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444 lines
18 KiB
C
444 lines
18 KiB
C
/*
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* FreeRTOS Kernel <DEVELOPMENT BRANCH>
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* Copyright (C) 2021 Amazon.com, Inc. or its affiliates. All Rights Reserved.
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*
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* SPDX-License-Identifier: MIT
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*
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* Permission is hereby granted, free of charge, to any person obtaining a copy of
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* this software and associated documentation files (the "Software"), to deal in
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* the Software without restriction, including without limitation the rights to
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* use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of
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* the Software, and to permit persons to whom the Software is furnished to do so,
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* subject to the following conditions:
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*
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* The above copyright notice and this permission notice shall be included in all
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* copies or substantial portions of the Software.
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*
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* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS
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* FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR
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* COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER
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* IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
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* CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
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*
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* https://www.FreeRTOS.org
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* https://github.com/FreeRTOS
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*
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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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/* IAR includes. */
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#include "intrinsics.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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#ifndef configSYSTICK_CLOCK_HZ
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#define configSYSTICK_CLOCK_HZ configCPU_CLOCK_HZ
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/* Ensure the SysTick is clocked at the same frequency as the core. */
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#define portNVIC_SYSTICK_CLK_BIT ( 1UL << 2UL )
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#else
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/* The way the SysTick is clocked is not modified in case it is not the same
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* as the core. */
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#define portNVIC_SYSTICK_CLK_BIT ( 0 )
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#endif
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/* Constants required to manipulate the NVIC. */
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#define portNVIC_SYSTICK_CTRL_REG ( *( ( volatile uint32_t * ) 0xe000e010 ) )
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#define portNVIC_SYSTICK_LOAD_REG ( *( ( volatile uint32_t * ) 0xe000e014 ) )
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#define portNVIC_SYSTICK_CURRENT_VALUE_REG ( *( ( volatile uint32_t * ) 0xe000e018 ) )
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#define portNVIC_INT_CTRL_REG ( *( ( volatile uint32_t * ) 0xe000ed04 ) )
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#define portNVIC_SHPR3_REG ( *( ( volatile uint32_t * ) 0xe000ed20 ) )
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#define portNVIC_SYSTICK_INT_BIT ( 1UL << 1UL )
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#define portNVIC_SYSTICK_ENABLE_BIT ( 1UL << 0UL )
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#define portNVIC_SYSTICK_COUNT_FLAG_BIT ( 1UL << 16UL )
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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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/* For backward compatibility, ensure configKERNEL_INTERRUPT_PRIORITY is
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* defined. The value 255 should also ensure backward compatibility.
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* FreeRTOS.org versions prior to V4.3.0 did not include this definition. */
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#ifndef configKERNEL_INTERRUPT_PRIORITY
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#define configKERNEL_INTERRUPT_PRIORITY 0
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#endif
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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 UBaseType_t uxCriticalNesting = 0xaaaaaaaa;
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/* The systick is a 24-bit counter. */
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#define portMAX_24_BIT_NUMBER ( 0xffffffUL )
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/* A fiddle factor to estimate the number of SysTick counts that would have
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* occurred while the SysTick counter is stopped during tickless idle
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* calculations. */
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#ifndef portMISSED_COUNTS_FACTOR
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#define portMISSED_COUNTS_FACTOR ( 45UL )
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#endif
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/* The number of SysTick increments that make up one tick period. */
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#if ( configUSE_TICKLESS_IDLE == 1 )
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static uint32_t ulTimerCountsForOneTick = 0;
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#endif /* configUSE_TICKLESS_IDLE */
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/* The maximum number of tick periods that can be suppressed is limited by the
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* 24 bit resolution of the SysTick timer. */
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#if ( configUSE_TICKLESS_IDLE == 1 )
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static uint32_t xMaximumPossibleSuppressedTicks = 0;
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#endif /* configUSE_TICKLESS_IDLE */
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/* Compensate for the CPU cycles that pass while the SysTick is stopped (low
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* power functionality only. */
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#if ( configUSE_TICKLESS_IDLE == 1 )
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static uint32_t ulStoppedTimerCompensation = 0;
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#endif /* configUSE_TICKLESS_IDLE */
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/*
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* Setup the timer to generate the tick interrupts. The implementation in this
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* file is weak to allow application writers to change the timer used to
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* generate the tick interrupt.
