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/*
FreeRTOS V7.5.2 - Copyright (C) 2013 Real Time Engineers Ltd.
VISIT http://www.FreeRTOS.org TO ENSURE YOU ARE USING THE LATEST VERSION.
***************************************************************************
* *
* FreeRTOS provides completely free yet professionally developed, *
* robust, strictly quality controlled, supported, and cross *
* platform software that has become a de facto standard. *
* *
* Help yourself get started quickly and support the FreeRTOS *
* project by purchasing a FreeRTOS tutorial book, reference *
* manual, or both from: http://www.FreeRTOS.org/Documentation *
* *
* Thank you! *
* *
***************************************************************************
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. Full license text is available from the following
link: http://www.freertos.org/a00114.html
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, books, training, latest versions,
license and Real Time Engineers Ltd. contact details.
http://www.FreeRTOS.org/plus - A selection of FreeRTOS ecosystem products,
including FreeRTOS+Trace - an indispensable productivity tool, a DOS
compatible FAT file system, and our tiny thread aware UDP/IP stack.
http://www.OpenRTOS.com - Real Time Engineers ltd license FreeRTOS to High
Integrity Systems to sell under the OpenRTOS brand. Low cost OpenRTOS
licenses offer ticketed support, indemnification and middleware.
http://www.SafeRTOS.com - High Integrity Systems also provide a safety
engineered and independently SIL3 certified version for use in safety and
mission critical applications that require provable dependability.
1 tab == 4 spaces!
*/
/*-----------------------------------------------------------
* Implementation of functions defined in portable.h for the ARM CM0 port.
*----------------------------------------------------------*/
/* Scheduler includes. */
#include "FreeRTOS.h"
#include "task.h"
/* Constants required to manipulate the NVIC. */
#define portNVIC_SYSTICK_CTRL ( ( volatile unsigned long *) 0xe000e010 )
#define portNVIC_SYSTICK_LOAD ( ( volatile unsigned long *) 0xe000e014 )
#define portNVIC_INT_CTRL ( ( volatile unsigned long *) 0xe000ed04 )
#define portNVIC_SYSPRI2 ( ( volatile unsigned long *) 0xe000ed20 )
#define portNVIC_SYSTICK_CLK 0x00000004
#define portNVIC_SYSTICK_INT 0x00000002
#define portNVIC_SYSTICK_ENABLE 0x00000001
#define portNVIC_PENDSVSET 0x10000000
#define portMIN_INTERRUPT_PRIORITY ( 255UL )
#define portNVIC_PENDSV_PRI ( portMIN_INTERRUPT_PRIORITY << 16UL )
#define portNVIC_SYSTICK_PRI ( portMIN_INTERRUPT_PRIORITY << 24UL )
/* Constants required to set up the initial stack. */
#define portINITIAL_XPSR ( 0x01000000 )
/* Each task maintains its own interrupt status in the critical nesting
variable. */
static unsigned portBASE_TYPE uxCriticalNesting = 0xaaaaaaaa;
/*
* Setup the timer to generate the tick interrupts.
*/
static void prvSetupTimerInterrupt( void );
/*
* Exception handlers.
*/
void xPortPendSVHandler( void ) __attribute__ (( naked ));
void xPortSysTickHandler( void );
void vPortSVCHandler( void ) __attribute__ (( naked ));
/*
* Start first task is a separate function so it can be tested in isolation.
*/
static void vPortStartFirstTask( void ) __attribute__ (( naked ));
/*-----------------------------------------------------------*/
/*
* See header file for description.
*/
portSTACK_TYPE *pxPortInitialiseStack( portSTACK_TYPE *pxTopOfStack, pdTASK_CODE pxCode, void *pvParameters )
{
/* Simulate the stack frame as it would be created by a context switch
interrupt. */
pxTopOfStack--; /* Offset added to account for the way the MCU uses the stack on entry/exit of interrupts. */
*pxTopOfStack = portINITIAL_XPSR; /* xPSR */
pxTopOfStack--;
*pxTopOfStack = ( portSTACK_TYPE ) pxCode; /* PC */
pxTopOfStack -= 6; /* LR, R12, R3..R1 */
*pxTopOfStack = ( portSTACK_TYPE ) pvParameters; /* R0 */
pxTopOfStack -= 8; /* R11..R4. */
return pxTopOfStack;
}
/*-----------------------------------------------------------*/
void vPortSVCHandler( void )
{
__asm volatile (
" ldr r3, pxCurrentTCBConst2 \n" /* Restore the context. */
" ldr r1, [r3] \n" /* Use pxCurrentTCBConst to get the pxCurrentTCB address. */
" ldr r0, [r1] \n" /* The first item in pxCurrentTCB is the task top of stack. */
" add r0, r0, #16 \n" /* Move to the high registers. */
" ldmia r0!, {r4-r7} \n" /* Pop the high registers. */
" mov r8, r4 \n"
" mov r9, r5 \n"
" mov r10, r6 \n"
" mov r11, r7 \n"
" \n"
" msr psp, r0 \n" /* Remember the new top of stack for the task. */
" \n"
" sub r0, r0, #32 \n" /* Go back for the low registers that are not automatically restored. */
" ldmia r0!, {r4-r7} \n" /* Pop low registers. */
" mov r1, r14 \n" /* OR R14 with 0x0d. */
" movs r0, #0x0d \n"
" orr r1, r0 \n"
" bx r1 \n"
" \n"
" .align 2 \n"
"pxCurrentTCBConst2: .word pxCurrentTCB \n"
);
}
/*-----------------------------------------------------------*/
void vPortStartFirstTask( void )
{
/* The MSP stack is not reset as, unlike on M3/4 parts, there is no vector
table offset register that can be used to locate the initial stack value.
