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jeremybenn |
/*
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FreeRTOS V6.1.1 - Copyright (C) 2011 Real Time Engineers Ltd.
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***************************************************************************
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* *
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* If you are: *
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* *
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* + New to FreeRTOS, *
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* + Wanting to learn FreeRTOS or multitasking in general quickly *
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* + Looking for basic training, *
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* + Wanting to improve your FreeRTOS skills and productivity *
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* *
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* then take a look at the FreeRTOS books - available as PDF or paperback *
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* *
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* "Using the FreeRTOS Real Time Kernel - a Practical Guide" *
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* http://www.FreeRTOS.org/Documentation *
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* *
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* A pdf reference manual is also available. Both are usually delivered *
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* to your inbox within 20 minutes to two hours when purchased between 8am *
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* and 8pm GMT (although please allow up to 24 hours in case of *
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* exceptional circumstances). Thank you for your support! *
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* *
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***************************************************************************
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This file is part of the FreeRTOS distribution.
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FreeRTOS is free software; you can redistribute it and/or modify it under
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the terms of the GNU General Public License (version 2) as published by the
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Free Software Foundation AND MODIFIED BY the FreeRTOS exception.
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***NOTE*** The exception to the GPL is included to allow you to distribute
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a combined work that includes FreeRTOS without being obliged to provide the
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source code for proprietary components outside of the FreeRTOS kernel.
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FreeRTOS is distributed in the hope that it will be useful, but WITHOUT
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ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
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more details. You should have received a copy of the GNU General Public
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License and the FreeRTOS license exception along with FreeRTOS; if not it
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can be viewed here: http://www.freertos.org/a00114.html and also obtained
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by writing to Richard Barry, contact details for whom are available on the
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FreeRTOS WEB site.
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1 tab == 4 spaces!
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http://www.FreeRTOS.org - Documentation, latest information, license and
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contact details.
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http://www.SafeRTOS.com - A version that is certified for use in safety
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critical systems.
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http://www.OpenRTOS.com - Commercial support, development, porting,
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licensing and training services.
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*/
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/*
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Changes from V2.5.2
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+ usCriticalNesting now has a volatile qualifier.
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*/
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/* Standard includes. */
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#include <stdlib.h>
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#include <signal.h>
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/* Scheduler includes. */
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#include "FreeRTOS.h"
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#include "task.h"
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/*-----------------------------------------------------------
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* Implementation of functions defined in portable.h for the MSP430 port.
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*----------------------------------------------------------*/
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/* Constants required for hardware setup. The tick ISR runs off the ACLK,
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not the MCLK. */
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#define portACLK_FREQUENCY_HZ ( ( portTickType ) 32768 )
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#define portINITIAL_CRITICAL_NESTING ( ( unsigned short ) 10 )
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#define portFLAGS_INT_ENABLED ( ( portSTACK_TYPE ) 0x08 )
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/* We require the address of the pxCurrentTCB variable, but don't want to know
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any details of its type. */
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typedef void tskTCB;
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extern volatile tskTCB * volatile pxCurrentTCB;
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/* Most ports implement critical sections by placing the interrupt flags on
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the stack before disabling interrupts. Exiting the critical section is then
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simply a case of popping the flags from the stack. As mspgcc does not use
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a frame pointer this cannot be done as modifying the stack will clobber all
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the stack variables. Instead each task maintains a count of the critical
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section nesting depth. Each time a critical section is entered the count is
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incremented. Each time a critical section is left the count is decremented -
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with interrupts only being re-enabled if the count is zero.
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usCriticalNesting will get set to zero when the scheduler starts, but must
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not be initialised to zero as this will cause problems during the startup
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sequence. */
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volatile unsigned short usCriticalNesting = portINITIAL_CRITICAL_NESTING;
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/*-----------------------------------------------------------*/
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/*
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* Macro to save a task context to the task stack. This simply pushes all the
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* general purpose msp430 registers onto the stack, followed by the
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* usCriticalNesting value used by the task. Finally the resultant stack
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* pointer value is saved into the task control block so it can be retrieved
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* the next time the task executes.
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*/
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#define portSAVE_CONTEXT() \
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asm volatile ( "push r4 \n\t" \
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"push r5 \n\t" \
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"push r6 \n\t" \
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"push r7 \n\t" \
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"push r8 \n\t" \
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"push r9 \n\t" \
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"push r10 \n\t" \
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"push r11 \n\t" \
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"push r12 \n\t" \
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"push r13 \n\t" \
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"push r14 \n\t" \
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"push r15 \n\t" \
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"mov.w usCriticalNesting, r14 \n\t" \
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"push r14 \n\t" \
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"mov.w pxCurrentTCB, r12 \n\t" \
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"mov.w r1, @r12 \n\t" \
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);
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/*
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* Macro to restore a task context from the task stack. This is effectively
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* the reverse of portSAVE_CONTEXT(). First the stack pointer value is
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* loaded from the task control block. Next the value for usCriticalNesting
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* used by the task is retrieved from the stack - followed by the value of all
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* the general purpose msp430 registers.
