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 /*-----------------------------------------------------------
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30 * Implementation of functions defined in portable.h for the ARM CM4F port.
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31 *----------------------------------------------------------*/
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33 /* Scheduler includes. */
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34 #include "FreeRTOS.h"
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37 #if( configMAX_SYSCALL_INTERRUPT_PRIORITY == 0 )
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38 #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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41 #ifndef configSYSTICK_CLOCK_HZ
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42 #define configSYSTICK_CLOCK_HZ configCPU_CLOCK_HZ
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43 /* Ensure the SysTick is clocked at the same frequency as the core. */
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44 #define portNVIC_SYSTICK_CLK_BIT ( 1UL << 2UL )
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46 /* The way the SysTick is clocked is not modified in case it is not the same
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48 #define portNVIC_SYSTICK_CLK_BIT ( 0 )
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51 /* Constants required to manipulate the core. Registers first... */
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52 #define portNVIC_SYSTICK_CTRL_REG ( * ( ( volatile uint32_t * ) 0xe000e010 ) )
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53 #define portNVIC_SYSTICK_LOAD_REG ( * ( ( volatile uint32_t * ) 0xe000e014 ) )
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54 #define portNVIC_SYSTICK_CURRENT_VALUE_REG ( * ( ( volatile uint32_t * ) 0xe000e018 ) )
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55 #define portNVIC_SYSPRI2_REG ( * ( ( volatile uint32_t * ) 0xe000ed20 ) )
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56 /* ...then bits in the registers. */
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57 #define portNVIC_SYSTICK_INT_BIT ( 1UL << 1UL )
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58 #define portNVIC_SYSTICK_ENABLE_BIT ( 1UL << 0UL )
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59 #define portNVIC_SYSTICK_COUNT_FLAG_BIT ( 1UL << 16UL )
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60 #define portNVIC_PENDSVCLEAR_BIT ( 1UL << 27UL )
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61 #define portNVIC_PEND_SYSTICK_CLEAR_BIT ( 1UL << 25UL )
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63 #define portNVIC_PENDSV_PRI ( ( ( uint32_t ) configKERNEL_INTERRUPT_PRIORITY ) << 16UL )
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64 #define portNVIC_SYSTICK_PRI ( ( ( uint32_t ) configKERNEL_INTERRUPT_PRIORITY ) << 24UL )
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66 /* Constants required to check the validity of an interrupt priority. */
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67 #define portFIRST_USER_INTERRUPT_NUMBER ( 16 )
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68 #define portNVIC_IP_REGISTERS_OFFSET_16 ( 0xE000E3F0 )
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69 #define portAIRCR_REG ( * ( ( volatile uint32_t * ) 0xE000ED0C ) )
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70 #define portMAX_8_BIT_VALUE ( ( uint8_t ) 0xff )
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71 #define portTOP_BIT_OF_BYTE ( ( uint8_t ) 0x80 )
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72 #define portMAX_PRIGROUP_BITS ( ( uint8_t ) 7 )
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73 #define portPRIORITY_GROUP_MASK ( 0x07UL << 8UL )
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74 #define portPRIGROUP_SHIFT ( 8UL )
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76 /* Masks off all bits but the VECTACTIVE bits in the ICSR register. */
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77 #define portVECTACTIVE_MASK ( 0xFFUL )
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79 /* Constants required to set up the initial stack. */
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80 #define portINITIAL_XPSR ( 0x01000000 )
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82 /* The systick is a 24-bit counter. */
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83 #define portMAX_24_BIT_NUMBER ( 0xffffffUL )
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85 /* A fiddle factor to estimate the number of SysTick counts that would have
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86 occurred while the SysTick counter is stopped during tickless idle
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88 #define portMISSED_COUNTS_FACTOR ( 45UL )
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90 /* For strict compliance with the Cortex-M spec the task start address should
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91 have bit-0 clear, as it is loaded into the PC on exit from an ISR. */
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92 #define portSTART_ADDRESS_MASK ( ( StackType_t ) 0xfffffffeUL )
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95 * Setup the timer to generate the tick interrupts. The implementation in this
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96 * file is weak to allow application writers to change the timer used to
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97 * generate the tick interrupt.
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99 void vPortSetupTimerInterrupt( void );
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102 * Exception handlers.
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104 void xPortSysTickHandler( void );
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107 * Start first task is a separate function so it can be tested in isolation.
