2 FreeRTOS V7.2.0 - Copyright (C) 2012 Real Time Engineers Ltd.
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5 ***************************************************************************
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7 * FreeRTOS tutorial books are available in pdf and paperback. *
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8 * Complete, revised, and edited pdf reference manuals are also *
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11 * Purchasing FreeRTOS documentation will not only help you, by *
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12 * ensuring you get running as quickly as possible and with an *
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13 * in-depth knowledge of how to use FreeRTOS, it will also help *
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14 * the FreeRTOS project to continue with its mission of providing *
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15 * professional grade, cross platform, de facto standard solutions *
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16 * for microcontrollers - completely free of charge! *
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18 * >>> See http://www.FreeRTOS.org/Documentation for details. <<< *
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20 * Thank you for using FreeRTOS, and thank you for your support! *
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22 ***************************************************************************
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25 This file is part of the FreeRTOS distribution.
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27 FreeRTOS is free software; you can redistribute it and/or modify it under
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28 the terms of the GNU General Public License (version 2) as published by the
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29 Free Software Foundation AND MODIFIED BY the FreeRTOS exception.
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30 >>>NOTE<<< The modification to the GPL is included to allow you to
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31 distribute a combined work that includes FreeRTOS without being obliged to
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32 provide the source code for proprietary components outside of the FreeRTOS
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33 kernel. FreeRTOS is distributed in the hope that it will be useful, but
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34 WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
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35 or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
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36 more details. You should have received a copy of the GNU General Public
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37 License and the FreeRTOS license exception along with FreeRTOS; if not it
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38 can be viewed here: http://www.freertos.org/a00114.html and also obtained
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39 by writing to Richard Barry, contact details for whom are available on the
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44 ***************************************************************************
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46 * Having a problem? Start by reading the FAQ "My application does *
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47 * not run, what could be wrong? *
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49 * http://www.FreeRTOS.org/FAQHelp.html *
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51 ***************************************************************************
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54 http://www.FreeRTOS.org - Documentation, training, latest information,
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55 license and contact details.
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57 http://www.FreeRTOS.org/plus - A selection of FreeRTOS ecosystem products,
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58 including FreeRTOS+Trace - an indispensable productivity tool.
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60 Real Time Engineers ltd license FreeRTOS to High Integrity Systems, who sell
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61 the code with commercial support, indemnification, and middleware, under
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62 the OpenRTOS brand: http://www.OpenRTOS.com. High Integrity Systems also
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63 provide a safety engineered and independently SIL3 certified version under
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64 the SafeRTOS brand: http://www.SafeRTOS.com.
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67 /*-----------------------------------------------------------
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68 * Implementation of functions defined in portable.h for the ARM CM4F port.
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69 *----------------------------------------------------------*/
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71 /* Scheduler includes. */
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72 #include "FreeRTOS.h"
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76 #error This port can only be used when the project options are configured to enable hardware floating point support.
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79 #if configMAX_SYSCALL_INTERRUPT_PRIORITY == 0
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80 #error configMAX_SYSCALL_INTERRUPT_PRIORITY must not be set to 0. See http://www.FreeRTOS.org/RTOS-Cortex-M3-M4.html
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83 #ifndef configSYSTICK_CLOCK_HZ
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84 #define configSYSTICK_CLOCK_HZ configCPU_CLOCK_HZ
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85 #if configUSE_TICKLESS_IDLE == 1
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86 static const unsigned long ulStoppedTimerCompensation = 45UL;
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88 #else /* configSYSTICK_CLOCK_HZ */
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89 #if configUSE_TICKLESS_IDLE == 1
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90 /* Assumes the SysTick clock is slower than the CPU clock. */
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91 static const unsigned long ulStoppedTimerCompensation = 45UL / ( configCPU_CLOCK_HZ / configSYSTICK_CLOCK_HZ );
