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@ -34,22 +34,33 @@
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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 uint32_t * ) 0xe000e010 )
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#define portNVIC_SYSTICK_LOAD ( ( volatile uint32_t * ) 0xe000e014 )
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#define portNVIC_SYSTICK_CURRENT_VALUE ( ( volatile uint32_t * ) 0xe000e018 )
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#define portNVIC_INT_CTRL ( ( volatile uint32_t *) 0xe000ed04 )
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#define portNVIC_SYSPRI2 ( ( volatile uint32_t *) 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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#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_SYSPRI2_REG ( * ( ( volatile uint32_t * ) 0xe000ed20 ) )
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#define portNVIC_SYSTICK_CLK_BIT ( 1UL << 2UL )
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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 portNVIC_PENDSVSET_BIT ( 1UL << 28UL )
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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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/* 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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/* Constants used with memory barrier intrinsics. */
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#define portSY_FULL_READ_WRITE ( 15 )
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@ -57,6 +68,24 @@
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variable. */
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static UBaseType_t uxCriticalNesting = 0xaaaaaaaa;
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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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*/
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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.
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*/
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@ -158,8 +187,8 @@ __asm void prvPortStartFirstTask( void )
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BaseType_t xPortStartScheduler( void )
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{
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/* Make PendSV, CallSV and SysTick the same priority 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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portNVIC_SYSPRI2_REG |= portNVIC_PENDSV_PRI;
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portNVIC_SYSPRI2_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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@ -187,7 +216,7 @@ void vPortEndScheduler( void )
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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 ) = portNVIC_PENDSVSET;
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portNVIC_INT_CTRL_REG = portNVIC_PENDSVSET_BIT;
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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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@ -287,7 +316,7 @@ uint32_t ulPreviousMask;
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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) = portNVIC_PENDSVSET;
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portNVIC_INT_CTRL_REG = portNVIC_PENDSVSET_BIT;
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}
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}
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portCLEAR_INTERRUPT_MASK_FROM_ISR( ulPreviousMask );
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@ -300,13 +329,187 @@ uint32_t ulPreviousMask;
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*/
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void prvSetupTimerInterrupt( 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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ulTimerCountsForOneTick = ( configCPU_CLOCK_HZ / configTICK_RATE_HZ );
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xMaximumPossibleSuppressedTicks = portMAX_24_BIT_NUMBER / ulTimerCountsForOneTick;
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ulStoppedTimerCompensation = portMISSED_COUNTS_FACTOR;
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#endif /* configUSE_TICKLESS_IDLE */
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/* Stop and reset the SysTick. */
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*(portNVIC_SYSTICK_CTRL) = 0UL;
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*(portNVIC_SYSTICK_CURRENT_VALUE) = 0UL;
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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) = ( 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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portNVIC_SYSTICK_LOAD_REG = ( configCPU_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_irq();
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__dsb( portSY_FULL_READ_WRITE );
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__isb( portSY_FULL_READ_WRITE );
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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_irq() call
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above. */
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__enable_irq();
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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( portSY_FULL_READ_WRITE );
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__wfi();
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__isb( portSY_FULL_READ_WRITE );
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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_irq();
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__dsb( portSY_FULL_READ_WRITE );
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__isb( portSY_FULL_READ_WRITE );
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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_irq();
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__dsb( portSY_FULL_READ_WRITE );
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__isb( portSY_FULL_READ_WRITE );
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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 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
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again, then set portNVIC_SYSTICK_LOAD 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_irq();
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}
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}
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#endif /* #if configUSE_TICKLESS_IDLE */
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/*-----------------------------------------------------------*/
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Yuhui.Zheng
5 years ago