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Richard Barry 2012-08-11 21:34:11 +00:00
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FreeRTOS/Source/portable/GCC/MSP430F449/port.c Normal file
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/*
FreeRTOS V7.1.1 - Copyright (C) 2012 Real Time Engineers Ltd.
***************************************************************************
* *
* FreeRTOS tutorial books are available in pdf and paperback. *
* Complete, revised, and edited pdf reference manuals are also *
* available. *
* *
* Purchasing FreeRTOS documentation will not only help you, by *
* ensuring you get running as quickly as possible and with an *
* in-depth knowledge of how to use FreeRTOS, it will also help *
* the FreeRTOS project to continue with its mission of providing *
* professional grade, cross platform, de facto standard solutions *
* for microcontrollers - completely free of charge! *
* *
* >>> See http://www.FreeRTOS.org/Documentation for details. <<< *
* *
* Thank you for using FreeRTOS, and 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 modification 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!
***************************************************************************
* *
* Having a problem? Start by reading the FAQ "My application does *
* not run, what could be wrong? *
* *
* http://www.FreeRTOS.org/FAQHelp.html *
* *
***************************************************************************
http://www.FreeRTOS.org - Documentation, training, latest information,
license and contact details.
http://www.FreeRTOS.org/plus - A selection of FreeRTOS ecosystem products,
including FreeRTOS+Trace - an indispensable productivity tool.
Real Time Engineers ltd license FreeRTOS to High Integrity Systems, who sell
the code with commercial support, indemnification, and middleware, under
the OpenRTOS brand: http://www.OpenRTOS.com. High Integrity Systems also
provide a safety engineered and independently SIL3 certified version under
the SafeRTOS brand: http://www.SafeRTOS.com.
*/
/*
Changes from V2.5.2
+ usCriticalNesting now has a volatile qualifier.
*/
/* Standard includes. */
#include <stdlib.h>
#include <signal.h>
/* Scheduler includes. */
#include "FreeRTOS.h"
#include "task.h"
/*-----------------------------------------------------------
* Implementation of functions defined in portable.h for the MSP430 port.
*----------------------------------------------------------*/
/* Constants required for hardware setup. The tick ISR runs off the ACLK,
not the MCLK. */
#define portACLK_FREQUENCY_HZ ( ( portTickType ) 32768 )
#define portINITIAL_CRITICAL_NESTING ( ( unsigned short ) 10 )
#define portFLAGS_INT_ENABLED ( ( portSTACK_TYPE ) 0x08 )
/* 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;
/* Most ports implement critical sections by placing the interrupt flags on
the stack before disabling interrupts. Exiting the critical section is then
simply a case of popping the flags from the stack. As mspgcc does not use
a frame pointer this cannot be done as modifying the stack will clobber all
the stack variables. Instead each task maintains a count of the critical
section nesting depth. Each time a critical section is entered the count is
incremented. Each time a critical section is left the count is decremented -
with interrupts only being re-enabled if the count is zero.
usCriticalNesting will get set to zero when the scheduler starts, but must
not be initialised to zero as this will cause problems during the startup
sequence. */
volatile unsigned short usCriticalNesting = portINITIAL_CRITICAL_NESTING;
/*-----------------------------------------------------------*/
/*
* Macro to save a task context to the task stack. This simply pushes all the
* general purpose msp430 registers onto the stack, followed by the
* usCriticalNesting value used by the task. Finally the resultant stack
* pointer value is saved into the task control block so it can be retrieved
* the next time the task executes.
*/
#define portSAVE_CONTEXT() \
asm volatile ( "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" \
"mov.w usCriticalNesting, r14 \n\t" \
"push r14 \n\t" \
"mov.w pxCurrentTCB, r12 \n\t" \
"mov.w r1, @r12 \n\t" \
);
/*
* Macro to restore a task context from the task stack. This is effectively
* the reverse of portSAVE_CONTEXT(). First the stack pointer value is
* loaded from the task control block. Next the value for usCriticalNesting
* used by the task is retrieved from the stack - followed by the value of all
* the general purpose msp430 registers.
*
* The bic instruction ensures there are no low power bits set in the status
* register that is about to be popped from the stack.
*/
#define portRESTORE_CONTEXT() \
asm volatile ( "mov.w pxCurrentTCB, r12 \n\t" \
"mov.w @r12, r1 \n\t" \
"pop r15 \n\t" \
"mov.w r15, usCriticalNesting \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" \
"bic #(0xf0),0(r1) \n\t" \
"reti \n\t" \
);
/*-----------------------------------------------------------*/
/*
* Sets up the periodic ISR used for the RTOS tick. This uses timer 0, but
* could have alternatively used the watchdog timer or timer 1.
*/
static void prvSetupTimerInterrupt( void );
/*-----------------------------------------------------------*/
/*
* Initialise the stack of a task to look exactly as if a call to
* portSAVE_CONTEXT had been called.
*
* See the header file portable.h.
*/
portSTACK_TYPE *pxPortInitialiseStack( portSTACK_TYPE *pxTopOfStack, pdTASK_CODE pxCode, void *pvParameters )
{
/*
Place a few bytes of known values on the bottom of the stack.
This is just useful for debugging and can be included if required.
