FreeRTOS-Kernel/Source/portable/MPLAB/PIC24_dsPIC/port.c

/*
    FreeRTOS V6.0.1 - Copyright (C) 2009 Real Time Engineers Ltd.

    ***************************************************************************
    *                                                                         *
    * If you are:                                                             *
    *                                                                         *
    *    + New to FreeRTOS,                                                   *
    *    + Wanting to learn FreeRTOS or multitasking in general quickly       *
    *    + Looking for basic training,                                        *
    *    + Wanting to improve your FreeRTOS skills and productivity           *
    *                                                                         *
    * then take a look at the FreeRTOS eBook                                  *
    *                                                                         *
    *        "Using the FreeRTOS Real Time Kernel - a Practical Guide"        *
    *                  http://www.FreeRTOS.org/Documentation                  *
    *                                                                         *
    * A pdf reference manual is also available.  Both are usually delivered   *
    * to your inbox within 20 minutes to two hours when purchased between 8am *
    * and 8pm GMT (although please allow up to 24 hours in case of            *
    * exceptional circumstances).  Thank you for your support!                *
    *                                                                         *
    ***************************************************************************

    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.

    http://www.OpenRTOS.com - Commercial support, development, porting,
    licensing and training services.
*/

/*
	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;

	/* 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
}