACK_TYPE *pxPortInitialiseStack( portSTACK_TYPE *pxTopOfStack, pdTASK_CODE pxCode, void *pvParameters )
{
unsigned short usCode;
portBASE_TYPE i;

const portSTACK_TYPE xInitialStack[] = 
{
	0x1111,	/* W1 */
	0x2222, /* W2 */
	0x3333, /* W3 */
	0x4444, /* W4 */
	0x5555, /* W5 */
	0x6666, /* W6 */
	0x7777, /* W7 */
	0x8888, /* W8 */
	0x9999, /* W9 */
	0xaaaa, /* W10 */
	0xbbbb, /* W11 */
	0xcccc, /* W12 */
	0xdddd, /* W13 */
	0xeeee, /* W14 */
	0xcdce, /* RCOUNT */
	0xabac, /* TBLPAG */

	/* dsPIC specific registers. */
	#ifdef MPLAB_DSPIC_PORT
		0x0202, /* ACCAL */
		0x0303, /* ACCAH */
		0x0404, /* ACCAU */
		0x0505, /* ACCBL */
		0x0606, /* ACCBH */
		0x0707, /* ACCBU */
		0x0808, /* DCOUNT */
		0x090a, /* DOSTARTL */
		0x1010, /* DOSTARTH */
		0x1110, /* DOENDL */
		0x1212, /* DOENDH */
	#endif
};

	/* Setup the stack as if a yield had occurred.

	Save the low bytes of the program counter. */
	usCode = ( unsigned short ) pxCode;
	*pxTopOfStack = ( portSTACK_TYPE ) usCode;
	pxTopOfStack++;

	/* Save the high byte of the program counter.  This will always be zero
	here as it is passed in a 16bit pointer.  If the address is greater than
	16 bits then the pointer will point to a jump table. */
	*pxTopOfStack = ( portSTACK_TYPE ) 0;
	pxTopOfStack++;

	/* Status register with interrupts enabled. */
	*pxTopOfStack = portINITIAL_SR;
	pxTopOfStack++;

	/* Parameters are passed in W0. */
	*pxTopOfStack = ( portSTACK_TYPE ) pvParameters;
	pxTopOfStack++;

	for( i = 0; i < ( sizeof( xInitialStack ) / sizeof( portSTACK_TYPE ) ); i++ )
	{
		*pxTopOfStack = xInitialStack[ i ];
		pxTopOfStack++;
	}

	*pxTopOfStack = CORCON;
	pxTopOfStack++;
	*pxTopOfStack = PSVPAG;
	pxTopOfStack++;

	/* Finally the critical nesting depth. */
	*pxTopOfStack = 0x00;
	pxTopOfStack++;

	return pxTopOfStack;
}
/*-----------------------------------------------------------*/

portBASE_TYPE xPortStartScheduler( void )
{
	/* Setup a timer for the tick ISR. */
	prvSetupTimerInterrupt(); 

	/* Restore the context of the first task to run. */
	portRESTORE_CONTEXT();

	/* Simulate the end of the yield function. */
	asm volatile ( "return" );

	/* Should not reach here. */
	return pdTRUE;
}
/*-----------------------------------------------------------*/

void vPortEndScheduler( void )
{
	/* It is unlikely that the scheduler for the PIC port will get stopped
	once running.  If required disable the tick interrupt here, then return 
	to xPortStartScheduler(). */
}
/*-----------------------------------------------------------*/

/*
 * Setup a timer for a regular tick.
 */
static void prvSetupTimerInterrupt( void )
{
const unsigned long ulCompareMatch = ( ( configCPU_CLOCK_HZ / portTIMER_PRESCALE ) / configTICK_RATE_HZ ) - 1;

	/* Prescale of 8. */
	T1CON = 0;
	TMR1 = 0;

	PR1 = ( unsigned short ) ulCompareMatch;

	/* Setup timer 1 interrupt priority. */
	IPC0bits.T1IP = configKERNEL_INTERRUPT_PRIORITY;

	/* Clear the interrupt as a starting condition. */
	IFS0bits.T1IF = 0;

	/* Enable the interrupt. */
	IEC0bits.T1IE = 1;

	/* Setup the prescale value. */
	T1CONbits.TCKPS0 = 1;
	T1CONbits.TCKPS1 = 0;

	/* Start the timer. */
	T1CONbits.TON = 1;
}
/*-----------------------------------------------------------*/

void vPortEnterCritical( void )
{
	portDISABLE_INTERRUPTS();
	uxCriticalNesting++;
}
/*-----------------------------------------------------------*/

void vPortExitCritical( void )
{
	uxCriticalNesting--;
	if( uxCriticalNesting == 0 )
	{
		portENABLE_INTERRUPTS();
	}
}
/*-----------------------------------------------------------*/

void __attribute__((__interrupt__, auto_psv)) _T1Interrupt( void )
{
	/* Clear the timer interrupt. */
	IFS0bits.T1IF = 0;

	vTaskIncrementTick();

	#if configUSE_PREEMPTION == 1
		portYIELD();
	#endif
}