root/webserver/example/EnergyMeters/Source/portable/GCC/ARM7_LPC23xx/port.c

/*
        FreeRTOS V5.4.1 - Copyright (C) 2009 Real Time Engineers Ltd.

        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.  
        Alternative commercial license and support terms are also available upon 
        request.  See the licensing section of http://www.FreeRTOS.org for full 
        license details.

        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.


        ***************************************************************************
        *                                                                         *
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        * See http://www.FreeRTOS.org/Documentation for details                   *
        *                                                                         *
        ***************************************************************************

        1 tab == 4 spaces!

        Please ensure to read the configuration and relevant port sections of the
        online documentation.

        http://www.FreeRTOS.org - Documentation, latest information, license and
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*/


/*-----------------------------------------------------------
 * Implementation of functions defined in portable.h for the ARM7 port.
 *
 * Components that can be compiled to either ARM or THUMB mode are
 * contained in this file.  The ISR routines, which can only be compiled
 * to ARM mode are contained in portISR.c.
 *----------------------------------------------------------*/


/* Standard includes. */
#include <stdlib.h>

/* Scheduler includes. */
#include "FreeRTOS.h"
#include "task.h"

/* Constants required to setup the task context. */
#define portINITIAL_SPSR                                ( ( portSTACK_TYPE ) 0x1f ) /* System mode, ARM mode, interrupts enabled. */
#define portTHUMB_MODE_BIT                              ( ( portSTACK_TYPE ) 0x20 )
#define portINSTRUCTION_SIZE                    ( ( portSTACK_TYPE ) 4 )
#define portNO_CRITICAL_SECTION_NESTING ( ( portSTACK_TYPE ) 0 )

/* Constants required to setup the tick ISR. */
#define portENABLE_TIMER                ( ( unsigned portCHAR ) 0x01 )
#define portPRESCALE_VALUE              0x00
#define portINTERRUPT_ON_MATCH          ( ( unsigned portLONG ) 0x01 )
#define portRESET_COUNT_ON_MATCH        ( ( unsigned portLONG ) 0x02 )

/* Constants required to setup the VIC for the tick ISR. */
#define portTIMER_VIC_CHANNEL           ( ( unsigned portLONG ) 0x0004 )
#define portTIMER_VIC_CHANNEL_BIT       ( ( unsigned portLONG ) 0x0010 )
#define portTIMER_VIC_ENABLE            ( ( unsigned portLONG ) 0x0020 )

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

/* Setup the timer to generate the tick interrupts. */
static void prvSetupTimerInterrupt( void );

/* 
 * The scheduler can only be started from ARM mode, so 
 * vPortISRStartFirstSTask() is defined in portISR.c. 
 */
extern void vPortISRStartFirstTask( void );

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

/* 
 * Initialise the stack of a task to look exactly as if a call to 
 * portSAVE_CONTEXT had been called.
 *
 * See header file for description. 
 */
portSTACK_TYPE *pxPortInitialiseStack( portSTACK_TYPE *pxTopOfStack, pdTASK_CODE pxCode, void *pvParameters )
{
portSTACK_TYPE *pxOriginalTOS;

        pxOriginalTOS = pxTopOfStack;

        /* Setup the initial stack of the task.  The stack is set exactly as 
        expected by the portRESTORE_CONTEXT() macro. */

        /* First on the stack is the return address - which in this case is the
        start of the task.  The offset is added to make the return address appear
        as it would within an IRQ ISR. */
        *pxTopOfStack = ( portSTACK_TYPE ) pxCode + portINSTRUCTION_SIZE;               
        pxTopOfStack--;

