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 CM3 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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75 #if configMAX_SYSCALL_INTERRUPT_PRIORITY == 0
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76 #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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79 #ifndef configSYSTICK_CLOCK_HZ
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80 #define configSYSTICK_CLOCK_HZ configCPU_CLOCK_HZ
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81 #if configUSE_TICKLESS_IDLE == 1
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82 static const unsigned long ulStoppedTimerCompensation = 45UL;
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84 #else /* configSYSTICK_CLOCK_HZ */
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85 #if configUSE_TICKLESS_IDLE == 1
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86 /* Assumes the SysTick clock is slower than the CPU clock. */
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87 static const unsigned long ulStoppedTimerCompensation = 45UL / ( configCPU_CLOCK_HZ / configSYSTICK_CLOCK_HZ );
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89 #endif /* configSYSTICK_CLOCK_HZ */
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91 /* Constants required to manipulate the core. Registers first... */
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92 #define portNVIC_SYSTICK_CTRL_REG ( * ( ( volatile unsigned long * ) 0xe000e010 ) )
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93 #define portNVIC_SYSTICK_LOAD_REG ( * ( ( volatile unsigned long * ) 0xe000e014 ) )
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94 #define portNVIC_SYSTICK_CURRENT_VALUE_REG ( * ( ( volatile unsigned long * ) 0xe000e018 ) )
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95 #define portNVIC_INT_CTRL_REG ( * ( ( volatile unsigned long * ) 0xe000ed04 ) )
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96 #define portNVIC_SYSPRI2_REG ( * ( ( volatile unsigned long * ) 0xe000ed20 ) )
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97 /* ...then bits in the registers. */
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98 #define portNVIC_SYSTICK_CLK_BIT ( 1UL << 2UL )
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99 #define portNVIC_SYSTICK_INT_BIT ( 1UL << 1UL )
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100 #define portNVIC_SYSTICK_ENABLE_BIT ( 1UL << 0UL )
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101 #define portNVIC_SYSTICK_COUNT_FLAG_BIT ( 1UL << 16UL )
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102 #define portNVIC_PENDSVSET_BIT ( 1UL << 28UL )
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103 #define portNVIC_PENDSVCLEAR_BIT ( 1UL << 27UL )
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104 #define portNVIC_PEND_SYSTICK_CLEAR_BIT ( 1UL << 25UL )
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106 #define portNVIC_PENDSV_PRI ( ( ( unsigned long ) configKERNEL_INTERRUPT_PRIORITY ) << 16 )
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107 #define portNVIC_SYSTICK_PRI ( ( ( unsigned long ) configKERNEL_INTERRUPT_PRIORITY ) << 24 )
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109 /* Constants required to set up the initial stack. */
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110 #define portINITIAL_XPSR ( 0x01000000 )
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112 /* For backward compatibility, ensure configKERNEL_INTERRUPT_PRIORITY is
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113 defined. The value 255 should also ensure backward compatibility.
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114 FreeRTOS.org versions prior to V4.3.0 did not include this definition. */
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115 #ifndef configKERNEL_INTERRUPT_PRIORITY
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116 #define configKERNEL_INTERRUPT_PRIORITY 0
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119 /* Each task maintains its own interrupt status in the critical nesting
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121 static unsigned portBASE_TYPE uxCriticalNesting = 0xaaaaaaaa;
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124 * Setup the timer to generate the tick interrupts.
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126 static void prvSetupTimerInterrupt( void );
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129 * Exception handlers.
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131 void xPortSysTickHandler( void );
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134 * Start first task is a separate function so it can be tested in isolation.
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136 extern void vPortStartFirstTask( void );
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138 /*-----------------------------------------------------------*/
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141 * The number of SysTick increments that make up one tick period.
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143 static unsigned long ulTimerReloadValueForOneTick = 0;
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146 * The maximum number of tick periods that can be suppressed is limited by the
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147 * 24 bit resolution of the SysTick timer.
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149 #if configUSE_TICKLESS_IDLE == 1
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150 static unsigned long xMaximumPossibleSuppressedTicks = 0;
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151 #endif /* configUSE_TICKLESS_IDLE */
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153 /*-----------------------------------------------------------*/
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156 * See header file for description.
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158 portSTACK_TYPE *pxPortInitialiseStack( portSTACK_TYPE *pxTopOfStack, pdTASK_CODE pxCode, void *pvParameters )
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160 /* Simulate the stack frame as it would be created by a context switch
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162 pxTopOfStack--; /* Offset added to account for the way the MCU uses the stack on entry/exit of interrupts. */
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163 *pxTopOfStack = portINITIAL_XPSR; /* xPSR */
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165 *pxTopOfStack = ( portSTACK_TYPE ) pxCode; /* PC */
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167 *pxTopOfStack = 0; /* LR */
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168 pxTopOfStack -= 5; /* R12, R3, R2 and R1. */
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169 *pxTopOfStack = ( portSTACK_TYPE ) pvParameters; /* R0 */
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170 pxTopOfStack -= 8; /* R11, R10, R9, R8, R7, R6, R5 and R4. */
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172 return pxTopOfStack;
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174 /*-----------------------------------------------------------*/
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177 * See header file for description.