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93 #endif /* configSYSTICK_CLOCK_HZ */
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95 /* Constants required to manipulate the core. Registers first... */
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96 #define portNVIC_SYSTICK_CTRL_REG ( * ( ( volatile unsigned long * ) 0xe000e010 ) )
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97 #define portNVIC_SYSTICK_LOAD_REG ( * ( ( volatile unsigned long * ) 0xe000e014 ) )
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98 #define portNVIC_SYSTICK_CURRENT_VALUE_REG ( * ( ( volatile unsigned long * ) 0xe000e018 ) )
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99 #define portNVIC_INT_CTRL_REG ( * ( ( volatile unsigned long * ) 0xe000ed04 ) )
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100 #define portNVIC_SYSPRI2_REG ( * ( ( volatile unsigned long * ) 0xe000ed20 ) )
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101 /* ...then bits in the registers. */
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102 #define portNVIC_SYSTICK_CLK_BIT ( 1UL << 2UL )
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103 #define portNVIC_SYSTICK_INT_BIT ( 1UL << 1UL )
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104 #define portNVIC_SYSTICK_ENABLE_BIT ( 1UL << 0UL )
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105 #define portNVIC_SYSTICK_COUNT_FLAG_BIT ( 1UL << 16UL )
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106 #define portNVIC_PENDSVSET_BIT ( 1UL << 28UL )
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107 #define portNVIC_PENDSVCLEAR_BIT ( 1UL << 27UL )
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108 #define portNVIC_PEND_SYSTICK_CLEAR_BIT ( 1UL << 25UL )
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110 #define portNVIC_PENDSV_PRI ( ( ( unsigned long ) configKERNEL_INTERRUPT_PRIORITY ) << 16 )
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111 #define portNVIC_SYSTICK_PRI ( ( ( unsigned long ) configKERNEL_INTERRUPT_PRIORITY ) << 24 )
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113 /* Constants required to manipulate the VFP. */
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114 #define portFPCCR ( ( volatile unsigned long * ) 0xe000ef34 ) /* Floating point context control register. */
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115 #define portASPEN_AND_LSPEN_BITS ( 0x3UL << 30UL )
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117 /* Constants required to set up the initial stack. */
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118 #define portINITIAL_XPSR ( 0x01000000 )
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119 #define portINITIAL_EXEC_RETURN ( 0xfffffffd )
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121 /* Each task maintains its own interrupt status in the critical nesting
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123 static unsigned portBASE_TYPE uxCriticalNesting = 0xaaaaaaaa;
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126 * Setup the timer to generate the tick interrupts.
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128 static void prvSetupTimerInterrupt( void );
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131 * Exception handlers.
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133 void xPortSysTickHandler( void );
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136 * Start first task is a separate function so it can be tested in isolation.
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138 extern void vPortStartFirstTask( void );
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143 extern void vPortEnableVFP( void );
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145 /*-----------------------------------------------------------*/
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148 * The number of SysTick increments that make up one tick period.
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150 static unsigned long ulTimerReloadValueForOneTick = 0;
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153 * The maximum number of tick periods that can be suppressed is limited by the
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154 * 24 bit resolution of the SysTick timer.
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156 #if configUSE_TICKLESS_IDLE == 1
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157 static unsigned long xMaximumPossibleSuppressedTicks = 0;
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158 #endif /* configUSE_TICKLESS_IDLE */
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160 /*-----------------------------------------------------------*/
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163 * See header file for description.
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165 portSTACK_TYPE *pxPortInitialiseStack( portSTACK_TYPE *pxTopOfStack, pdTASK_CODE pxCode, void *pvParameters )
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167 /* Simulate the stack frame as it would be created by a context switch
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170 /* Offset added to account for the way the MCU uses the stack on entry/exit
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171 of interrupts, and to ensure alignment. */
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174 *pxTopOfStack = portINITIAL_XPSR; /* xPSR */
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176 *pxTopOfStack = ( portSTACK_TYPE ) pxCode; /* PC */
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178 *pxTopOfStack = 0; /* LR */
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180 /* Save code space by skipping register initialisation. */
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181 pxTopOfStack -= 5; /* R12, R3, R2 and R1. */
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182 *pxTopOfStack = ( portSTACK_TYPE ) pvParameters; /* R0 */
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184 /* A save method is being used that requires each task to maintain its
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185 own exec return value. */
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187 *pxTopOfStack = portINITIAL_EXEC_RETURN;
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189 pxTopOfStack -= 8; /* R11, R10, R9, R8, R7, R6, R5 and R4. */
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191 return pxTopOfStack;
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193 /*-----------------------------------------------------------*/
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196 * See header file for description.
