2 * FreeRTOS Kernel V10.0.0
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3 * Copyright (C) 2017 Amazon.com, Inc. or its affiliates. All Rights Reserved.
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5 * Permission is hereby granted, free of charge, to any person obtaining a copy of
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6 * this software and associated documentation files (the "Software"), to deal in
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7 * the Software without restriction, including without limitation the rights to
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8 * use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of
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9 * the Software, and to permit persons to whom the Software is furnished to do so,
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10 * subject to the following conditions:
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12 * The above copyright notice and this permission notice shall be included in all
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13 * copies or substantial portions of the Software. If you wish to use our Amazon
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14 * FreeRTOS name, please do so in a fair use way that does not cause confusion.
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16 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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17 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS
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18 * FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR
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19 * COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER
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20 * IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
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21 * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
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23 * http://www.FreeRTOS.org
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24 * http://aws.amazon.com/freertos
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26 * 1 tab == 4 spaces!
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29 /* Standard includes. */
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32 /* FreeRTOS includes. */
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33 #include "FreeRTOS.h"
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36 /* Library includes. */
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39 /* This file contains functions that will override the default implementations
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40 in the RTOS port layer. Therefore only build this file if the low power demo
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42 #if( configCREATE_LOW_POWER_DEMO == 1 )
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44 /* ID of the hibernation timer used to generate the tick. */
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45 #define mainTICK_HTIMER_ID 0
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47 /* Written to the hibernation timer control register to configure the timer for
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48 its higher resolution. */
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49 #define mainHTIMER_HIGH_RESOLUTION 0
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51 /* The frequency of the hibernation timer when it is running at its higher
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52 resolution and low resolution respectively. */
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53 #define mainHIGHER_RESOLUTION_TIMER_HZ ( 32787 ) /* (1000000us / 30.5us) as each LSB is 30.5us. */
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54 #define mainLOW_RESOLUTION_TIMER_HZ ( 8UL ) /* ( 1000ms / 125ms ) as each LSB is 0.125s. */
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56 /* Some registers are accessed directly as the library is not compatible with
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57 all the compilers used. */
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58 #define lpHTIMER_PRELOAD_REGISTER ( * ( volatile uint16_t * ) 0x40009800 )
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59 #define lpHTIMER_COUNT_REGISTER ( * ( volatile uint16_t * ) 0x40009808 )
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60 #define lpEC_GIRQ17_ENABLE_SET ( * ( volatile uint32_t * ) 0x4000C0B8 )
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61 #define lpHTIMER_INTERRUPT_CONTROL_BIT ( 1UL << 20UL )
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64 * The low power demo does not use the SysTick, so override the
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65 * vPortSetupTickInterrupt() function with an implementation that configures
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66 * the low power clock. NOTE: This function name must not be changed as it
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67 * is called from the RTOS portable layer.
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69 void vPortSetupTimerInterrupt( void );
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71 /*-----------------------------------------------------------*/
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73 /* The reload value to use in the timer to generate the tick interrupt -
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74 assumes the timer is running at its higher resolution. */
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75 static const uint16_t usHighResolutionReloadValue = ( mainHIGHER_RESOLUTION_TIMER_HZ / ( uint16_t ) configTICK_RATE_HZ );
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77 /* Calculate how many clock increments make up a single tick period. */
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78 static const uint32_t ulReloadValueForOneHighResolutionTick = ( mainHIGHER_RESOLUTION_TIMER_HZ / configTICK_RATE_HZ );
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80 /* Calculate the maximum number of ticks that can be suppressed when using the
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81 high resolution clock and low resolution clock respectively. */
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82 static uint32_t ulMaximumPossibleSuppressedHighResolutionTicks = 0;
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84 /* As the clock is only 2KHz, it is likely a value of 1 will be too much, so
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85 use zero - but leave the value here to assist porting to different clock
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87 static const uint32_t ulStoppedTimerCompensation = 0UL;
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89 /* Flag set from the tick interrupt to allow the sleep processing to know if
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90 sleep mode was exited because of an timer interrupt or a different interrupt. */
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91 static volatile uint32_t ulTickFlag = pdFALSE;
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93 /*-----------------------------------------------------------*/
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95 void NVIC_Handler_HIB_TMR( void ) iv IVT_INT_HTIMER ics ICS_AUTO