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179 portBASE_TYPE xPortStartScheduler( void )
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181 /* Make PendSV and SysTick the lowest priority interrupts. */
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182 portNVIC_SYSPRI2_REG |= portNVIC_PENDSV_PRI;
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183 portNVIC_SYSPRI2_REG |= portNVIC_SYSTICK_PRI;
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185 /* Start the timer that generates the tick ISR. Interrupts are disabled
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187 prvSetupTimerInterrupt();
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189 /* Initialise the critical nesting count ready for the first task. */
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190 uxCriticalNesting = 0;
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192 /* Start the first task. */
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193 vPortStartFirstTask();
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195 /* Should not get here! */
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198 /*-----------------------------------------------------------*/
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200 void vPortEndScheduler( void )
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202 /* It is unlikely that the CM3 port will require this function as there
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203 is nothing to return to. */
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205 /*-----------------------------------------------------------*/
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207 void vPortYieldFromISR( void )
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209 /* Set a PendSV to request a context switch. */
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210 portNVIC_INT_CTRL_REG = portNVIC_PENDSVSET_BIT;
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212 /*-----------------------------------------------------------*/
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214 void vPortEnterCritical( void )
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216 portDISABLE_INTERRUPTS();
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217 uxCriticalNesting++;
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219 /*-----------------------------------------------------------*/
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221 void vPortExitCritical( void )
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223 uxCriticalNesting--;
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224 if( uxCriticalNesting == 0 )
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226 portENABLE_INTERRUPTS();
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229 /*-----------------------------------------------------------*/
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231 void xPortSysTickHandler( void )
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233 /* If using preemption, also force a context switch. */
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234 #if configUSE_PREEMPTION == 1
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235 portNVIC_INT_CTRL_REG = portNVIC_PENDSVSET_BIT;
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238 #if configUSE_TICKLESS_IDLE == 1
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239 portNVIC_SYSTICK_LOAD_REG = ulTimerReloadValueForOneTick;
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242 ( void ) portSET_INTERRUPT_MASK_FROM_ISR();
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244 vTaskIncrementTick();
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246 portCLEAR_INTERRUPT_MASK_FROM_ISR( 0 );
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248 /*-----------------------------------------------------------*/
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250 #if configUSE_TICKLESS_IDLE == 1
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252 __weak void vPortSuppressTicksAndSleep( portTickType xExpectedIdleTime )
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254 unsigned long ulReloadValue, ulCompleteTickPeriods, ulCompletedSysTickIncrements;
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256 /* Make sure the SysTick reload value does not overflow the counter. */
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257 if( xExpectedIdleTime > xMaximumPossibleSuppressedTicks )
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259 xExpectedIdleTime = xMaximumPossibleSuppressedTicks;
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262 /* Calculate the reload value required to wait xExpectedIdleTime
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263 tick periods. -1 is used because this code will execute part way
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264 through one of the tick periods, and the fraction of a tick period is
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265 accounted for later. */
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266 ulReloadValue = ( ulTimerReloadValueForOneTick * ( xExpectedIdleTime - 1UL ) );
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267 if( ulReloadValue > ulStoppedTimerCompensation )
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269 ulReloadValue -= ulStoppedTimerCompensation;
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272 /* Stop the SysTick momentarily. The time the SysTick is stopped for
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273 is accounted for as best it can be, but using the tickless mode will
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274 inevitably result in some tiny drift of the time maintained by the
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275 kernel with respect to calendar time. */
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276 portNVIC_SYSTICK_CTRL_REG = portNVIC_SYSTICK_CLK_BIT | portNVIC_SYSTICK_INT_BIT;
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278 /* If a context switch is pending then abandon the low power entry as
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279 the context switch might have been pended by an external interrupt that
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280 requires processing. */
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281 if( ( portNVIC_INT_CTRL_REG & portNVIC_PENDSVSET_BIT ) != 0 )
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283 /* Restart SysTick. */
