2 FreeRTOS V5.4.0 - Copyright (C) 2003-2009 Richard Barry.
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4 This file is part of the FreeRTOS distribution.
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6 FreeRTOS is free software; you can redistribute it and/or modify it under
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7 the terms of the GNU General Public License (version 2) as published by the
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8 Free Software Foundation and modified by the FreeRTOS exception.
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9 **NOTE** The exception to the GPL is included to allow you to distribute a
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10 combined work that includes FreeRTOS without being obliged to provide the
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11 source code for proprietary components outside of the FreeRTOS kernel.
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12 Alternative commercial license and support terms are also available upon
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13 request. See the licensing section of http://www.FreeRTOS.org for full
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16 FreeRTOS is distributed in the hope that it will be useful, but WITHOUT
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17 ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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18 FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
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21 You should have received a copy of the GNU General Public License along
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22 with FreeRTOS; if not, write to the Free Software Foundation, Inc., 59
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23 Temple Place, Suite 330, Boston, MA 02111-1307 USA.
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26 ***************************************************************************
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28 * Looking for a quick start? Then check out the FreeRTOS eBook! *
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29 * See http://www.FreeRTOS.org/Documentation for details *
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31 ***************************************************************************
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35 Please ensure to read the configuration and relevant port sections of the
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36 online documentation.
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38 http://www.FreeRTOS.org - Documentation, latest information, license and
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41 http://www.SafeRTOS.com - A version that is certified for use in safety
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44 http://www.OpenRTOS.com - Commercial support, development, porting,
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45 licensing and training services.
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48 /*-----------------------------------------------------------
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49 * Implementation of functions defined in portable.h for the ARM CM3 port.
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50 *----------------------------------------------------------*/
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52 /* Scheduler includes. */
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53 #include "FreeRTOS.h"
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56 /* For backward compatibility, ensure configKERNEL_INTERRUPT_PRIORITY is
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57 defined. The value should also ensure backward compatibility.
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58 FreeRTOS.org versions prior to V4.4.0 did not include this definition. */
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59 #ifndef configKERNEL_INTERRUPT_PRIORITY
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60 #define configKERNEL_INTERRUPT_PRIORITY 255
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63 /* Constants required to manipulate the NVIC. */
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64 #define portNVIC_SYSTICK_CTRL ( ( volatile unsigned portLONG *) 0xe000e010 )
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65 #define portNVIC_SYSTICK_LOAD ( ( volatile unsigned portLONG *) 0xe000e014 )
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66 #define portNVIC_INT_CTRL ( ( volatile unsigned portLONG *) 0xe000ed04 )
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67 #define portNVIC_SYSPRI2 ( ( volatile unsigned portLONG *) 0xe000ed20 )
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68 #define portNVIC_SYSTICK_CLK 0x00000004
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69 #define portNVIC_SYSTICK_INT 0x00000002
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70 #define portNVIC_SYSTICK_ENABLE 0x00000001
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71 #define portNVIC_PENDSVSET 0x10000000
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72 #define portNVIC_PENDSV_PRI ( ( ( unsigned portLONG ) configKERNEL_INTERRUPT_PRIORITY ) << 16 )
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73 #define portNVIC_SYSTICK_PRI ( ( ( unsigned portLONG ) configKERNEL_INTERRUPT_PRIORITY ) << 24 )
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75 /* Constants required to set up the initial stack. */
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76 #define portINITIAL_XPSR ( 0x01000000 )
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78 /* The priority used by the kernel is assigned to a variable to make access
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79 from inline assembler easier. */
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80 const unsigned portLONG ulKernelPriority = configKERNEL_INTERRUPT_PRIORITY;
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82 /* Each task maintains its own interrupt status in the critical nesting
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84 static unsigned portBASE_TYPE uxCriticalNesting = 0xaaaaaaaa;
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87 * Setup the timer to generate the tick interrupts.
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89 static void prvSetupTimerInterrupt( void );
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92 * Exception handlers.
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94 void xPortPendSVHandler( void ) __attribute__ (( naked ));
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95 void xPortSysTickHandler( void );
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96 void vPortSVCHandler( void ) __attribute__ (( naked ));
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99 * Start first task is a separate function so it can be tested in isolation.
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101 void vPortStartFirstTask( void ) __attribute__ (( naked ));
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103 /*-----------------------------------------------------------*/
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106 * See header file for description.