        *pxTopOfStack = ( portSTACK_TYPE ) 0x00000000;  /* R14 */
        pxTopOfStack--; 
        *pxTopOfStack = ( portSTACK_TYPE ) pxOriginalTOS; /* Stack used when task starts goes in R13. */
        pxTopOfStack--;
        *pxTopOfStack = ( portSTACK_TYPE ) 0x12121212;  /* R12 */
        pxTopOfStack--; 
        *pxTopOfStack = ( portSTACK_TYPE ) 0x11111111;  /* R11 */
        pxTopOfStack--; 
        *pxTopOfStack = ( portSTACK_TYPE ) 0x10101010;  /* R10 */
        pxTopOfStack--; 
        *pxTopOfStack = ( portSTACK_TYPE ) 0x09090909;  /* R9 */
        pxTopOfStack--; 
        *pxTopOfStack = ( portSTACK_TYPE ) 0x08080808;  /* R8 */
        pxTopOfStack--; 
        *pxTopOfStack = ( portSTACK_TYPE ) 0x07070707;  /* R7 */
        pxTopOfStack--; 
        *pxTopOfStack = ( portSTACK_TYPE ) 0x06060606;  /* R6 */
        pxTopOfStack--; 
        *pxTopOfStack = ( portSTACK_TYPE ) 0x05050505;  /* R5 */
        pxTopOfStack--; 
        *pxTopOfStack = ( portSTACK_TYPE ) 0x04040404;  /* R4 */
        pxTopOfStack--; 
        *pxTopOfStack = ( portSTACK_TYPE ) 0x03030303;  /* R3 */
        pxTopOfStack--; 
        *pxTopOfStack = ( portSTACK_TYPE ) 0x02020202;  /* R2 */
        pxTopOfStack--; 
        *pxTopOfStack = ( portSTACK_TYPE ) 0x01010101;  /* R1 */
        pxTopOfStack--; 

        /* When the task starts is will expect to find the function parameter in
        R0. */
        *pxTopOfStack = ( portSTACK_TYPE ) pvParameters; /* R0 */
        pxTopOfStack--;

        /* The last thing onto the stack is the status register, which is set for
        system mode, with interrupts enabled. */
        *pxTopOfStack = ( portSTACK_TYPE ) portINITIAL_SPSR;

        #ifdef THUMB_INTERWORK
        {
                /* We want the task to start in thumb mode. */
                *pxTopOfStack |= portTHUMB_MODE_BIT;
        }
        #endif

        pxTopOfStack--;

        /* Some optimisation levels use the stack differently to others.  This 
        means the interrupt flags cannot always be stored on the stack and will
        instead be stored in a variable, which is then saved as part of the
        tasks context. */
        *pxTopOfStack = portNO_CRITICAL_SECTION_NESTING;

        return pxTopOfStack;
}
/*-----------------------------------------------------------*/

portBASE_TYPE xPortStartScheduler( void )
{
        /* Start the timer that generates the tick ISR.  Interrupts are disabled
        here already. */
        prvSetupTimerInterrupt();

        /* Start the first task. */
        vPortISRStartFirstTask();       

        /* Should not get here! */
        return 0;
}
/*-----------------------------------------------------------*/

void vPortEndScheduler( void )
{
        /* It is unlikely that the ARM port will require this function as there
        is nothing to return to.  */
}
/*-----------------------------------------------------------*/

/*
 * Setup the timer 0 to generate the tick interrupts at the required frequency.
 */
static void prvSetupTimerInterrupt( void )
{
unsigned portLONG ulCompareMatch;

        PCLKSEL0 = (PCLKSEL0 & (~(0x3<<2))) | (0x01 << 2);
        T0TCR  = 2;         /* Stop and reset the timer */
        T0CTCR = 0;         /* Timer mode               */
        
        /* A 1ms tick does not require the use of the timer prescale.  This is
        defaulted to zero but can be used if necessary. */
        T0PR = portPRESCALE_VALUE;

        /* Calculate the match value required for our wanted tick rate. */
        ulCompareMatch = configCPU_CLOCK_HZ / configTICK_RATE_HZ;

        /* Protect against divide by zero.  Using an if() statement still results
        in a warning - hence the #if. */
        #if portPRESCALE_VALUE != 0
        {
                ulCompareMatch /= ( portPRESCALE_VALUE + 1 );
        }
        #endif
        T0MR1 = ulCompareMatch;

        /* Generate tick with timer 0 compare match. */
        T0MCR  = (3 << 3);  /* Reset timer on match and generate interrupt */

        /* Setup the VIC for the timer. */
        VICIntEnable = 0x00000010;
        
        /* The ISR installed depends on whether the preemptive or cooperative
        scheduler is being used. */
        #if configUSE_PREEMPTION == 1
        {
                extern void ( vPreemptiveTick )( void );
                VICVectAddr4 = ( portLONG ) vPreemptiveTick;
        }
        #else
        {
                extern void ( vNonPreemptiveTick )( void );
                VICVectAddr4 = ( portLONG ) vNonPreemptiveTick;
        }
        #endif

        VICVectCntl4 = 1;

        /* Start the timer - interrupts are disabled when this function is called
        so it is okay to do this here. */
        T0TCR = portENABLE_TIMER;
}
/*-----------------------------------------------------------*/