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*/
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void vPortSetupTimerInterrupt( void );
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/*
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* Exception handlers.
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*/
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void xPortSysTickHandler( void );
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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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extern void vPortStartFirstTask( void );
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/*
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* Used to catch tasks that attempt to return from their implementing function.
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*/
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static void prvTaskExitError( void );
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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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StackType_t * pxPortInitialiseStack( StackType_t * pxTopOfStack,
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TaskFunction_t pxCode,
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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 = ( StackType_t ) pxCode; /* PC */
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pxTopOfStack--;
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*pxTopOfStack = ( StackType_t ) prvTaskExitError; /* LR */
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pxTopOfStack -= 5; /* R12, R3, R2 and R1. */
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*pxTopOfStack = ( StackType_t ) 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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static void prvTaskExitError( void )
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{
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/* A function that implements a task must not exit or attempt to return to
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* its caller as there is nothing to return to. If a task wants to exit it
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* should instead call vTaskDelete( NULL ).
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*
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* Artificially force an assert() to be triggered if configASSERT() is
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* defined, then stop here so application writers can catch the error. */
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configASSERT( uxCriticalNesting == ~0UL );
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portDISABLE_INTERRUPTS();
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for( ; ; )
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{
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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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BaseType_t xPortStartScheduler( void )
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{
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/* Make PendSV and SysTick the lowest priority interrupts. */
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portNVIC_SHPR3_REG |= portNVIC_PENDSV_PRI;
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portNVIC_SHPR3_REG |= 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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vPortSetupTimerInterrupt();
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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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/* Not implemented in ports where there is nothing to return to.
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* Artificially force an assert. */
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configASSERT( uxCriticalNesting == 1000UL );
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}
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/*-----------------------------------------------------------*/
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void vPortYield( void )
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{
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/* Set a PendSV to request a context switch. */
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portNVIC_INT_CTRL_REG = portNVIC_PENDSVSET;
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/* Barriers are normally not required but do ensure the code is completely
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* within the specified behaviour for the architecture. */
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__DSB();
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__ISB();
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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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__DSB();
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__ISB();
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}
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/*-----------------------------------------------------------*/
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void vPortExitCritical( void )
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{
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configASSERT( uxCriticalNesting );
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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 xPortSysTickHandler( void )
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{
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uint32_t ulPreviousMask;
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ulPreviousMask = portSET_INTERRUPT_MASK_FROM_ISR();
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{
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/* Increment the RTOS tick. */
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if( xTaskIncrementTick() != pdFALSE )
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{
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/* Pend a context switch. */
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portNVIC_INT_CTRL_REG = portNVIC_PENDSVSET;
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}
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}
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portCLEAR_INTERRUPT_MASK_FROM_ISR( ulPreviousMask );
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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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__weak void vPortSetupTimerInterrupt( void )
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{
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/* Calculate the constants required to configure the tick interrupt. */
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#if ( configUSE_TICKLESS_IDLE == 1 )
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{
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ulTimerCountsForOneTick = ( configSYSTICK_CLOCK_HZ / configTICK_RATE_HZ );
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xMaximumPossibleSuppressedTicks = portMAX_24_BIT_NUMBER / ulTimerCountsForOneTick;
