port.c

FreeRTOSV3.2.0 经典嵌入式操作系统

/*
	FreeRTOS V3.2.0 - Copyright (C) 2003 - 2005 Richard Barry.

	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 as published by
	the Free Software Foundation; either version 2 of the License, or
	(at your option) any later version.

	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
	along with FreeRTOS; if not, write to the Free Software
	Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA

	A special exception to the GPL can be applied should you wish to distribute
	a combined work that includes FreeRTOS, without being obliged to provide
	the source code for any proprietary components.  See the licensing section
	of http://www.FreeRTOS.org for full details of how and when the exception
	can be applied.

	***************************************************************************
	See http://www.FreeRTOS.org for documentation, latest information, license
	and contact details.  Please ensure to read the configuration and relevant
	port sections of the online documentation.
	***************************************************************************
*/

#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 portCHAR ) 0x08 )
#define portPRESCALE_64							( ( unsigned portCHAR ) 0x03 )
#define portCLOCK_PRESCALER						( ( unsigned portLONG ) 64 )
#define portCOMPARE_MATCH_A_INTERRUPT_ENABLE	( ( unsigned portCHAR ) 0x10 )

/* The number of bytes used on the hardware stack by the task start address. */
#define portBYTES_USED_BY_RETURN_ADDRESS		( 2 )
/*-----------------------------------------------------------*/

/*
 * 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 portSHORT 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 portSHORT ) pxCode;
	*pxTopOfStack = ( portSTACK_TYPE ) ( usAddress & ( unsigned portSHORT ) 0x00ff );
	pxTopOfStack--;

	usAddress >>= 8;
	*pxTopOfStack = ( portSTACK_TYPE ) ( usAddress & ( unsigned portSHORT ) 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 portSHORT ) pxTopOfHardwareStack;

	/* SPL */
	*pxTopOfStack = ( portSTACK_TYPE ) ( usAddress & ( unsigned portSHORT ) 0x00ff );
	pxTopOfStack--;

	/* SPH */
	usAddress >>= 8;
	*pxTopOfStack = ( portSTACK_TYPE ) ( usAddress & ( unsigned portSHORT ) 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 portSHORT ) pvParameters;
	*pxTopOfStack = ( portSTACK_TYPE ) ( usAddress & ( unsigned portSHORT ) 0x00ff );
	pxTopOfStack--;

	usAddress >>= 8;
	*pxTopOfStack = ( portSTACK_TYPE ) ( usAddress & ( unsigned portSHORT ) 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 */

	/*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 portLONG ulCompareMatch;
unsigned portCHAR 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 portLONG ) 1;

	/* Setup compare match value for compare match A.  Interrupts are disabled
	before this is called so we need not worry here. */
	ucLowByte = ( unsigned portCHAR ) ( ulCompareMatch & ( unsigned portLONG ) 0xff );
	ulCompareMatch >>= 8;
	ucHighByte = ( unsigned portCHAR ) ( ulCompareMatch & ( unsigned portLONG ) 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