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109 extern void vPortStartFirstTask( void );
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112 * Used to catch tasks that attempt to return from their implementing function.
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114 static void prvTaskExitError( void );
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116 /*-----------------------------------------------------------*/
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118 /* Required to allow portasm.asm access the configMAX_SYSCALL_INTERRUPT_PRIORITY
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120 const uint32_t ulMaxSyscallInterruptPriority = configMAX_SYSCALL_INTERRUPT_PRIORITY;
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122 /* Each task maintains its own interrupt status in the critical nesting
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124 static UBaseType_t uxCriticalNesting = 0xaaaaaaaa;
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127 * The number of SysTick increments that make up one tick period.
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129 #if( configUSE_TICKLESS_IDLE == 1 )
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130 static uint32_t ulTimerCountsForOneTick = 0;
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131 #endif /* configUSE_TICKLESS_IDLE */
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134 * The maximum number of tick periods that can be suppressed is limited by the
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135 * 24 bit resolution of the SysTick timer.
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137 #if( configUSE_TICKLESS_IDLE == 1 )
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138 static uint32_t xMaximumPossibleSuppressedTicks = 0;
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139 #endif /* configUSE_TICKLESS_IDLE */
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142 * Compensate for the CPU cycles that pass while the SysTick is stopped (low
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143 * power functionality only.
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145 #if( configUSE_TICKLESS_IDLE == 1 )
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146 static uint32_t ulStoppedTimerCompensation = 0;
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147 #endif /* configUSE_TICKLESS_IDLE */
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150 * Used by the portASSERT_IF_INTERRUPT_PRIORITY_INVALID() macro to ensure
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151 * FreeRTOS API functions are not called from interrupts that have been assigned
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152 * a priority above configMAX_SYSCALL_INTERRUPT_PRIORITY.
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154 #if ( configASSERT_DEFINED == 1 )
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155 static uint8_t ucMaxSysCallPriority = 0;
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156 static uint32_t ulMaxPRIGROUPValue = 0;
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157 static const volatile uint8_t * const pcInterruptPriorityRegisters = ( uint8_t * ) portNVIC_IP_REGISTERS_OFFSET_16;
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158 #endif /* configASSERT_DEFINED */
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160 /*-----------------------------------------------------------*/
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163 * See header file for description.
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165 StackType_t * pxPortInitialiseStack( StackType_t * pxTopOfStack,
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166 TaskFunction_t pxCode,
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167 void * pvParameters )
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169 /* Simulate the stack frame as it would be created by a context switch
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172 /* Offset added to account for the way the MCU uses the stack on entry/exit
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173 of interrupts, and to ensure alignment. */
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176 *pxTopOfStack = portINITIAL_XPSR; /* xPSR */
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178 *pxTopOfStack = ( ( StackType_t ) pxCode ) & portSTART_ADDRESS_MASK; /* PC */
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180 *pxTopOfStack = ( StackType_t ) prvTaskExitError; /* LR */
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182 /* Save code space by skipping register initialisation. */
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183 pxTopOfStack -= 5; /* R12, R3, R2 and R1. */
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184 *pxTopOfStack = ( StackType_t ) pvParameters; /* R0 */
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186 pxTopOfStack -= 8; /* R11, R10, R9, R8, R7, R6, R5 and R4. */
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188 return pxTopOfStack;
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190 /*-----------------------------------------------------------*/
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192 static void prvTaskExitError( void )
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194 /* A function that implements a task must not exit or attempt to return to
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195 its caller as there is nothing to return to. If a task wants to exit it
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196 should instead call vTaskDelete( NULL ).
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198 Artificially force an assert() to be triggered if configASSERT() is
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199 defined, then stop here so application writers can catch the error. */
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200 configASSERT( uxCriticalNesting == ~0UL );
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201 portDISABLE_INTERRUPTS();
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204 /*-----------------------------------------------------------*/
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207 * See header file for description.
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209 BaseType_t xPortStartScheduler( void )
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211 #if( configASSERT_DEFINED == 1 )
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213 volatile uint32_t ulOriginalPriority;
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214 volatile uint8_t * const pucFirstUserPriorityRegister = ( uint8_t * ) ( portNVIC_IP_REGISTERS_OFFSET_16 + portFIRST_USER_INTERRUPT_NUMBER );
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215 volatile uint8_t ucMaxPriorityValue;
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217 /* Determine the maximum priority from which ISR safe FreeRTOS API
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218 functions can be called. ISR safe functions are those that end in
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219 "FromISR". FreeRTOS maintains separate thread and ISR API functions to
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220 ensure interrupt entry is as fast and simple as possible.