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198 portBASE_TYPE xPortStartScheduler( void )
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200 /* Make PendSV and SysTick the lowest priority interrupts. */
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201 portNVIC_SYSPRI2_REG |= portNVIC_PENDSV_PRI;
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202 portNVIC_SYSPRI2_REG |= portNVIC_SYSTICK_PRI;
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204 /* Start the timer that generates the tick ISR. Interrupts are disabled
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206 prvSetupTimerInterrupt();
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208 /* Initialise the critical nesting count ready for the first task. */
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209 uxCriticalNesting = 0;
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211 /* Ensure the VFP is enabled - it should be anyway. */
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214 /* Lazy save always. */
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215 *( portFPCCR ) |= portASPEN_AND_LSPEN_BITS;
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217 /* Start the first task. */
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218 vPortStartFirstTask();
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220 /* Should not get here! */
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223 /*-----------------------------------------------------------*/
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225 void vPortEndScheduler( void )
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227 /* It is unlikely that the CM4F port will require this function as there
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228 is nothing to return to. */
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230 /*-----------------------------------------------------------*/
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232 void vPortYieldFromISR( void )
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234 /* Set a PendSV to request a context switch. */
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235 portNVIC_INT_CTRL_REG = portNVIC_PENDSVSET_BIT;
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237 /*-----------------------------------------------------------*/
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239 void vPortEnterCritical( void )
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241 portDISABLE_INTERRUPTS();
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242 uxCriticalNesting++;
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244 /*-----------------------------------------------------------*/
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246 void vPortExitCritical( void )
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248 uxCriticalNesting--;
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249 if( uxCriticalNesting == 0 )
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251 portENABLE_INTERRUPTS();
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254 /*-----------------------------------------------------------*/
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256 void xPortSysTickHandler( void )
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258 /* If using preemption, also force a context switch. */
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259 #if configUSE_PREEMPTION == 1
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260 portNVIC_INT_CTRL_REG = portNVIC_PENDSVSET_BIT;
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263 #if configUSE_TICKLESS_IDLE == 1
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264 portNVIC_SYSTICK_LOAD_REG = ulTimerReloadValueForOneTick;
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267 ( void ) portSET_INTERRUPT_MASK_FROM_ISR();
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269 vTaskIncrementTick();
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271 portCLEAR_INTERRUPT_MASK_FROM_ISR( 0 );
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273 /*-----------------------------------------------------------*/
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275 #if configUSE_TICKLESS_IDLE == 1
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277 __weak void vPortSuppressTicksAndSleep( portTickType xExpectedIdleTime )
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279 unsigned long ulReloadValue, ulCompleteTickPeriods, ulCompletedSysTickIncrements;
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281 /* Make sure the SysTick reload value does not overflow the counter. */
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282 if( xExpectedIdleTime > xMaximumPossibleSuppressedTicks )
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284 xExpectedIdleTime = xMaximumPossibleSuppressedTicks;
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287 /* Calculate the reload value required to wait xExpectedIdleTime
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288 tick periods. -1 is used because this code will execute part way
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289 through one of the tick periods, and the fraction of a tick period is
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290 accounted for later. */
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291 ulReloadValue = ( ulTimerReloadValueForOneTick * ( xExpectedIdleTime - 1UL ) );
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292 if( ulReloadValue > ulStoppedTimerCompensation )
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294 ulReloadValue -= ulStoppedTimerCompensation;
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297 /* Stop the SysTick momentarily. The time the SysTick is stopped for
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298 is accounted for as best it can be, but using the tickless mode will
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299 inevitably result in some tiny drift of the time maintained by the
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300 kernel with respect to calendar time. */
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301 portNVIC_SYSTICK_CTRL_REG = portNVIC_SYSTICK_CLK_BIT | portNVIC_SYSTICK_INT_BIT;
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303 /* If a context switch is pending then abandon the low power entry as
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304 the context switch might have been pended by an external interrupt that
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305 requires processing. */
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306 if( ( portNVIC_INT_CTRL_REG & portNVIC_PENDSVSET_BIT ) != 0 )
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308 /* Restart SysTick. */
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309 portNVIC_SYSTICK_CTRL_REG = portNVIC_SYSTICK_CLK_BIT | portNVIC_SYSTICK_INT_BIT | portNVIC_SYSTICK_ENABLE_BIT;
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313 /* Adjust the reload value to take into account that the current
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314 time slice is already partially complete. */
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315 ulReloadValue += ( portNVIC_SYSTICK_LOAD_REG - ( portNVIC_SYSTICK_LOAD_REG - portNVIC_SYSTICK_CURRENT_VALUE_REG ) );
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316 portNVIC_SYSTICK_LOAD_REG = ulReloadValue;
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318 /* Clear the SysTick count flag and set the count value back to
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320 portNVIC_SYSTICK_CURRENT_VALUE_REG = 0UL;
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322 /* Restart SysTick. */
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323 portNVIC_SYSTICK_CTRL_REG = portNVIC_SYSTICK_CLK_BIT | portNVIC_SYSTICK_INT_BIT | portNVIC_SYSTICK_ENABLE_BIT;
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325 /* Sleep until something happens. */
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326 portPRE_SLEEP_PROCESSING();
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328 portPOST_SLEEP_PROCESSING();
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330 /* Stop SysTick. Again, the time the SysTick is stopped for is
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331 accounted for as best it can be, but using the tickless mode will
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332 inevitably result in some tiny drift of the time maintained by the
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333 kernel with respect to calendar time. */
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334 portNVIC_SYSTICK_CTRL_REG = portNVIC_SYSTICK_CLK_BIT | portNVIC_SYSTICK_INT_BIT;
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336 if( ( portNVIC_SYSTICK_CTRL_REG & portNVIC_SYSTICK_COUNT_FLAG_BIT ) != 0 )
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338 /* The tick interrupt has already executed, and the SysTick
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339 count reloaded with the portNVIC_SYSTICK_LOAD_REG value.