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ulStoppedTimerCompensation = portMISSED_COUNTS_FACTOR / ( configCPU_CLOCK_HZ / configSYSTICK_CLOCK_HZ );
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}
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#endif /* configUSE_TICKLESS_IDLE */
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/* Stop and reset the SysTick. */
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portNVIC_SYSTICK_CTRL_REG = 0UL;
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portNVIC_SYSTICK_CURRENT_VALUE_REG = 0UL;
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/* Configure SysTick to interrupt at the requested rate. */
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portNVIC_SYSTICK_LOAD_REG = ( configSYSTICK_CLOCK_HZ / configTICK_RATE_HZ ) - 1UL;
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portNVIC_SYSTICK_CTRL_REG = portNVIC_SYSTICK_CLK_BIT | portNVIC_SYSTICK_INT_BIT | portNVIC_SYSTICK_ENABLE_BIT;
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}
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/*-----------------------------------------------------------*/
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#if ( configUSE_TICKLESS_IDLE == 1 )
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__weak void vPortSuppressTicksAndSleep( TickType_t xExpectedIdleTime )
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{
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uint32_t ulReloadValue, ulCompleteTickPeriods, ulCompletedSysTickDecrements;
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TickType_t xModifiableIdleTime;
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/* Make sure the SysTick reload value does not overflow the counter. */
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if( xExpectedIdleTime > xMaximumPossibleSuppressedTicks )
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{
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xExpectedIdleTime = xMaximumPossibleSuppressedTicks;
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}
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/* Stop the SysTick momentarily. The time the SysTick is stopped for
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* is accounted for as best it can be, but using the tickless mode will
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* inevitably result in some tiny drift of the time maintained by the
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* kernel with respect to calendar time. */
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portNVIC_SYSTICK_CTRL_REG &= ~portNVIC_SYSTICK_ENABLE_BIT;
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/* Calculate the reload value required to wait xExpectedIdleTime
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* tick periods. -1 is used because this code will execute part way
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* through one of the tick periods. */
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ulReloadValue = portNVIC_SYSTICK_CURRENT_VALUE_REG + ( ulTimerCountsForOneTick * ( xExpectedIdleTime - 1UL ) );
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if( ulReloadValue > ulStoppedTimerCompensation )
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{
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ulReloadValue -= ulStoppedTimerCompensation;
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}
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/* Enter a critical section but don't use the taskENTER_CRITICAL()
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* method as that will mask interrupts that should exit sleep mode. */
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__disable_interrupt();
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__DSB();
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__ISB();
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/* If a context switch is pending or a task is waiting for the scheduler
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* to be unsuspended then abandon the low power entry. */
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if( eTaskConfirmSleepModeStatus() == eAbortSleep )
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{
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/* Restart from whatever is left in the count register to complete
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* this tick period. */
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portNVIC_SYSTICK_LOAD_REG = portNVIC_SYSTICK_CURRENT_VALUE_REG;
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/* Restart SysTick. */
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portNVIC_SYSTICK_CTRL_REG |= portNVIC_SYSTICK_ENABLE_BIT;
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/* Reset the reload register to the value required for normal tick
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* periods. */
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portNVIC_SYSTICK_LOAD_REG = ulTimerCountsForOneTick - 1UL;
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/* Re-enable interrupts - see comments above __disable_interrupt()
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* call above. */
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__enable_interrupt();
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}
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else
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{
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/* Set the new reload value. */
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portNVIC_SYSTICK_LOAD_REG = ulReloadValue;
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/* Clear the SysTick count flag and set the count value back to
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* zero. */
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portNVIC_SYSTICK_CURRENT_VALUE_REG = 0UL;
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/* Restart SysTick. */
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portNVIC_SYSTICK_CTRL_REG |= portNVIC_SYSTICK_ENABLE_BIT;
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/* Sleep until something happens. configPRE_SLEEP_PROCESSING() can
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* set its parameter to 0 to indicate that its implementation contains
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* its own wait for interrupt or wait for event instruction, and so wfi
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* should not be executed again. However, the original expected idle
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* time variable must remain unmodified, so a copy is taken. */
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xModifiableIdleTime = xExpectedIdleTime;
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configPRE_SLEEP_PROCESSING( xModifiableIdleTime );
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if( xModifiableIdleTime > 0 )
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{
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__DSB();
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__WFI();
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__ISB();
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}