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222 Save the interrupt priority value that is about to be clobbered. */
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223 ulOriginalPriority = *pucFirstUserPriorityRegister;
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225 /* Determine the number of priority bits available. First write to all
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227 *pucFirstUserPriorityRegister = portMAX_8_BIT_VALUE;
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229 /* Read the value back to see how many bits stuck. */
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230 ucMaxPriorityValue = *pucFirstUserPriorityRegister;
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232 /* Use the same mask on the maximum system call priority. */
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233 ucMaxSysCallPriority = configMAX_SYSCALL_INTERRUPT_PRIORITY & ucMaxPriorityValue;
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235 /* Calculate the maximum acceptable priority group value for the number
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236 of bits read back. */
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237 ulMaxPRIGROUPValue = portMAX_PRIGROUP_BITS;
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238 while( ( ucMaxPriorityValue & portTOP_BIT_OF_BYTE ) == portTOP_BIT_OF_BYTE )
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240 ulMaxPRIGROUPValue--;
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241 ucMaxPriorityValue <<= ( uint8_t ) 0x01;
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244 #ifdef __NVIC_PRIO_BITS
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246 /* Check the CMSIS configuration that defines the number of
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247 priority bits matches the number of priority bits actually queried
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248 from the hardware. */
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249 configASSERT( ( portMAX_PRIGROUP_BITS - ulMaxPRIGROUPValue ) == __NVIC_PRIO_BITS );
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253 #ifdef configPRIO_BITS
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255 /* Check the FreeRTOS configuration that defines the number of
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256 priority bits matches the number of priority bits actually queried
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257 from the hardware. */
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258 configASSERT( ( portMAX_PRIGROUP_BITS - ulMaxPRIGROUPValue ) == configPRIO_BITS );
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262 /* Shift the priority group value back to its position within the AIRCR
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264 ulMaxPRIGROUPValue <<= portPRIGROUP_SHIFT;
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265 ulMaxPRIGROUPValue &= portPRIORITY_GROUP_MASK;
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267 /* Restore the clobbered interrupt priority register to its original
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269 *pucFirstUserPriorityRegister = ulOriginalPriority;
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271 #endif /* conifgASSERT_DEFINED */
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273 /* Make PendSV and SysTick the lowest priority interrupts. */
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274 portNVIC_SYSPRI2_REG |= portNVIC_PENDSV_PRI;
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275 portNVIC_SYSPRI2_REG |= portNVIC_SYSTICK_PRI;
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277 /* Start the timer that generates the tick ISR. Interrupts are disabled
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279 vPortSetupTimerInterrupt();
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281 /* Initialise the critical nesting count ready for the first task. */
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282 uxCriticalNesting = 0;
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284 /* Start the first task. */
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285 vPortStartFirstTask();
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287 /* Should not get here! */
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290 /*-----------------------------------------------------------*/
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292 void vPortEndScheduler( void )
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294 /* Not implemented in ports where there is nothing to return to.