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340 Reset the portNVIC_SYSTICK_LOAD_REG with whatever remains of
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341 this tick period. */
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342 portNVIC_SYSTICK_LOAD_REG = ulTimerReloadValueForOneTick - ( ulReloadValue - portNVIC_SYSTICK_CURRENT_VALUE_REG );
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344 /* The tick interrupt handler will already have pended the tick
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345 processing in the kernel. As the pending tick will be
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346 processed as soon as this function exits, the tick value
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347 maintained by the tick is stepped forward by one less than the
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348 time spent waiting. */
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349 ulCompleteTickPeriods = xExpectedIdleTime - 1UL;
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353 /* Something other than the tick interrupt ended the sleep.
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354 Work out how long the sleep lasted. */
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355 ulCompletedSysTickIncrements = ( xExpectedIdleTime * ulTimerReloadValueForOneTick ) - portNVIC_SYSTICK_CURRENT_VALUE_REG;
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357 /* How many complete tick periods passed while the processor
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359 ulCompleteTickPeriods = ulCompletedSysTickIncrements / ulTimerReloadValueForOneTick;
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361 /* The reload value is set to whatever fraction of a single tick
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363 portNVIC_SYSTICK_LOAD_REG = ( ( ulCompleteTickPeriods + 1 ) * ulTimerReloadValueForOneTick ) - ulCompletedSysTickIncrements;
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366 /* Restart SysTick so it runs from portNVIC_SYSTICK_LOAD_REG
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367 again, then set portNVIC_SYSTICK_LOAD_REG back to its standard
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369 portNVIC_SYSTICK_CURRENT_VALUE_REG = 0UL;
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370 portNVIC_SYSTICK_CTRL_REG = portNVIC_SYSTICK_CLK_BIT | portNVIC_SYSTICK_INT_BIT | portNVIC_SYSTICK_ENABLE_BIT;
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372 vTaskStepTick( ulCompleteTickPeriods );
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376 #endif /* #if configUSE_TICKLESS_IDLE */
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377 /*-----------------------------------------------------------*/
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380 * Setup the systick timer to generate the tick interrupts at the required
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383 void prvSetupTimerInterrupt( void )
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385 /* Configure the constants required to setup the tick interrupt. */
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386 ulTimerReloadValueForOneTick = ( configSYSTICK_CLOCK_HZ / configTICK_RATE_HZ ) - 1UL;
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387 #if configUSE_TICKLESS_IDLE == 1
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388 xMaximumPossibleSuppressedTicks = 0xffffffUL / ( ( configSYSTICK_CLOCK_HZ / configTICK_RATE_HZ ) - 1UL );
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389 #endif /* configUSE_TICKLESS_IDLE */
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391 /* Configure SysTick to interrupt at the requested rate. */
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392 portNVIC_SYSTICK_LOAD_REG = ulTimerReloadValueForOneTick;
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393 portNVIC_SYSTICK_CTRL_REG = portNVIC_SYSTICK_CLK_BIT | portNVIC_SYSTICK_INT_BIT | portNVIC_SYSTICK_ENABLE_BIT;
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395 /*-----------------------------------------------------------*/
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