2 FreeRTOS V8.2.2 - Copyright (C) 2015 Real Time Engineers Ltd.
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5 VISIT http://www.FreeRTOS.org TO ENSURE YOU ARE USING THE LATEST VERSION.
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7 This file is part of the FreeRTOS distribution.
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9 FreeRTOS is free software; you can redistribute it and/or modify it under
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10 the terms of the GNU General Public License (version 2) as published by the
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11 Free Software Foundation >>!AND MODIFIED BY!<< the FreeRTOS exception.
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13 ***************************************************************************
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14 >>! NOTE: The modification to the GPL is included to allow you to !<<
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15 >>! distribute a combined work that includes FreeRTOS without being !<<
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16 >>! obliged to provide the source code for proprietary components !<<
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17 >>! outside of the FreeRTOS kernel. !<<
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18 ***************************************************************************
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20 FreeRTOS is distributed in the hope that it will be useful, but WITHOUT ANY
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21 WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
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22 FOR A PARTICULAR PURPOSE. Full license text is available on the following
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23 link: http://www.freertos.org/a00114.html
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25 ***************************************************************************
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27 * FreeRTOS provides completely free yet professionally developed, *
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28 * robust, strictly quality controlled, supported, and cross *
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29 * platform software that is more than just the market leader, it *
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30 * is the industry's de facto standard. *
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32 * Help yourself get started quickly while simultaneously helping *
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33 * to support the FreeRTOS project by purchasing a FreeRTOS *
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34 * tutorial book, reference manual, or both: *
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35 * http://www.FreeRTOS.org/Documentation *
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37 ***************************************************************************
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39 http://www.FreeRTOS.org/FAQHelp.html - Having a problem? Start by reading
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40 the FAQ page "My application does not run, what could be wrong?". Have you
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41 defined configASSERT()?
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43 http://www.FreeRTOS.org/support - In return for receiving this top quality
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44 embedded software for free we request you assist our global community by
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45 participating in the support forum.
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47 http://www.FreeRTOS.org/training - Investing in training allows your team to
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48 be as productive as possible as early as possible. Now you can receive
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49 FreeRTOS training directly from Richard Barry, CEO of Real Time Engineers
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50 Ltd, and the world's leading authority on the world's leading RTOS.
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52 http://www.FreeRTOS.org/plus - A selection of FreeRTOS ecosystem products,
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53 including FreeRTOS+Trace - an indispensable productivity tool, a DOS
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54 compatible FAT file system, and our tiny thread aware UDP/IP stack.
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56 http://www.FreeRTOS.org/labs - Where new FreeRTOS products go to incubate.
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57 Come and try FreeRTOS+TCP, our new open source TCP/IP stack for FreeRTOS.
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59 http://www.OpenRTOS.com - Real Time Engineers ltd. license FreeRTOS to High
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60 Integrity Systems ltd. to sell under the OpenRTOS brand. Low cost OpenRTOS
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61 licenses offer ticketed support, indemnification and commercial middleware.
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63 http://www.SafeRTOS.com - High Integrity Systems also provide a safety
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64 engineered and independently SIL3 certified version for use in safety and
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65 mission critical applications that require provable dependability.
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70 /*-----------------------------------------------------------
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71 * Implementation of functions defined in portable.h for the ARM CM0 port.
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72 *----------------------------------------------------------*/
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75 #include "intrinsics.h"
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77 /* Scheduler includes. */
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78 #include "FreeRTOS.h"
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81 /* Constants required to manipulate the NVIC. */
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82 #define portNVIC_SYSTICK_CTRL ( ( volatile uint32_t *) 0xe000e010 )
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83 #define portNVIC_SYSTICK_LOAD ( ( volatile uint32_t *) 0xe000e014 )
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84 #define portNVIC_SYSPRI2 ( ( volatile uint32_t *) 0xe000ed20 )
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85 #define portNVIC_SYSTICK_CLK 0x00000004
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86 #define portNVIC_SYSTICK_INT 0x00000002
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87 #define portNVIC_SYSTICK_ENABLE 0x00000001
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88 #define portMIN_INTERRUPT_PRIORITY ( 255UL )
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89 #define portNVIC_PENDSV_PRI ( portMIN_INTERRUPT_PRIORITY << 16UL )
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90 #define portNVIC_SYSTICK_PRI ( portMIN_INTERRUPT_PRIORITY << 24UL )
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92 /* Constants required to set up the initial stack. */
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93 #define portINITIAL_XPSR ( 0x01000000 )
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95 /* For backward compatibility, ensure configKERNEL_INTERRUPT_PRIORITY is
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96 defined. The value 255 should also ensure backward compatibility.
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97 FreeRTOS.org versions prior to V4.3.0 did not include this definition. */
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98 #ifndef configKERNEL_INTERRUPT_PRIORITY
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99 #define configKERNEL_INTERRUPT_PRIORITY 0
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102 /* Each task maintains its own interrupt status in the critical nesting
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104 static UBaseType_t uxCriticalNesting = 0xaaaaaaaa;
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107 * Setup the timer to generate the tick interrupts.