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295 Artificially force an assert. */
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296 configASSERT( uxCriticalNesting == 1000UL );
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298 /*-----------------------------------------------------------*/
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300 void vPortEnterCritical( void )
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302 portDISABLE_INTERRUPTS();
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303 uxCriticalNesting++;
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305 /* This is not the interrupt safe version of the enter critical function so
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306 assert() if it is being called from an interrupt context. Only API
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307 functions that end in "FromISR" can be used in an interrupt. Only assert if
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308 the critical nesting count is 1 to protect against recursive calls if the
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309 assert function also uses a critical section. */
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310 if( uxCriticalNesting == 1 )
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312 configASSERT( ( portNVIC_INT_CTRL_REG & portVECTACTIVE_MASK ) == 0 );
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315 /*-----------------------------------------------------------*/
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317 void vPortExitCritical( void )
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319 configASSERT( uxCriticalNesting );
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320 uxCriticalNesting--;
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321 if( uxCriticalNesting == 0 )
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323 portENABLE_INTERRUPTS();
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326 /*-----------------------------------------------------------*/
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328 void xPortSysTickHandler( void )
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330 /* The SysTick runs at the lowest interrupt priority, so when this interrupt
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331 executes all interrupts must be unmasked. There is therefore no need to
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332 save and then restore the interrupt mask value as its value is already
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334 ( void ) portSET_INTERRUPT_MASK_FROM_ISR();
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336 /* Increment the RTOS tick. */
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337 if( xTaskIncrementTick() != pdFALSE )
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339 /* A context switch is required. Context switching is performed in
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340 the PendSV interrupt. Pend the PendSV interrupt. */
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341 portNVIC_INT_CTRL_REG = portNVIC_PENDSVSET_BIT;
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344 portCLEAR_INTERRUPT_MASK_FROM_ISR( 0 );
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346 /*-----------------------------------------------------------*/
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348 #if( configUSE_TICKLESS_IDLE == 1 )
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350 #pragma WEAK( vPortSuppressTicksAndSleep )
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351 void vPortSuppressTicksAndSleep( TickType_t xExpectedIdleTime )
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353 uint32_t ulReloadValue, ulCompleteTickPeriods, ulCompletedSysTickDecrements;
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354 TickType_t xModifiableIdleTime;
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356 /* Make sure the SysTick reload value does not overflow the counter. */
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357 if( xExpectedIdleTime > xMaximumPossibleSuppressedTicks )
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359 xExpectedIdleTime = xMaximumPossibleSuppressedTicks;
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362 /* Stop the SysTick momentarily. The time the SysTick is stopped for
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363 is accounted for as best it can be, but using the tickless mode will
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364 inevitably result in some tiny drift of the time maintained by the
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365 kernel with respect to calendar time. */
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366 portNVIC_SYSTICK_CTRL_REG &= ~portNVIC_SYSTICK_ENABLE_BIT;
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368 /* Calculate the reload value required to wait xExpectedIdleTime
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369 tick periods. -1 is used because this code will execute part way
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370 through one of the tick periods. */
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371 ulReloadValue = portNVIC_SYSTICK_CURRENT_VALUE_REG + ( ulTimerCountsForOneTick * ( xExpectedIdleTime - 1UL ) );
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372 if( ulReloadValue > ulStoppedTimerCompensation )
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374 ulReloadValue -= ulStoppedTimerCompensation;
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377 /* Enter a critical section but don't use the taskENTER_CRITICAL()
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378 method as that will mask interrupts that should exit sleep mode. */
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379 __asm( " cpsid i" );
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384 /* If a context switch is pending or a task is waiting for the scheduler
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385 to be unsuspended then abandon the low power entry. */
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386 if( eTaskConfirmSleepModeStatus() == eAbortSleep )
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388 /* Restart from whatever is left in the count register to complete
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389 this tick period. */
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390 portNVIC_SYSTICK_LOAD_REG = portNVIC_SYSTICK_CURRENT_VALUE_REG;
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392 /* Restart SysTick. */
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393 portNVIC_SYSTICK_CTRL_REG |= portNVIC_SYSTICK_ENABLE_BIT;
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395 /* Reset the reload register to the value required for normal tick
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397 portNVIC_SYSTICK_LOAD_REG = ulTimerCountsForOneTick - 1UL;
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399 /* Re-enable interrupts - see comments above __disable_interrupt()
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401 __asm( " cpsie i" );
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405 /* Set the new reload value. */
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406 portNVIC_SYSTICK_LOAD_REG = ulReloadValue;