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108 portSTACK_TYPE *pxPortInitialiseStack( portSTACK_TYPE *pxTopOfStack, pdTASK_CODE pxCode, void *pvParameters )
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110 /* Simulate the stack frame as it would be created by a context switch
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112 *pxTopOfStack = portINITIAL_XPSR; /* xPSR */
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114 *pxTopOfStack = ( portSTACK_TYPE ) pxCode; /* PC */
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116 *pxTopOfStack = 0; /* LR */
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117 pxTopOfStack -= 5; /* R12, R3, R2 and R1. */
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118 *pxTopOfStack = ( portSTACK_TYPE ) pvParameters; /* R0 */
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119 pxTopOfStack -= 8; /* R11, R10, R9, R8, R7, R6, R5 and R4. */
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121 return pxTopOfStack;
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123 /*-----------------------------------------------------------*/
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125 void vPortSVCHandler( void )
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128 " ldr r3, pxCurrentTCBConst2 \n" /* Restore the context. */
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129 " ldr r1, [r3] \n" /* Use pxCurrentTCBConst to get the pxCurrentTCB address. */
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130 " ldr r0, [r1] \n" /* The first item in pxCurrentTCB is the task top of stack. */
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131 " ldmia r0!, {r4-r11} \n" /* Pop the registers that are not automatically saved on exception entry and the critical nesting count. */
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132 " msr psp, r0 \n" /* Restore the task stack pointer. */
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134 " msr basepri, r0 \n"
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135 " orr r14, #0xd \n"
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139 "pxCurrentTCBConst2: .word pxCurrentTCB \n"
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142 /*-----------------------------------------------------------*/
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144 void vPortStartFirstTask( void )
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147 " ldr r0, =0xE000ED08 \n" /* Use the NVIC offset register to locate the stack. */
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150 " msr msp, r0 \n" /* Set the msp back to the start of the stack. */
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151 " svc 0 \n" /* System call to start first task. */
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154 /*-----------------------------------------------------------*/
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157 * See header file for description.
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159 portBASE_TYPE xPortStartScheduler( void )
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161 /* Make PendSV, CallSV and SysTick the same priroity as the kernel. */
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162 *(portNVIC_SYSPRI2) |= portNVIC_PENDSV_PRI;
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163 *(portNVIC_SYSPRI2) |= portNVIC_SYSTICK_PRI;
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165 /* Start the timer that generates the tick ISR. Interrupts are disabled
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167 prvSetupTimerInterrupt();
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169 /* Initialise the critical nesting count ready for the first task. */
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170 uxCriticalNesting = 0;
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172 /* Start the first task. */
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173 vPortStartFirstTask();
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175 /* Should not get here! */
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178 /*-----------------------------------------------------------*/
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180 void vPortEndScheduler( void )
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182 /* It is unlikely that the CM3 port will require this function as there
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183 is nothing to return to. */
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185 /*-----------------------------------------------------------*/
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187 void vPortYieldFromISR( void )
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189 /* Set a PendSV to request a context switch. */
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190 *(portNVIC_INT_CTRL) = portNVIC_PENDSVSET;
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192 /*-----------------------------------------------------------*/
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194 void vPortEnterCritical( void )
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196 portDISABLE_INTERRUPTS();
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197 uxCriticalNesting++;
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199 /*-----------------------------------------------------------*/
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201 void vPortExitCritical( void )
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203 uxCriticalNesting--;
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204 if( uxCriticalNesting == 0 )
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206 portENABLE_INTERRUPTS();
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209 /*-----------------------------------------------------------*/
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211 void xPortPendSVHandler( void )
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213 /* This is a naked function. */
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219 " ldr r3, pxCurrentTCBConst \n" /* Get the location of the current TCB. */
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222 " stmdb r0!, {r4-r11} \n" /* Save the remaining registers. */
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223 " str r0, [r2] \n" /* Save the new top of stack into the first member of the TCB. */
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225 " stmdb sp!, {r3, r14} \n"
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227 " msr basepri, r0 \n"
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228 " bl vTaskSwitchContext \n"
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230 " msr basepri, r0 \n"
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231 " ldmia sp!, {r3, r14} \n"
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232 " \n" /* Restore the context, including the critical nesting count. */
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234 " ldr r0, [r1] \n" /* The first item in pxCurrentTCB is the task top of stack. */
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235 " ldmia r0!, {r4-r11} \n" /* Pop the registers. */
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240 "pxCurrentTCBConst: .word pxCurrentTCB \n"
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241 ::"i"(configMAX_SYSCALL_INTERRUPT_PRIORITY)
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244 /*-----------------------------------------------------------*/
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246 void xPortSysTickHandler( void )
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248 unsigned portLONG ulDummy;
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250 /* If using preemption, also force a context switch. */
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251 #if configUSE_PREEMPTION == 1
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252 *(portNVIC_INT_CTRL) = portNVIC_PENDSVSET;
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255 ulDummy = portSET_INTERRUPT_MASK_FROM_ISR();
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257 vTaskIncrementTick();
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259 portCLEAR_INTERRUPT_MASK_FROM_ISR( ulDummy );
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261 /*-----------------------------------------------------------*/
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264 * Setup the systick timer to generate the tick interrupts at the required
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267 void prvSetupTimerInterrupt( void )
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269 /* Configure SysTick to interrupt at the requested rate. */
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270 *(portNVIC_SYSTICK_LOAD) = ( configCPU_CLOCK_HZ / configTICK_RATE_HZ ) - 1UL;
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271 *(portNVIC_SYSTICK_CTRL) = portNVIC_SYSTICK_CLK | portNVIC_SYSTICK_INT | portNVIC_SYSTICK_ENABLE;
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273 /*-----------------------------------------------------------*/
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