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configPOST_SLEEP_PROCESSING( xExpectedIdleTime );
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/* Re-enable interrupts to allow the interrupt that brought the MCU
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* out of sleep mode to execute immediately. see comments above
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* __disable_interrupt() call above. */
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__enable_interrupt();
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__DSB();
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__ISB();
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/* Disable interrupts again because the clock is about to be stopped
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* and interrupts that execute while the clock is stopped will increase
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* any slippage between the time maintained by the RTOS and calendar
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* time. */
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__disable_interrupt();
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__DSB();
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__ISB();
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/* Disable the SysTick clock without reading the
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* portNVIC_SYSTICK_CTRL_REG register to ensure the
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* portNVIC_SYSTICK_COUNT_FLAG_BIT is not cleared if it is set. Again,
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* the time the SysTick is stopped for is accounted for as best it can
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* be, but using the tickless mode will inevitably result in some tiny
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* drift of the time maintained by the kernel with respect to calendar
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* time*/
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portNVIC_SYSTICK_CTRL_REG = ( portNVIC_SYSTICK_CLK_BIT | portNVIC_SYSTICK_INT_BIT );
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/* Determine if the SysTick clock has already counted to zero and
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* been set back to the current reload value (the reload back being
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* correct for the entire expected idle time) or if the SysTick is yet
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* to count to zero (in which case an interrupt other than the SysTick
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* must have brought the system out of sleep mode). */
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if( ( portNVIC_SYSTICK_CTRL_REG & portNVIC_SYSTICK_COUNT_FLAG_BIT ) != 0 )
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{
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uint32_t ulCalculatedLoadValue;
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/* The tick interrupt is already pending, and the SysTick count
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* reloaded with ulReloadValue. Reset the
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* portNVIC_SYSTICK_LOAD_REG with whatever remains of this tick
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* period. */
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ulCalculatedLoadValue = ( ulTimerCountsForOneTick - 1UL ) - ( ulReloadValue - portNVIC_SYSTICK_CURRENT_VALUE_REG );
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/* Don't allow a tiny value, or values that have somehow
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* underflowed because the post sleep hook did something
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* that took too long. */
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if( ( ulCalculatedLoadValue < ulStoppedTimerCompensation ) || ( ulCalculatedLoadValue > ulTimerCountsForOneTick ) )
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{
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ulCalculatedLoadValue = ( ulTimerCountsForOneTick - 1UL );
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}
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portNVIC_SYSTICK_LOAD_REG = ulCalculatedLoadValue;
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/* As the pending tick will be processed as soon as this
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* function exits, the tick value maintained by the tick is stepped
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* forward by one less than the time spent waiting. */
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ulCompleteTickPeriods = xExpectedIdleTime - 1UL;
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}
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else
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{
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/* Something other than the tick interrupt ended the sleep.
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* Work out how long the sleep lasted rounded to complete tick
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* periods (not the ulReload value which accounted for part
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* ticks). */
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ulCompletedSysTickDecrements = ( xExpectedIdleTime * ulTimerCountsForOneTick ) - portNVIC_SYSTICK_CURRENT_VALUE_REG;
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/* How many complete tick periods passed while the processor
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* was waiting? */
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ulCompleteTickPeriods = ulCompletedSysTickDecrements / ulTimerCountsForOneTick;
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/* The reload value is set to whatever fraction of a single tick
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* period remains. */
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portNVIC_SYSTICK_LOAD_REG = ( ( ulCompleteTickPeriods + 1UL ) * ulTimerCountsForOneTick ) - ulCompletedSysTickDecrements;
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}
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/* Restart SysTick so it runs from portNVIC_SYSTICK_LOAD_REG
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* again, then set portNVIC_SYSTICK_LOAD_REG back to its standard
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* value. */
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portNVIC_SYSTICK_CURRENT_VALUE_REG = 0UL;
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portNVIC_SYSTICK_CTRL_REG |= portNVIC_SYSTICK_ENABLE_BIT;
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vTaskStepTick( ulCompleteTickPeriods );
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portNVIC_SYSTICK_LOAD_REG = ulTimerCountsForOneTick - 1UL;
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/* Exit with interrpts enabled. */
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__enable_interrupt();
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}
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}
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#endif /* configUSE_TICKLESS_IDLE */
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