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408 /* Clear the SysTick count flag and set the count value back to
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410 portNVIC_SYSTICK_CURRENT_VALUE_REG = 0UL;
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412 /* Restart SysTick. */
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413 portNVIC_SYSTICK_CTRL_REG |= portNVIC_SYSTICK_ENABLE_BIT;
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415 /* Sleep until something happens. configPRE_SLEEP_PROCESSING() can
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416 set its parameter to 0 to indicate that its implementation contains
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417 its own wait for interrupt or wait for event instruction, and so wfi
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418 should not be executed again. However, the original expected idle
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419 time variable must remain unmodified, so a copy is taken. */
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420 xModifiableIdleTime = xExpectedIdleTime;
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421 configPRE_SLEEP_PROCESSING( xModifiableIdleTime );
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422 if( xModifiableIdleTime > 0 )
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428 configPOST_SLEEP_PROCESSING( xExpectedIdleTime );
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430 /* Re-enable interrupts to allow the interrupt that brought the MCU
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431 out of sleep mode to execute immediately. see comments above
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432 __disable_interrupt() call above. */
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433 __asm( " cpsie i" );
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437 /* Disable interrupts again because the clock is about to be stopped
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438 and interrupts that execute while the clock is stopped will increase
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439 any slippage between the time maintained by the RTOS and calendar
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441 __asm( " cpsid i" );
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445 /* Disable the SysTick clock without reading the
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446 portNVIC_SYSTICK_CTRL_REG register to ensure the
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447 portNVIC_SYSTICK_COUNT_FLAG_BIT is not cleared if it is set. Again,
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448 the time the SysTick is stopped for is accounted for as best it can
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449 be, but using the tickless mode will inevitably result in some tiny
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450 drift of the time maintained by the kernel with respect to calendar
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452 portNVIC_SYSTICK_CTRL_REG = ( portNVIC_SYSTICK_CLK_BIT | portNVIC_SYSTICK_INT_BIT );
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454 /* Determine if the SysTick clock has already counted to zero and
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455 been set back to the current reload value (the reload back being
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456 correct for the entire expected idle time) or if the SysTick is yet
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457 to count to zero (in which case an interrupt other than the SysTick
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458 must have brought the system out of sleep mode). */
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459 if( ( portNVIC_SYSTICK_CTRL_REG & portNVIC_SYSTICK_COUNT_FLAG_BIT ) != 0 )
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461 uint32_t ulCalculatedLoadValue;
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463 /* The tick interrupt is already pending, and the SysTick count
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464 reloaded with ulReloadValue. Reset the
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465 portNVIC_SYSTICK_LOAD_REG with whatever remains of this tick
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467 ulCalculatedLoadValue = ( ulTimerCountsForOneTick - 1UL ) - ( ulReloadValue - portNVIC_SYSTICK_CURRENT_VALUE_REG );
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469 /* Don't allow a tiny value, or values that have somehow
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470 underflowed because the post sleep hook did something
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471 that took too long. */
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472 if( ( ulCalculatedLoadValue < ulStoppedTimerCompensation ) || ( ulCalculatedLoadValue > ulTimerCountsForOneTick ) )
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474 ulCalculatedLoadValue = ( ulTimerCountsForOneTick - 1UL );
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477 portNVIC_SYSTICK_LOAD_REG = ulCalculatedLoadValue;
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479 /* As the pending tick will be processed as soon as this
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480 function exits, the tick value maintained by the tick is stepped
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481 forward by one less than the time spent waiting. */
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482 ulCompleteTickPeriods = xExpectedIdleTime - 1UL;
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486 /* Something other than the tick interrupt ended the sleep.
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487 Work out how long the sleep lasted rounded to complete tick
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488 periods (not the ulReload value which accounted for part
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490 ulCompletedSysTickDecrements = ( xExpectedIdleTime * ulTimerCountsForOneTick ) - portNVIC_SYSTICK_CURRENT_VALUE_REG;
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492 /* How many complete tick periods passed while the processor
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494 ulCompleteTickPeriods = ulCompletedSysTickDecrements / ulTimerCountsForOneTick;
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496 /* The reload value is set to whatever fraction of a single tick
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498 portNVIC_SYSTICK_LOAD_REG = ( ( ulCompleteTickPeriods + 1UL ) * ulTimerCountsForOneTick ) - ulCompletedSysTickDecrements;
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501 /* Restart SysTick so it runs from portNVIC_SYSTICK_LOAD_REG
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502 again, then set portNVIC_SYSTICK_LOAD_REG back to its standard
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504 portNVIC_SYSTICK_CURRENT_VALUE_REG = 0UL;
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505 portNVIC_SYSTICK_CTRL_REG |= portNVIC_SYSTICK_ENABLE_BIT;
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506 vTaskStepTick( ulCompleteTickPeriods );
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507 portNVIC_SYSTICK_LOAD_REG = ulTimerCountsForOneTick - 1UL;