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97 lpHTIMER_PRELOAD_REGISTER = usHighResolutionReloadValue;
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99 /* Increment the RTOS tick. */
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100 if( xTaskIncrementTick() != pdFALSE )
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102 /* A context switch is required. Context switching is performed in
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103 the PendSV interrupt. Pend the PendSV interrupt. */
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104 portNVIC_INT_CTRL_REG = portNVIC_PENDSVSET_BIT;
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107 /* The CPU woke because of a tick. */
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108 ulTickFlag = pdTRUE;
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110 /*-----------------------------------------------------------*/
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112 void vPortSetupTimerInterrupt( void )
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114 /* Cannot be a const when using the MikroC compiler. */
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115 ulMaximumPossibleSuppressedHighResolutionTicks = ( ( uint32_t ) USHRT_MAX ) / ulReloadValueForOneHighResolutionTick;
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117 /* Set up the hibernation timer to start at the value required by the
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119 htimer_enable( mainTICK_HTIMER_ID, usHighResolutionReloadValue, mainHTIMER_HIGH_RESOLUTION );
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121 /* Enable the HTIMER interrupt. Equivalent to enable_htimer0_irq(); */
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122 lpEC_GIRQ17_ENABLE_SET |= lpHTIMER_INTERRUPT_CONTROL_BIT;
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124 /* The hibernation timer is not an auto-reload timer, so gets reset
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125 from within the ISR itself. For that reason it's interrupt is set
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126 to the highest possible priority to ensure clock slippage is minimised. */
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127 NVIC_SetIntPriority( IVT_INT_HTIMER, configLIBRARY_MAX_SYSCALL_INTERRUPT_PRIORITY );
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128 NVIC_IntEnable( IVT_INT_HTIMER );
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130 /*-----------------------------------------------------------*/
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132 /* Override the default definition of vPortSuppressTicksAndSleep() that is
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133 weakly defined in the FreeRTOS Cortex-M port layer with a version that manages
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134 the hibernation timer, as the tick is generated from the low power hibernation
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135 timer and not the SysTick as would normally be the case on a Cortex-M. */
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136 void vPortSuppressTicksAndSleep( TickType_t xExpectedIdleTime )
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138 uint32_t ulCompleteTickPeriods, ulReloadValue, ulCompletedTimerDecrements, ulCountAfterSleep, ulCountBeforeSleep;
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139 eSleepModeStatus eSleepAction;
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140 TickType_t xModifiableIdleTime;
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142 /* THIS FUNCTION IS CALLED WITH THE SCHEDULER SUSPENDED. */
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144 /* Make sure the hibernation timer reload value does not overflow the
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146 if( xExpectedIdleTime > ( TickType_t ) ulMaximumPossibleSuppressedHighResolutionTicks )
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148 xExpectedIdleTime = ( TickType_t ) ulMaximumPossibleSuppressedHighResolutionTicks;
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151 /* Stop the timer momentarily. The time the timer is stopped for is
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152 accounted for as best it can be, but using the tickless mode will
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153 inevitably result in some tiny drift of the time maintained by the kernel
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154 with respect to calendar time. Take the count value first as clearing
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155 the preload value also seems to clear the count. */
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156 ulCountBeforeSleep = ( uint32_t ) lpHTIMER_COUNT_REGISTER;
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157 lpHTIMER_PRELOAD_REGISTER = 0;
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159 /* Calculate the reload value required to wait xExpectedIdleTime tick
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160 periods. -1 is used as the current time slice will already be part way
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161 through, the part value coming from the current timer count value. */
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162 ulReloadValue = ulCountBeforeSleep + ( ulReloadValueForOneHighResolutionTick * ( xExpectedIdleTime - 1UL ) );
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164 if( ulReloadValue > ulStoppedTimerCompensation )
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166 /* Compensate for the fact that the timer is going to be stopped
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168 ulReloadValue -= ulStoppedTimerCompensation;
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171 /* Enter a critical section but don't use the taskENTER_CRITICAL() method as
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172 that will mask interrupts that should exit sleep mode. */
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177 /* The tick flag is set to false before sleeping. If it is true when sleep
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178 mode is exited then sleep mode was probably exited because the tick was
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179 suppressed for the entire xExpectedIdleTime period. */
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180 ulTickFlag = pdFALSE;
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182 /* If a context switch is pending then abandon the low power entry as
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183 the context switch might have been pended by an external interrupt that
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184 requires processing. */
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185 eSleepAction = eTaskConfirmSleepModeStatus();
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186 if( eSleepAction == eAbortSleep )
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188 /* Resetart the timer from whatever remains in the counter register,
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189 but 0 is not a valid value. */
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190 ulReloadValue = ulCountBeforeSleep - ulStoppedTimerCompensation;
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192 if( ulReloadValue == 0 )
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194 ulReloadValue = ulReloadValueForOneHighResolutionTick;