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*
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* The bic instruction ensures there are no low power bits set in the status
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* register that is about to be popped from the stack.
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*/
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#define portRESTORE_CONTEXT() \
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asm volatile ( "mov.w pxCurrentTCB, r12 \n\t" \
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"mov.w @r12, r1 \n\t" \
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"pop r15 \n\t" \
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"mov.w r15, usCriticalNesting \n\t" \
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"pop r15 \n\t" \
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"pop r14 \n\t" \
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"pop r13 \n\t" \
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"pop r12 \n\t" \
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"pop r11 \n\t" \
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"pop r10 \n\t" \
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"pop r9 \n\t" \
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"pop r8 \n\t" \
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"pop r7 \n\t" \
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"pop r6 \n\t" \
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"pop r5 \n\t" \
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"pop r4 \n\t" \
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"bic #(0xf0),0(r1) \n\t" \
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"reti \n\t" \
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);
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/*-----------------------------------------------------------*/
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/*
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* Sets up the periodic ISR used for the RTOS tick. This uses timer 0, but
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* could have alternatively used the watchdog timer or timer 1.
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*/
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static void prvSetupTimerInterrupt( void );
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/*-----------------------------------------------------------*/
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/*
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* Initialise the stack of a task to look exactly as if a call to
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* portSAVE_CONTEXT had been called.
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*
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* See the header file portable.h.
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*/
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portSTACK_TYPE *pxPortInitialiseStack( portSTACK_TYPE *pxTopOfStack, pdTASK_CODE pxCode, void *pvParameters )
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{
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/*
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Place a few bytes of known values on the bottom of the stack.
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This is just useful for debugging and can be included if required.
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*pxTopOfStack = ( portSTACK_TYPE ) 0x1111;
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pxTopOfStack--;
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*pxTopOfStack = ( portSTACK_TYPE ) 0x2222;
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pxTopOfStack--;
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*pxTopOfStack = ( portSTACK_TYPE ) 0x3333;
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pxTopOfStack--;
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*/
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/* The msp430 automatically pushes the PC then SR onto the stack before
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executing an ISR. We want the stack to look just as if this has happened
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so place a pointer to the start of the task on the stack first - followed
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by the flags we want the task to use when it starts up. */
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*pxTopOfStack = ( portSTACK_TYPE ) pxCode;
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pxTopOfStack--;
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*pxTopOfStack = portFLAGS_INT_ENABLED;
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pxTopOfStack--;
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/* Next the general purpose registers. */
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*pxTopOfStack = ( portSTACK_TYPE ) 0x4444;
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pxTopOfStack--;
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*pxTopOfStack = ( portSTACK_TYPE ) 0x5555;
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pxTopOfStack--;
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*pxTopOfStack = ( portSTACK_TYPE ) 0x6666;
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pxTopOfStack--;
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*pxTopOfStack = ( portSTACK_TYPE ) 0x7777;
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pxTopOfStack--;
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*pxTopOfStack = ( portSTACK_TYPE ) 0x8888;
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pxTopOfStack--;
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*pxTopOfStack = ( portSTACK_TYPE ) 0x9999;
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pxTopOfStack--;
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*pxTopOfStack = ( portSTACK_TYPE ) 0xaaaa;
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pxTopOfStack--;
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*pxTopOfStack = ( portSTACK_TYPE ) 0xbbbb;
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pxTopOfStack--;
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*pxTopOfStack = ( portSTACK_TYPE ) 0xcccc;
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pxTopOfStack--;
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*pxTopOfStack = ( portSTACK_TYPE ) 0xdddd;
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pxTopOfStack--;
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*pxTopOfStack = ( portSTACK_TYPE ) 0xeeee;
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pxTopOfStack--;
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/* When the task starts is will expect to find the function parameter in
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R15. */
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*pxTopOfStack = ( portSTACK_TYPE ) pvParameters;
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pxTopOfStack--;
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/* The code generated by the mspgcc compiler does not maintain separate
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stack and frame pointers. The portENTER_CRITICAL macro cannot therefore
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use the stack as per other ports. Instead a variable is used to keep
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track of the critical section nesting. This variable has to be stored
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as part of the task context and is initially set to zero. */
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*pxTopOfStack = ( portSTACK_TYPE ) portNO_CRITICAL_SECTION_NESTING;
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/* Return a pointer to the top of the stack we have generated so this can
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be stored in the task control block for the task. */
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return pxTopOfStack;
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}
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/*-----------------------------------------------------------*/
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portBASE_TYPE xPortStartScheduler( void )
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{
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/* Setup the hardware to generate the tick. Interrupts are disabled when
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this function is called. */
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prvSetupTimerInterrupt();
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/* Restore the context of the first task that is going to run. */
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portRESTORE_CONTEXT();
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/* Should not get here as the tasks are now running! */
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return pdTRUE;
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}
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/*-----------------------------------------------------------*/
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void vPortEndScheduler( void )
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{
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/* It is unlikely that the MSP430 port will get stopped. If required simply
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disable the tick interrupt here. */
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}
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/*-----------------------------------------------------------*/
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/*
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* Manual context switch called by portYIELD or taskYIELD.
