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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
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    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!
 
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    contact details.
 
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*/
 
/* 
 
Changes from V2.6.0
 
	+ AVR port - Replaced the inb() and outb() functions with direct memory
	  access.  This allows the port to be built with the 20050414 build of
	  WinAVR.
*/
 
#include <stdlib.h>
#include <avr/interrupt.h>
 
#include "FreeRTOS.h"
#include "task.h"
 
/*-----------------------------------------------------------
 * Implementation of functions defined in portable.h for the AVR 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 )
 
/*-----------------------------------------------------------*/
 
/* We require the address of the pxCurrentTCB variable, but don't want to know
any details of its type. */
typedef void tskTCB;
extern volatile tskTCB * volatile pxCurrentTCB;
 
/*-----------------------------------------------------------*/
 
/* 
 * Macro to save all the general purpose registers, the save the stack pointer
 * into the TCB.  
 * 
 * The first thing we do is save the flags then disable interrupts.  This is to 
 * guard our stack against having a context switch interrupt after we have already 
 * pushed the registers onto the stack - causing the 32 registers to be on the 
 * stack twice. 
 * 
 * r1 is set to zero as the compiler expects it to be thus, however some
 * of the math routines make use of R1. 
 * 
 * The interrupts will have been disabled during the call to portSAVE_CONTEXT()
 * so we need not worry about reading/writing to the stack pointer. 
 */
 
#define portSAVE_CONTEXT()									\
	asm volatile (	"push	r0						\n\t"	\
					"in		r0, __SREG__			\n\t"	\
					"cli							\n\t"	\
					"push	r0						\n\t"	\
					"push	r1						\n\t"	\
					"clr	r1						\n\t"	\
					"push	r2						\n\t"	\
					"push	r3						\n\t"	\
					"push	r4						\n\t"	\
					"push	r5						\n\t"	\
					"push	r6						\n\t"	\
					"push	r7						\n\t"	\
					"push	r8						\n\t"	\
					"push	r9						\n\t"	\
					"push	r10						\n\t"	\
					"push	r11						\n\t"	\
					"push	r12						\n\t"	\
					"push	r13						\n\t"	\
					"push	r14						\n\t"	\
					"push	r15						\n\t"	\
					"push	r16						\n\t"	\
					"push	r17						\n\t"	\
					"push	r18						\n\t"	\
					"push	r19						\n\t"	\
					"push	r20						\n\t"	\
					"push	r21						\n\t"	\
					"push	r22						\n\t"	\
					"push	r23						\n\t"	\
					"push	r24						\n\t"	\
					"push	r25						\n\t"	\
					"push	r26						\n\t"	\
					"push	r27						\n\t"	\
					"push	r28						\n\t"	\
					"push	r29						\n\t"	\
					"push	r30						\n\t"	\
					"push	r31						\n\t"	\
					"lds	r26, pxCurrentTCB		\n\t"	\
					"lds	r27, pxCurrentTCB + 1	\n\t"	\
					"in		r0, 0x3d				\n\t"	\
					"st		x+, r0					\n\t"	\
					"in		r0, 0x3e				\n\t"	\
					"st		x+, r0					\n\t"	\
				);
 
/* 
 * Opposite to portSAVE_CONTEXT().  Interrupts will have been disabled during
 * the context save so we can write to the stack pointer. 
 */
 
#define portRESTORE_CONTEXT()								\
	asm volatile (	"lds	r26, pxCurrentTCB		\n\t"	\
					"lds	r27, pxCurrentTCB + 1	\n\t"	\
					"ld		r28, x+					\n\t"	\
					"out	__SP_L__, r28			\n\t"	\
					"ld		r29, x+					\n\t"	\
					"out	__SP_H__, r29			\n\t"	\
					"pop	r31						\n\t"	\
					"pop	r30						\n\t"	\
					"pop	r29						\n\t"	\
					"pop	r28						\n\t"	\
					"pop	r27						\n\t"	\
					"pop	r26						\n\t"	\
					"pop	r25						\n\t"	\
					"pop	r24						\n\t"	\
					"pop	r23						\n\t"	\
					"pop	r22						\n\t"	\
					"pop	r21						\n\t"	\
					"pop	r20						\n\t"	\
					"pop	r19						\n\t"	\
					"pop	r18						\n\t"	\
					"pop	r17						\n\t"	\
					"pop	r16						\n\t"	\
					"pop	r15						\n\t"	\
					"pop	r14						\n\t"	\
					"pop	r13						\n\t"	\
					"pop	r12						\n\t"	\
					"pop	r11						\n\t"	\
					"pop	r10						\n\t"	\
					"pop	r9						\n\t"	\
					"pop	r8						\n\t"	\
					"pop	r7						\n\t"	\
					"pop	r6						\n\t"	\
					"pop	r5						\n\t"	\
					"pop	r4						\n\t"	\
					"pop	r3						\n\t"	\
					"pop	r2						\n\t"	\
					"pop	r1						\n\t"	\
					"pop	r0						\n\t"	\
					"out	__SREG__, r0			\n\t"	\
					"pop	r0						\n\t"	\
				);
 