*pxTopOfStack = ( portSTACK_TYPE ) 0x1111;
pxTopOfStack--;
*pxTopOfStack = ( portSTACK_TYPE ) 0x2222;
pxTopOfStack--;
*pxTopOfStack = ( portSTACK_TYPE ) 0x3333;
pxTopOfStack--;
*/
/* The msp430 automatically pushes the PC then SR onto the stack before
executing an ISR. We want the stack to look just as if this has happened
so place a pointer to the start of the task on the stack first - followed
by the flags we want the task to use when it starts up. */
*pxTopOfStack = ( portSTACK_TYPE ) pxCode;
pxTopOfStack--;
*pxTopOfStack = portFLAGS_INT_ENABLED;
pxTopOfStack--;
/* Next the general purpose registers. */
*pxTopOfStack = ( portSTACK_TYPE ) 0x4444;
pxTopOfStack--;
*pxTopOfStack = ( portSTACK_TYPE ) 0x5555;
pxTopOfStack--;
*pxTopOfStack = ( portSTACK_TYPE ) 0x6666;
pxTopOfStack--;
*pxTopOfStack = ( portSTACK_TYPE ) 0x7777;
pxTopOfStack--;
*pxTopOfStack = ( portSTACK_TYPE ) 0x8888;
pxTopOfStack--;
*pxTopOfStack = ( portSTACK_TYPE ) 0x9999;
pxTopOfStack--;
*pxTopOfStack = ( portSTACK_TYPE ) 0xaaaa;
pxTopOfStack--;
*pxTopOfStack = ( portSTACK_TYPE ) 0xbbbb;
pxTopOfStack--;
*pxTopOfStack = ( portSTACK_TYPE ) 0xcccc;
pxTopOfStack--;
*pxTopOfStack = ( portSTACK_TYPE ) 0xdddd;
pxTopOfStack--;
*pxTopOfStack = ( portSTACK_TYPE ) 0xeeee;
pxTopOfStack--;
/* When the task starts is will expect to find the function parameter in
R15. */
*pxTopOfStack = ( portSTACK_TYPE ) pvParameters;
pxTopOfStack--;
/* The code generated by the mspgcc compiler does not maintain separate
stack and frame pointers. The portENTER_CRITICAL macro cannot therefore
use the stack as per other ports. Instead a variable is used to keep
track of the critical section nesting. This variable has to be stored
as part of the task context and is initially set to zero. */
*pxTopOfStack = ( portSTACK_TYPE ) portNO_CRITICAL_SECTION_NESTING;
/* Return a pointer to the top of the stack we have generated so this can
be stored in the task control block for the task. */
return pxTopOfStack;
}
/*-----------------------------------------------------------*/
portBASE_TYPE xPortStartScheduler( void )
{
/* Setup the hardware to generate the tick. Interrupts are disabled when
this function is called. */
prvSetupTimerInterrupt();
/* Restore the context of the first task that is going to run. */
portRESTORE_CONTEXT();
/* Should not get here as the tasks are now running! */
return pdTRUE;
}
/*-----------------------------------------------------------*/
void vPortEndScheduler( void )
{
/* It is unlikely that the MSP430 port will get stopped. If required simply
disable the tick interrupt here. */
}
/*-----------------------------------------------------------*/
/*
* Manual context switch called by portYIELD or taskYIELD.
*
* The first thing we do is save the registers so we can use a naked attribute.
*/
void vPortYield( void ) __attribute__ ( ( naked ) );
void vPortYield( void )
{
/* We want the stack of the task being saved to look exactly as if the task
was saved during a pre-emptive RTOS tick ISR. Before calling an ISR the
msp430 places the status register onto the stack. As this is a function
call and not an ISR we have to do this manually. */
asm volatile ( "push r2" );
_DINT();
/* Save the context of the current task. */
portSAVE_CONTEXT();
/* Switch to the highest priority task that is ready to run. */
vTaskSwitchContext();
/* Restore the context of the new task. */
portRESTORE_CONTEXT();
}
/*-----------------------------------------------------------*/
/*
* Hardware initialisation to generate the RTOS tick. This uses timer 0
* but could alternatively use the watchdog timer or timer 1.
*/
static void prvSetupTimerInterrupt( void )
{
/* Ensure the timer is stopped. */
TACTL = 0;
/* Run the timer of the ACLK. */
TACTL = TASSEL_1;
/* Clear everything to start with. */
TACTL |= TACLR;
/* Set the compare match value according to the tick rate we want. */
TACCR0 = portACLK_FREQUENCY_HZ / configTICK_RATE_HZ;
/* Enable the interrupts. */
TACCTL0 = CCIE;
/* Start up clean. */
TACTL |= TACLR;
/* Up mode. */
TACTL |= MC_1;
}
/*-----------------------------------------------------------*/
/*
* The interrupt service routine used depends on whether the pre-emptive
* scheduler is being used or not.
*/
#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.
*/
interrupt (TIMERA0_VECTOR) prvTickISR( void ) __attribute__ ( ( naked ) );
interrupt (TIMERA0_VECTOR) prvTickISR( void )
{
/* Save the context of the interrupted task. */
portSAVE_CONTEXT();
/* Increment the tick count then switch to the highest priority task
that is ready to run. */
vTaskIncrementTick();
vTaskSwitchContext();
/* Restore the context of the new task. */
portRESTORE_CONTEXT();
}
#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();
*/
interrupt (TIMERA0_VECTOR) prvTickISR( void );
interrupt (TIMERA0_VECTOR) prvTickISR( void )
{
vTaskIncrementTick();
}
#endif