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509 /* Exit with interrpts enabled. */
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510 __asm( " cpsie i" );
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514 #endif /* configUSE_TICKLESS_IDLE */
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515 /*-----------------------------------------------------------*/
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518 * Setup the systick timer to generate the tick interrupts at the required
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521 #pragma WEAK( vPortSetupTimerInterrupt )
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522 void vPortSetupTimerInterrupt( void )
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524 /* Calculate the constants required to configure the tick interrupt. */
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525 #if( configUSE_TICKLESS_IDLE == 1 )
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527 ulTimerCountsForOneTick = ( configSYSTICK_CLOCK_HZ / configTICK_RATE_HZ );
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528 xMaximumPossibleSuppressedTicks = portMAX_24_BIT_NUMBER / ulTimerCountsForOneTick;
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529 ulStoppedTimerCompensation = portMISSED_COUNTS_FACTOR / ( configCPU_CLOCK_HZ / configSYSTICK_CLOCK_HZ );
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531 #endif /* configUSE_TICKLESS_IDLE */
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533 /* Stop and clear the SysTick. */
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534 portNVIC_SYSTICK_CTRL_REG = 0UL;
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535 portNVIC_SYSTICK_CURRENT_VALUE_REG = 0UL;
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537 /* Configure SysTick to interrupt at the requested rate. */
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538 portNVIC_SYSTICK_LOAD_REG = ( configSYSTICK_CLOCK_HZ / configTICK_RATE_HZ ) - 1UL;
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539 portNVIC_SYSTICK_CTRL_REG = ( portNVIC_SYSTICK_CLK_BIT | portNVIC_SYSTICK_INT_BIT | portNVIC_SYSTICK_ENABLE_BIT );
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541 /*-----------------------------------------------------------*/
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543 #if( configASSERT_DEFINED == 1 )
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545 void vPortValidateInterruptPriority( void )
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547 extern uint32_t ulPortGetIPSR( void );
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548 uint32_t ulCurrentInterrupt;
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549 uint8_t ucCurrentPriority;
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551 ulCurrentInterrupt = ulPortGetIPSR();
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553 /* Is the interrupt number a user defined interrupt? */
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554 if( ulCurrentInterrupt >= portFIRST_USER_INTERRUPT_NUMBER )
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556 /* Look up the interrupt's priority. */
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557 ucCurrentPriority = pcInterruptPriorityRegisters[ ulCurrentInterrupt ];
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559 /* The following assertion will fail if a service routine (ISR) for
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560 an interrupt that has been assigned a priority above
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561 configMAX_SYSCALL_INTERRUPT_PRIORITY calls an ISR safe FreeRTOS API
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562 function. ISR safe FreeRTOS API functions must *only* be called
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563 from interrupts that have been assigned a priority at or below
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564 configMAX_SYSCALL_INTERRUPT_PRIORITY.
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566 Numerically low interrupt priority numbers represent logically high
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567 interrupt priorities, therefore the priority of the interrupt must
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568 be set to a value equal to or numerically *higher* than
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569 configMAX_SYSCALL_INTERRUPT_PRIORITY.
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571 Interrupts that use the FreeRTOS API must not be left at their
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572 default priority of zero as that is the highest possible priority,
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573 which is guaranteed to be above configMAX_SYSCALL_INTERRUPT_PRIORITY,
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574 and therefore also guaranteed to be invalid.
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576 FreeRTOS maintains separate thread and ISR API functions to ensure
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577 interrupt entry is as fast and simple as possible.
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579 The following links provide detailed information:
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580 http://www.freertos.org/RTOS-Cortex-M3-M4.html
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581 http://www.freertos.org/FAQHelp.html */
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582 configASSERT( ucCurrentPriority >= ucMaxSysCallPriority );
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585 /* Priority grouping: The interrupt controller (NVIC) allows the bits
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586 that define each interrupt's priority to be split between bits that
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587 define the interrupt's pre-emption priority bits and bits that define
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588 the interrupt's sub-priority. For simplicity all bits must be defined
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589 to be pre-emption priority bits. The following assertion will fail if
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590 this is not the case (if some bits represent a sub-priority).
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592 If the application only uses CMSIS libraries for interrupt
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593 configuration then the correct setting can be achieved on all Cortex-M
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594 devices by calling NVIC_SetPriorityGrouping( 0 ); before starting the
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595 scheduler. Note however that some vendor specific peripheral libraries
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596 assume a non-zero priority group setting, in which cases using a value
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597 of zero will result in unpredictable behaviour. */
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598 configASSERT( ( portAIRCR_REG & portPRIORITY_GROUP_MASK ) <= ulMaxPRIGROUPValue );
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601 #endif /* configASSERT_DEFINED */
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