Not all M0 parts have the application vector table at address 0. */
__asm volatile(
" cpsie i \n" /* Globally enable interrupts. */
" svc 0 \n" /* System call to start first task. */
" nop \n"
);
}
/*-----------------------------------------------------------*/
/*
* See header file for description.
*/
portBASE_TYPE xPortStartScheduler( void )
{
/* Make PendSV, CallSV and SysTick the same priroity as the kernel. */
*(portNVIC_SYSPRI2) |= portNVIC_PENDSV_PRI;
*(portNVIC_SYSPRI2) |= portNVIC_SYSTICK_PRI;
/* Start the timer that generates the tick ISR. Interrupts are disabled
here already. */
prvSetupTimerInterrupt();
/* Initialise the critical nesting count ready for the first task. */
uxCriticalNesting = 0;
/* Start the first task. */
vPortStartFirstTask();
/* Should not get here! */
return 0;
}
/*-----------------------------------------------------------*/
void vPortEndScheduler( void )
{
/* It is unlikely that the CM0 port will require this function as there
is nothing to return to. */
}
/*-----------------------------------------------------------*/
void vPortYield( void )
{
/* Set a PendSV to request a context switch. */
*( portNVIC_INT_CTRL ) = portNVIC_PENDSVSET;
/* Barriers are normally not required but do ensure the code is completely
within the specified behaviour for the architecture. */
__asm volatile( "dsb" );
__asm volatile( "isb" );
}
/*-----------------------------------------------------------*/
void vPortEnterCritical( void )
{
portDISABLE_INTERRUPTS();
uxCriticalNesting++;
__asm volatile( "dsb" );
__asm volatile( "isb" );
}
/*-----------------------------------------------------------*/
void vPortExitCritical( void )
{
uxCriticalNesting--;
if( uxCriticalNesting == 0 )
{
portENABLE_INTERRUPTS();
}
}
/*-----------------------------------------------------------*/
unsigned long ulSetInterruptMaskFromISR( void )
{
__asm volatile(
" mrs r0, PRIMASK \n"
" cpsid i \n"
" bx lr "
);
/* To avoid compiler warnings. This line will never be reached. */
return 0;
}
/*-----------------------------------------------------------*/
void vClearInterruptMaskFromISR( unsigned long ulMask )
{
__asm volatile(
" msr PRIMASK, r0 \n"
" bx lr "
);
}
/*-----------------------------------------------------------*/
void xPortPendSVHandler( void )
{
/* This is a naked function. */
__asm volatile
(
" mrs r0, psp \n"
" \n"
" ldr r3, pxCurrentTCBConst \n" /* Get the location of the current TCB. */
" ldr r2, [r3] \n"
" \n"
" sub r0, r0, #32 \n" /* Make space for the remaining low registers. */
" str r0, [r2] \n" /* Save the new top of stack. */
" stmia r0!, {r4-r7} \n" /* Store the low registers that are not saved automatically. */
" mov r4, r8 \n" /* Store the high registers. */
" mov r5, r9 \n"
" mov r6, r10 \n"
" mov r7, r11 \n"
" stmia r0!, {r4-r7} \n"
" \n"
" push {r3, r14} \n"
" cpsid i \n"
" bl vTaskSwitchContext \n"
" cpsie i \n"
" pop {r2, r3} \n" /* lr goes in r3. r2 now holds tcb pointer. */
" \n"
" ldr r1, [r2] \n"
" ldr r0, [r1] \n" /* The first item in pxCurrentTCB is the task top of stack. */
" add r0, r0, #16 \n" /* Move to the high registers. */
" ldmia r0!, {r4-r7} \n" /* Pop the high registers. */
" mov r8, r4 \n"
" mov r9, r5 \n"
" mov r10, r6 \n"
" mov r11, r7 \n"
" \n"
" msr psp, r0 \n" /* Remember the new top of stack for the task. */
" \n"
" sub r0, r0, #32 \n" /* Go back for the low registers that are not automatically restored. */
" ldmia r0!, {r4-r7} \n" /* Pop low registers. */
" \n"
" bx r3 \n"
" \n"
" .align 2 \n"
"pxCurrentTCBConst: .word pxCurrentTCB "
);
}
/*-----------------------------------------------------------*/
void xPortSysTickHandler( void )
{
unsigned long ulPreviousMask;
ulPreviousMask = portSET_INTERRUPT_MASK_FROM_ISR();
{
/* Increment the RTOS tick. */
if( xTaskIncrementTick() != pdFALSE )
{
/* Pend a context switch. */
*(portNVIC_INT_CTRL) = portNVIC_PENDSVSET;
}
}
portCLEAR_INTERRUPT_MASK_FROM_ISR( ulPreviousMask );
}
/*-----------------------------------------------------------*/
/*
* Setup the systick timer to generate the tick interrupts at the required
* frequency.
*/
void prvSetupTimerInterrupt( void )
{
/* Configure SysTick to interrupt at the requested rate. */
*(portNVIC_SYSTICK_LOAD) = ( configCPU_CLOCK_HZ / configTICK_RATE_HZ ) - 1UL;
*(portNVIC_SYSTICK_CTRL) = portNVIC_SYSTICK_CLK | portNVIC_SYSTICK_INT | portNVIC_SYSTICK_ENABLE;
}
/*-----------------------------------------------------------*/
|