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284 portNVIC_SYSTICK_CTRL_REG = portNVIC_SYSTICK_CLK_BIT | portNVIC_SYSTICK_INT_BIT | portNVIC_SYSTICK_ENABLE_BIT;
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288 /* Adjust the reload value to take into account that the current
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289 time slice is already partially complete. */
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290 ulReloadValue += ( portNVIC_SYSTICK_LOAD_REG - ( portNVIC_SYSTICK_LOAD_REG - portNVIC_SYSTICK_CURRENT_VALUE_REG ) );
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291 portNVIC_SYSTICK_LOAD_REG = ulReloadValue;
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293 /* Clear the SysTick count flag and set the count value back to
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295 portNVIC_SYSTICK_CURRENT_VALUE_REG = 0UL;
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297 /* Restart SysTick. */
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298 portNVIC_SYSTICK_CTRL_REG = portNVIC_SYSTICK_CLK_BIT | portNVIC_SYSTICK_INT_BIT | portNVIC_SYSTICK_ENABLE_BIT;
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300 /* Sleep until something happens. */
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301 portPRE_SLEEP_PROCESSING();
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303 portPOST_SLEEP_PROCESSING();
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305 /* Stop SysTick. Again, the time the SysTick is stopped for is
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306 accounted for as best it can be, but using the tickless mode will
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307 inevitably result in some tiny drift of the time maintained by the
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308 kernel with respect to calendar time. */
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309 portNVIC_SYSTICK_CTRL_REG = portNVIC_SYSTICK_CLK_BIT | portNVIC_SYSTICK_INT_BIT;
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311 if( ( portNVIC_SYSTICK_CTRL_REG & portNVIC_SYSTICK_COUNT_FLAG_BIT ) != 0 )
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313 /* The tick interrupt has already executed, and the SysTick
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314 count reloaded with the portNVIC_SYSTICK_LOAD_REG value.
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315 Reset the portNVIC_SYSTICK_LOAD_REG with whatever remains of
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316 this tick period. */
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317 portNVIC_SYSTICK_LOAD_REG = ulTimerReloadValueForOneTick - ( ulReloadValue - portNVIC_SYSTICK_CURRENT_VALUE_REG );
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319 /* The tick interrupt handler will already have pended the tick
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320 processing in the kernel. As the pending tick will be
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321 processed as soon as this function exits, the tick value
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322 maintained by the tick is stepped forward by one less than the
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323 time spent waiting. */
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324 ulCompleteTickPeriods = xExpectedIdleTime - 1UL;
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328 /* Something other than the tick interrupt ended the sleep.
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329 Work out how long the sleep lasted. */
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330 ulCompletedSysTickIncrements = ( xExpectedIdleTime * ulTimerReloadValueForOneTick ) - portNVIC_SYSTICK_CURRENT_VALUE_REG;
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332 /* How many complete tick periods passed while the processor
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334 ulCompleteTickPeriods = ulCompletedSysTickIncrements / ulTimerReloadValueForOneTick;
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336 /* The reload value is set to whatever fraction of a single tick
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338 portNVIC_SYSTICK_LOAD_REG = ( ( ulCompleteTickPeriods + 1 ) * ulTimerReloadValueForOneTick ) - ulCompletedSysTickIncrements;
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341 /* Restart SysTick so it runs from portNVIC_SYSTICK_LOAD_REG
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342 again, then set portNVIC_SYSTICK_LOAD_REG back to its standard
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344 portNVIC_SYSTICK_CURRENT_VALUE_REG = 0UL;
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345 portNVIC_SYSTICK_CTRL_REG = portNVIC_SYSTICK_CLK_BIT | portNVIC_SYSTICK_INT_BIT | portNVIC_SYSTICK_ENABLE_BIT;
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347 vTaskStepTick( ulCompleteTickPeriods );
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351 #endif /* #if configUSE_TICKLESS_IDLE */
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352 /*-----------------------------------------------------------*/
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355 * Setup the systick timer to generate the tick interrupts at the required
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358 void prvSetupTimerInterrupt( void )
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360 /* Configure the constants required to setup the tick interrupt. */
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361 ulTimerReloadValueForOneTick = ( configSYSTICK_CLOCK_HZ / configTICK_RATE_HZ ) - 1UL;
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362 #if configUSE_TICKLESS_IDLE == 1
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363 xMaximumPossibleSuppressedTicks = 0xffffffUL / ( ( configSYSTICK_CLOCK_HZ / configTICK_RATE_HZ ) - 1UL );
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364 #endif /* configUSE_TICKLESS_IDLE */
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366 /* Configure SysTick to interrupt at the requested rate. */
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367 portNVIC_SYSTICK_LOAD_REG = ulTimerReloadValueForOneTick;
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368 portNVIC_SYSTICK_CTRL_REG = portNVIC_SYSTICK_CLK_BIT | portNVIC_SYSTICK_INT_BIT | portNVIC_SYSTICK_ENABLE_BIT;
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370 /*-----------------------------------------------------------*/
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