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195 ulCompleteTickPeriods = 1UL;
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199 ulCompleteTickPeriods = 0UL;
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202 lpHTIMER_PRELOAD_REGISTER = ( uint16_t ) ulReloadValue;
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204 /* Re-enable interrupts - see comments above the cpsid instruction()
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213 /* Write the calculated reload value, which will also start the
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215 lpHTIMER_PRELOAD_REGISTER = ( uint16_t ) ulReloadValue;
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217 /* Allow the application to define some pre-sleep processing. */
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218 xModifiableIdleTime = xExpectedIdleTime;
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219 configPRE_SLEEP_PROCESSING( xModifiableIdleTime );
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221 /* xExpectedIdleTime being set to 0 by configPRE_SLEEP_PROCESSING()
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222 means the application defined code has already executed the sleep
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224 if( xModifiableIdleTime > 0 )
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231 /* Allow the application to define some post sleep processing. */
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232 configPOST_SLEEP_PROCESSING( xModifiableIdleTime );
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234 /* Stop the hibernation timer. Again, the time the tiemr is stopped
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235 for is accounted for as best it can be, but using the tickless mode
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236 will inevitably result in some tiny drift of the time maintained by the
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237 kernel with respect to calendar time. Take the count value first as
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238 setting the preload to zero also seems to clear the count. */
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239 ulCountAfterSleep = ( uint32_t ) lpHTIMER_COUNT_REGISTER;
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240 lpHTIMER_PRELOAD_REGISTER = 0;
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242 /* Re-enable interrupts - see comments above the cpsid instruction()
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249 if( ulTickFlag != pdFALSE )
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251 /* The tick interrupt has already executed, although because this
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252 function is called with the scheduler suspended the actual tick
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253 processing will not occur until after this function has exited.
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254 The timer has already been reloaded to count in ticks, and can just
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255 continue counting down from its current value. */
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256 ulReloadValue = ulCountAfterSleep;
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258 /* Sanity check that the timer's reload value has indeed been
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260 configASSERT( ( uint32_t ) lpHTIMER_PRELOAD_REGISTER == ulReloadValueForOneHighResolutionTick );
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262 /* The tick interrupt handler will already have pended the tick
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263 processing in the kernel. As the pending tick will be processed as
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264 soon as this function exits, the tick value maintained by the tick
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265 is stepped forward by one less than the time spent sleeping. The
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266 actual stepping of the tick appears later in this function. */
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267 ulCompleteTickPeriods = xExpectedIdleTime - 1UL;
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271 /* Something other than the tick interrupt ended the sleep. How
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272 many complete tick periods passed while the processor was
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274 ulCompletedTimerDecrements = ulReloadValue - ulCountAfterSleep;
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276 /* Undo the adjustment that was made to the reload value to account
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277 for the fact that a time slice was part way through when this
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278 function was called before working out how many complete tick
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279 periods this represents. (could have used [ulExpectedIdleTime *
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280 ulReloadValueForOneHighResolutionTick] instead of ulReloadValue on
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281 the previous line, but this way avoids the multiplication). */
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282 ulCompletedTimerDecrements += ( ulReloadValueForOneHighResolutionTick - ulCountBeforeSleep );
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283 ulCompleteTickPeriods = ulCompletedTimerDecrements / ulReloadValueForOneHighResolutionTick;
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285 /* The reload value is set to whatever fraction of a single tick
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287 ulReloadValue = ( ( ulCompleteTickPeriods + 1UL ) * ulReloadValueForOneHighResolutionTick ) - ulCompletedTimerDecrements;
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290 /* Cannot use a reload value of 0 - it will not start the timer. */
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291 if( ulReloadValue == 0 )
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293 /* There is no fraction remaining. */
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294 ulReloadValue = ulReloadValueForOneHighResolutionTick;
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295 ulCompleteTickPeriods++;
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298 /* Restart the timer so it runs down from the reload value. The reload
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299 value will get set to the value required to generate exactly one tick
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300 period the next time the tick interrupt executes. */
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301 lpHTIMER_PRELOAD_REGISTER = ( uint16_t ) ulReloadValue;
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304 /* Wind the tick forward by the number of tick periods that the CPU
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305 remained in a low power state. */
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306 vTaskStepTick( ulCompleteTickPeriods );
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308 /*-----------------------------------------------------------*/
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311 #endif /* configCREATE_LOW_POWER_DEMO */
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