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109 static void prvSetupTimerInterrupt( void );
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112 * Exception handlers.
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114 void xPortSysTickHandler( void );
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117 * Start first task is a separate function so it can be tested in isolation.
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119 extern void vPortStartFirstTask( void );
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122 * Used to catch tasks that attempt to return from their implementing function.
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124 static void prvTaskExitError( void );
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126 /*-----------------------------------------------------------*/
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129 * See header file for description.
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131 StackType_t *pxPortInitialiseStack( StackType_t *pxTopOfStack, TaskFunction_t pxCode, void *pvParameters )
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133 /* Simulate the stack frame as it would be created by a context switch
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135 pxTopOfStack--; /* Offset added to account for the way the MCU uses the stack on entry/exit of interrupts. */
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136 *pxTopOfStack = portINITIAL_XPSR; /* xPSR */
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138 *pxTopOfStack = ( StackType_t ) pxCode; /* PC */
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140 *pxTopOfStack = ( StackType_t ) prvTaskExitError; /* LR */
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141 pxTopOfStack -= 5; /* R12, R3, R2 and R1. */
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142 *pxTopOfStack = ( StackType_t ) pvParameters; /* R0 */
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143 pxTopOfStack -= 8; /* R11..R4. */
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145 return pxTopOfStack;
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147 /*-----------------------------------------------------------*/
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149 static void prvTaskExitError( void )
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151 /* A function that implements a task must not exit or attempt to return to
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152 its caller as there is nothing to return to. If a task wants to exit it
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153 should instead call vTaskDelete( NULL ).
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155 Artificially force an assert() to be triggered if configASSERT() is
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156 defined, then stop here so application writers can catch the error. */
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157 configASSERT( uxCriticalNesting == ~0UL );
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158 portDISABLE_INTERRUPTS();
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161 /*-----------------------------------------------------------*/
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164 * See header file for description.
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166 BaseType_t xPortStartScheduler( void )
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168 /* Make PendSV and SysTick the lowest priority interrupts. */
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169 *(portNVIC_SYSPRI2) |= portNVIC_PENDSV_PRI;
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170 *(portNVIC_SYSPRI2) |= portNVIC_SYSTICK_PRI;
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172 /* Start the timer that generates the tick ISR. Interrupts are disabled
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174 prvSetupTimerInterrupt();
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176 /* Initialise the critical nesting count ready for the first task. */
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177 uxCriticalNesting = 0;
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179 /* Start the first task. */
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180 vPortStartFirstTask();
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182 /* Should not get here! */
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185 /*-----------------------------------------------------------*/
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187 void vPortEndScheduler( void )
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189 /* Not implemented in ports where there is nothing to return to.
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190 Artificially force an assert. */
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191 configASSERT( uxCriticalNesting == 1000UL );
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193 /*-----------------------------------------------------------*/
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195 void vPortYield( void )
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197 /* Set a PendSV to request a context switch. */
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198 *(portNVIC_INT_CTRL) = portNVIC_PENDSVSET;
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200 /* Barriers are normally not required but do ensure the code is completely
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201 within the specified behaviour for the architecture. */
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205 /*-----------------------------------------------------------*/
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207 void vPortEnterCritical( void )
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209 portDISABLE_INTERRUPTS();
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210 uxCriticalNesting++;
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214 /*-----------------------------------------------------------*/
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216 void vPortExitCritical( void )
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218 configASSERT( uxCriticalNesting );
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219 uxCriticalNesting--;
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220 if( uxCriticalNesting == 0 )
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222 portENABLE_INTERRUPTS();
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225 /*-----------------------------------------------------------*/
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227 void xPortSysTickHandler( void )
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229 uint32_t ulPreviousMask;
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231 ulPreviousMask = portSET_INTERRUPT_MASK_FROM_ISR();
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233 /* Increment the RTOS tick. */
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234 if( xTaskIncrementTick() != pdFALSE )
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236 /* Pend a context switch. */
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237 *(portNVIC_INT_CTRL) = portNVIC_PENDSVSET;
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240 portCLEAR_INTERRUPT_MASK_FROM_ISR( ulPreviousMask );
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242 /*-----------------------------------------------------------*/
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245 * Setup the systick timer to generate the tick interrupts at the required
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248 static void prvSetupTimerInterrupt( void )
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250 /* Configure SysTick to interrupt at the requested rate. */
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251 *(portNVIC_SYSTICK_LOAD) = ( configCPU_CLOCK_HZ / configTICK_RATE_HZ ) - 1UL;
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252 *(portNVIC_SYSTICK_CTRL) = portNVIC_SYSTICK_CLK | portNVIC_SYSTICK_INT | portNVIC_SYSTICK_ENABLE;
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254 /*-----------------------------------------------------------*/
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