/*-----------------------------------------------------------*/
 
/*
 * Perform hardware setup to enable ticks from timer 1, compare match A.
 */
static void prvSetupTimerInterrupt( void );
/*-----------------------------------------------------------*/
 
/* 
 * See header file for description. 
 */
portSTACK_TYPE *pxPortInitialiseStack( portSTACK_TYPE *pxTopOfStack, pdTASK_CODE pxCode, void *pvParameters )
{
unsigned short usAddress;
 
	/* 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--;
 
	/* Simulate how the stack would look after a call to vPortYield() generated by 
	the compiler. */
 
	/*lint -e950 -e611 -e923 Lint doesn't like this much - but nothing I can do about it. */
 
	/* The start of the task code will be popped off the stack last, so place
	it on first. */
	usAddress = ( unsigned short ) pxCode;
	*pxTopOfStack = ( portSTACK_TYPE ) ( usAddress & ( unsigned short ) 0x00ff );
	pxTopOfStack--;
 
	usAddress >>= 8;
	*pxTopOfStack = ( portSTACK_TYPE ) ( usAddress & ( unsigned short ) 0x00ff );
	pxTopOfStack--;
 
	/* 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--;
 
 
	/* Now the remaining registers.   The compiler expects R1 to be 0. */
	*pxTopOfStack = ( portSTACK_TYPE ) 0x00;	/* 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--;
	*pxTopOfStack = ( portSTACK_TYPE ) 0x16;	/* R16 */
	pxTopOfStack--;
	*pxTopOfStack = ( portSTACK_TYPE ) 0x17;	/* R17 */
	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--;
 
	/* 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 ) 0x26;	/* R26 X */
	pxTopOfStack--;
	*pxTopOfStack = ( portSTACK_TYPE ) 0x27;	/* R27 */
	pxTopOfStack--;
	*pxTopOfStack = ( portSTACK_TYPE ) 0x28;	/* R28 Y */
	pxTopOfStack--;
	*pxTopOfStack = ( portSTACK_TYPE ) 0x29;	/* R29 */
	pxTopOfStack--;
	*pxTopOfStack = ( portSTACK_TYPE ) 0x30;	/* R30 Z */
	pxTopOfStack--;
	*pxTopOfStack = ( portSTACK_TYPE ) 0x031;	/* R31 */
	pxTopOfStack--;
 
	/*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. */
	portRESTORE_CONTEXT();
 
	/* Simulate a function call end as generated by the compiler.  We will now
	jump to the start of the task the context of which we have just restored. */
	asm volatile ( "ret" );
 
	/* 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. */
}
/*-----------------------------------------------------------*/
 
/*
 * Manual context switch.  The first thing we do is save the registers so we
 * can use a naked attribute.
 */
void vPortYield( void ) __attribute__ ( ( naked ) );
void vPortYield( void )
{
	portSAVE_CONTEXT();
	vTaskSwitchContext();
	portRESTORE_CONTEXT();
 
	asm volatile ( "ret" );
}
/*-----------------------------------------------------------*/
 
/*
 * Context switch function used by the tick.  This must be identical to 
 * vPortYield() from the call to vTaskSwitchContext() onwards.  The only
 * difference from vPortYield() is the tick count is incremented as the
 * call comes from the tick ISR.
 */
void vPortYieldFromTick( void ) __attribute__ ( ( naked ) );
void vPortYieldFromTick( void )
{
	portSAVE_CONTEXT();
	vTaskIncrementTick();
	vTaskSwitchContext();
	portRESTORE_CONTEXT();
 
	asm volatile ( "ret" );
}
/*-----------------------------------------------------------*/
 
/*
 * 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. */
	ucLowByte = TIMSK;
	ucLowByte |= portCOMPARE_MATCH_A_INTERRUPT_ENABLE;
	TIMSK = ucLowByte;
}
/*-----------------------------------------------------------*/
 
#if configUSE_PREEMPTION == 1
 
	/*
	 * Tick ISR for preemptive scheduler.  We can use a naked attribute as
	 * the context is saved at the start of vPortYieldFromTick().  The tick
	 * count is incremented after the context is saved.
	 */
	void SIG_OUTPUT_COMPARE1A( void ) __attribute__ ( ( signal, naked ) );
	void SIG_OUTPUT_COMPARE1A( void )
	{
		vPortYieldFromTick();
		asm volatile ( "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();
	 */
	void SIG_OUTPUT_COMPARE1A( void ) __attribute__ ( ( signal ) );
	void SIG_OUTPUT_COMPARE1A( void )
	{
		vTaskIncrementTick();
	}
#endif