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293 lines
11 KiB
C
293 lines
11 KiB
C
/*
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FreeRTOS V7.1.0 - Copyright (C) 2011 Real Time Engineers Ltd.
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***************************************************************************
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* *
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* FreeRTOS tutorial books are available in pdf and paperback. *
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* Complete, revised, and edited pdf reference manuals are also *
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* available. *
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* *
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* Purchasing FreeRTOS documentation will not only help you, by *
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* ensuring you get running as quickly as possible and with an *
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* in-depth knowledge of how to use FreeRTOS, it will also help *
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* the FreeRTOS project to continue with its mission of providing *
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* professional grade, cross platform, de facto standard solutions *
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* for microcontrollers - completely free of charge! *
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* *
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* >>> See http://www.FreeRTOS.org/Documentation for details. <<< *
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* *
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* Thank you for using FreeRTOS, and 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 modification to the GPL is included to allow you to
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distribute a combined work that includes FreeRTOS without being obliged to
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provide the source code for proprietary components outside of the FreeRTOS
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kernel. FreeRTOS is distributed in the hope that it will be useful, but
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WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
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or 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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* Implementation of functions defined in portable.h for the ARM CM0 port.
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*----------------------------------------------------------*/
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/* Scheduler includes. */
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#include "FreeRTOS.h"
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#include "task.h"
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/* Constants required to manipulate the NVIC. */
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#define portNVIC_SYSTICK_CTRL ( ( volatile unsigned long *) 0xe000e010 )
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#define portNVIC_SYSTICK_LOAD ( ( volatile unsigned long *) 0xe000e014 )
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#define portNVIC_INT_CTRL ( ( volatile unsigned long *) 0xe000ed04 )
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#define portNVIC_SYSPRI2 ( ( volatile unsigned long *) 0xe000ed20 )
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#define portNVIC_SYSTICK_CLK 0x00000004
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#define portNVIC_SYSTICK_INT 0x00000002
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#define portNVIC_SYSTICK_ENABLE 0x00000001
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#define portNVIC_PENDSVSET 0x10000000
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#define portMIN_INTERRUPT_PRIORITY ( 255UL )
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#define portNVIC_PENDSV_PRI ( portMIN_INTERRUPT_PRIORITY << 16UL )
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#define portNVIC_SYSTICK_PRI ( portMIN_INTERRUPT_PRIORITY << 24UL )
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/* Constants required to set up the initial stack. */
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#define portINITIAL_XPSR ( 0x01000000 )
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/* Each task maintains its own interrupt status in the critical nesting
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variable. */
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static unsigned portBASE_TYPE uxCriticalNesting = 0xaaaaaaaa;
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/*
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* Setup the timer to generate the tick interrupts.
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*/
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static void prvSetupTimerInterrupt( void );
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/*
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* Exception handlers.
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*/
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void xPortPendSVHandler( void ) __attribute__ (( naked ));
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void xPortSysTickHandler( void );
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void vPortSVCHandler( void ) __attribute__ (( naked ));
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/*
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* Start first task is a separate function so it can be tested in isolation.
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*/
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static void vPortStartFirstTask( void ) __attribute__ (( naked ));
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/*-----------------------------------------------------------*/
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/*
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* See header file for description.
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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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/* Simulate the stack frame as it would be created by a context switch
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interrupt. */
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pxTopOfStack--; /* Offset added to account for the way the MCU uses the stack on entry/exit of interrupts. */
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*pxTopOfStack = portINITIAL_XPSR; /* xPSR */
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pxTopOfStack--;
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*pxTopOfStack = ( portSTACK_TYPE ) pxCode; /* PC */
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pxTopOfStack -= 6; /* LR, R12, R3..R1 */
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*pxTopOfStack = ( portSTACK_TYPE ) pvParameters; /* R0 */
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pxTopOfStack -= 8; /* R11..R4. */
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return pxTopOfStack;
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}
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/*-----------------------------------------------------------*/
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void vPortSVCHandler( void )
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{
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__asm volatile (
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" ldr r3, pxCurrentTCBConst2 \n" /* Restore the context. */
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" ldr r1, [r3] \n" /* Use pxCurrentTCBConst to get the pxCurrentTCB address. */
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" ldr r0, [r1] \n" /* The first item in pxCurrentTCB is the task top of stack. */
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" add r0, r0, #16 \n" /* Move to the high registers. */
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" ldmia r0!, {r4-r7} \n" /* Pop the high registers. */
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" mov r8, r4 \n"
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" mov r9, r5 \n"
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" mov r10, r6 \n"
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" mov r11, r7 \n"
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" \n"
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" msr psp, r0 \n" /* Remember the new top of stack for the task. */
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" \n"
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" sub r0, r0, #32 \n" /* Go back for the low registers that are not automatically restored. */
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" ldmia r0!, {r4-r7} \n" /* Pop low registers. */
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" mov r1, r14 \n" /* OR R14 with 0x0d. */
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" movs r0, #0x0d \n"
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" orr r1, r0 \n"
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" bx r1 \n"
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" \n"
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" .align 2 \n"
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"pxCurrentTCBConst2: .word pxCurrentTCB \n"
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);
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}
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/*-----------------------------------------------------------*/
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void vPortStartFirstTask( void )
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{
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__asm volatile(
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" movs r0, #0x00 \n" /* Locate the top of stack. */
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" ldr r0, [r0] \n"
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" msr msp, r0 \n" /* Set the msp back to the start of the stack. */
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" cpsie i \n" /* Globally enable interrupts. */
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" svc 0 \n" /* System call to start first task. */
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" nop \n"
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);
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}
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/*-----------------------------------------------------------*/
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/*
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* See header file for description.