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*
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* The first thing we do is save the registers so we can use a naked attribute.
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*/
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void vPortYield( void ) __attribute__ ( ( naked ) );
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void vPortYield( void )
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{
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/* We want the stack of the task being saved to look exactly as if the task
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was saved during a pre-emptive RTOS tick ISR. Before calling an ISR the
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msp430 places the status register onto the stack. As this is a function
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call and not an ISR we have to do this manually. */
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asm volatile ( "push r2" );
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_DINT();
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/* Save the context of the current task. */
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portSAVE_CONTEXT();
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/* Switch to the highest priority task that is ready to run. */
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vTaskSwitchContext();
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/* Restore the context of the new task. */
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portRESTORE_CONTEXT();
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}
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/*-----------------------------------------------------------*/
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/*
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* Hardware initialisation to generate the RTOS tick. This uses timer 0
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* but could alternatively use the watchdog timer or timer 1.
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*/
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static void prvSetupTimerInterrupt( void )
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{
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| 287 |
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/* Ensure the timer is stopped. */
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TACTL = 0;
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/* Run the timer of the ACLK. */
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TACTL = TASSEL_1;
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/* Clear everything to start with. */
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TACTL |= TACLR;
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| 296 |
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/* Set the compare match value according to the tick rate we want. */
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TACCR0 = portACLK_FREQUENCY_HZ / configTICK_RATE_HZ;
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| 299 |
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/* Enable the interrupts. */
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TACCTL0 = CCIE;
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/* Start up clean. */
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TACTL |= TACLR;
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/* Up mode. */
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TACTL |= MC_1;
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}
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/*-----------------------------------------------------------*/
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/*
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* The interrupt service routine used depends on whether the pre-emptive
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* scheduler is being used or not.
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| 313 |
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*/
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| 315 |
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#if configUSE_PREEMPTION == 1
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| 316 |
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| 317 |
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/*
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| 318 |
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* Tick ISR for preemptive scheduler. We can use a naked attribute as
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| 319 |
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* the context is saved at the start of vPortYieldFromTick(). The tick
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| 320 |
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* count is incremented after the context is saved.
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*/
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| 322 |
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interrupt (TIMERA0_VECTOR) prvTickISR( void ) __attribute__ ( ( naked ) );
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| 323 |
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interrupt (TIMERA0_VECTOR) prvTickISR( void )
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| 324 |
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{
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| 325 |
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/* Save the context of the interrupted task. */
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| 326 |
|
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portSAVE_CONTEXT();
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| 327 |
|
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| 328 |
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/* Increment the tick count then switch to the highest priority task
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| 329 |
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that is ready to run. */
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| 330 |
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vTaskIncrementTick();
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| 331 |
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vTaskSwitchContext();
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| 332 |
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| 333 |
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/* Restore the context of the new task. */
|
| 334 |
|
|
portRESTORE_CONTEXT();
|
| 335 |
|
|
}
|
| 336 |
|
|
|
| 337 |
|
|
#else
|
| 338 |
|
|
|
| 339 |
|
|
/*
|
| 340 |
|
|
* Tick ISR for the cooperative scheduler. All this does is increment the
|
| 341 |
|
|
* tick count. We don't need to switch context, this can only be done by
|
| 342 |
|
|
* manual calls to taskYIELD();
|
| 343 |
|
|
*/
|
| 344 |
|
|
interrupt (TIMERA0_VECTOR) prvTickISR( void );
|
| 345 |
|
|
interrupt (TIMERA0_VECTOR) prvTickISR( void )
|
| 346 |
|
|
{
|
| 347 |
|
|
vTaskIncrementTick();
|
| 348 |
|
|
}
|
| 349 |
|
|
#endif
|
| 350 |
|
|
|
| 351 |
|
|
|
| 352 |
|
|
|