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*/
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portBASE_TYPE xPortStartScheduler( void )
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{
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/* Make PendSV, CallSV and SysTick the same priroity as the kernel. */
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*(portNVIC_SYSPRI2) |= portNVIC_PENDSV_PRI;
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*(portNVIC_SYSPRI2) |= portNVIC_SYSTICK_PRI;
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/* Start the timer that generates the tick ISR. Interrupts are disabled
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here already. */
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prvSetupTimerInterrupt();
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/* Initialise the critical nesting count ready for the first task. */
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uxCriticalNesting = 0;
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/* Start the first task. */
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vPortStartFirstTask();
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/* Should not get here! */
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return 0;
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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 CM0 port will require this function as there
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is nothing to return to. */
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}
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/*-----------------------------------------------------------*/
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void vPortYieldFromISR( void )
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{
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/* Set a PendSV to request a context switch. */
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*( portNVIC_INT_CTRL ) = portNVIC_PENDSVSET;
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}
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/*-----------------------------------------------------------*/
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void vPortEnterCritical( void )
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{
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portDISABLE_INTERRUPTS();
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uxCriticalNesting++;
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}
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/*-----------------------------------------------------------*/
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void vPortExitCritical( void )
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{
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uxCriticalNesting--;
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if( uxCriticalNesting == 0 )
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{
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portENABLE_INTERRUPTS();
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}
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}
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/*-----------------------------------------------------------*/
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void xPortPendSVHandler( void )
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{
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/* This is a naked function. */
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__asm volatile
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(
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" mrs r0, psp \n"
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" \n"
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" ldr r3, pxCurrentTCBConst \n" /* Get the location of the current TCB. */
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" ldr r2, [r3] \n"
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" \n"
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" sub r0, r0, #32 \n" /* Make space for the remaining low registers. */
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" str r0, [r2] \n" /* Save the new top of stack. */
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" stmia r0!, {r4-r7} \n" /* Store the low registers that are not saved automatically. */
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" mov r4, r8 \n" /* Store the high registers. */
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" mov r5, r9 \n"
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" mov r6, r10 \n"
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" mov r7, r11 \n"
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" stmia r0!, {r4-r7} \n"
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" \n"
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" push {r3, r14} \n"
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" cpsid i \n"
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" bl vTaskSwitchContext \n"
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" cpsie i \n"
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" pop {r2, r3} \n" /* lr goes in r3. r2 now holds tcb pointer. */
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" \n"
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" ldr r1, [r2] \n"
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" ldr r0, [r1] \n" /* The first item in pxCurrentTCB is the task top of stack. */
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" add r0, r0, #16 \n" /* Move to the high registers. */
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" ldmia r0!, {r4-r7} \n" /* Pop the high registers. */
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" mov r8, r4 \n"
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" mov r9, r5 \n"
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" mov r10, r6 \n"
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" mov r11, r7 \n"
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" \n"
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" msr psp, r0 \n" /* Remember the new top of stack for the task. */
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" \n"
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" sub r0, r0, #32 \n" /* Go back for the low registers that are not automatically restored. */
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" ldmia r0!, {r4-r7} \n" /* Pop low registers. */
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" \n"
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" bx r3 \n"
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" \n"
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" .align 2 \n"
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"pxCurrentTCBConst: .word pxCurrentTCB "
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);
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}
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/*-----------------------------------------------------------*/
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void xPortSysTickHandler( void )
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{
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unsigned long ulDummy;
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/* If using preemption, also force a context switch. */
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#if configUSE_PREEMPTION == 1
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*(portNVIC_INT_CTRL) = portNVIC_PENDSVSET;
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#endif
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ulDummy = portSET_INTERRUPT_MASK_FROM_ISR();
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{
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vTaskIncrementTick();
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}
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portCLEAR_INTERRUPT_MASK_FROM_ISR( ulDummy );
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}
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/*-----------------------------------------------------------*/
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/*
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* Setup the systick timer to generate the tick interrupts at the required
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* frequency.
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*/
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void prvSetupTimerInterrupt( void )
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{
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/* Configure SysTick to interrupt at the requested rate. */
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*(portNVIC_SYSTICK_LOAD) = ( configCPU_CLOCK_HZ / configTICK_RATE_HZ ) - 1UL;
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*(portNVIC_SYSTICK_CTRL) = portNVIC_SYSTICK_CLK | portNVIC_SYSTICK_INT | portNVIC_SYSTICK_ENABLE;
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}
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/*-----------------------------------------------------------*/
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