2 FreeRTOS V7.5.1 - Copyright (C) 2013 Real Time Engineers Ltd.
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4 VISIT http://www.FreeRTOS.org TO ENSURE YOU ARE USING THE LATEST VERSION.
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6 ***************************************************************************
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8 * FreeRTOS provides completely free yet professionally developed, *
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9 * robust, strictly quality controlled, supported, and cross *
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10 * platform software that has become a de facto standard. *
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12 * Help yourself get started quickly and support the FreeRTOS *
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13 * project by purchasing a FreeRTOS tutorial book, reference *
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14 * manual, or both from: http://www.FreeRTOS.org/Documentation *
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18 ***************************************************************************
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20 This file is part of the FreeRTOS distribution.
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22 FreeRTOS is free software; you can redistribute it and/or modify it under
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23 the terms of the GNU General Public License (version 2) as published by the
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24 Free Software Foundation >>!AND MODIFIED BY!<< the FreeRTOS exception.
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26 >>! NOTE: The modification to the GPL is included to allow you to distribute
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27 >>! a combined work that includes FreeRTOS without being obliged to provide
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28 >>! the source code for proprietary components outside of the FreeRTOS
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31 FreeRTOS is distributed in the hope that it will be useful, but WITHOUT ANY
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32 WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
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33 FOR A PARTICULAR PURPOSE. Full license text is available from the following
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34 link: http://www.freertos.org/a00114.html
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38 ***************************************************************************
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40 * Having a problem? Start by reading the FAQ "My application does *
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41 * not run, what could be wrong?" *
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43 * http://www.FreeRTOS.org/FAQHelp.html *
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45 ***************************************************************************
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47 http://www.FreeRTOS.org - Documentation, books, training, latest versions,
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48 license and Real Time Engineers Ltd. contact details.
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50 http://www.FreeRTOS.org/plus - A selection of FreeRTOS ecosystem products,
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51 including FreeRTOS+Trace - an indispensable productivity tool, a DOS
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52 compatible FAT file system, and our tiny thread aware UDP/IP stack.
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54 http://www.OpenRTOS.com - Real Time Engineers ltd license FreeRTOS to High
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55 Integrity Systems to sell under the OpenRTOS brand. Low cost OpenRTOS
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56 licenses offer ticketed support, indemnification and middleware.
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58 http://www.SafeRTOS.com - High Integrity Systems also provide a safety
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59 engineered and independently SIL3 certified version for use in safety and
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60 mission critical applications that require provable dependability.
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67 #include "FreeRTOS.h"
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70 /*-----------------------------------------------------------
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71 * Implementation of functions defined in portable.h for the AVR/IAR port.
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72 *----------------------------------------------------------*/
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74 /* Start tasks with interrupts enables. */
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75 #define portFLAGS_INT_ENABLED ( ( portSTACK_TYPE ) 0x80 )
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77 /* Hardware constants for timer 1. */
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78 #define portCLEAR_COUNTER_ON_MATCH ( ( unsigned char ) 0x08 )
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79 #define portPRESCALE_64 ( ( unsigned char ) 0x03 )
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80 #define portCLOCK_PRESCALER ( ( unsigned long ) 64 )
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81 #define portCOMPARE_MATCH_A_INTERRUPT_ENABLE ( ( unsigned char ) 0x10 )
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83 /* The number of bytes used on the hardware stack by the task start address. */
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84 #define portBYTES_USED_BY_RETURN_ADDRESS ( 2 )
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85 /*-----------------------------------------------------------*/
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87 /* Stores the critical section nesting. This must not be initialised to 0.
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88 It will be initialised when a task starts. */
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89 #define portNO_CRITICAL_NESTING ( ( unsigned portBASE_TYPE ) 0 )
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90 unsigned portBASE_TYPE uxCriticalNesting = 0x50;
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94 * Perform hardware setup to enable ticks from timer 1, compare match A.
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96 static void prvSetupTimerInterrupt( void );
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99 * The IAR compiler does not have full support for inline assembler, so
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100 * these are defined in the portmacro assembler file.
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102 extern void vPortYieldFromTick( void );
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103 extern void vPortStart( void );
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105 /*-----------------------------------------------------------*/
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108 * See header file for description.
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110 portSTACK_TYPE *pxPortInitialiseStack( portSTACK_TYPE *pxTopOfStack, pdTASK_CODE pxCode, void *pvParameters )
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112 unsigned short usAddress;
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113 portSTACK_TYPE *pxTopOfHardwareStack;
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115 /* Place a few bytes of known values on the bottom of the stack.
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116 This is just useful for debugging. */
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118 *pxTopOfStack = 0x11;
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120 *pxTopOfStack = 0x22;
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122 *pxTopOfStack = 0x33;
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125 /* Remember where the top of the hardware stack is - this is required
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127 pxTopOfHardwareStack = pxTopOfStack;
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130 /* Simulate how the stack would look after a call to vPortYield(). */
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132 /*lint -e950 -e611 -e923 Lint doesn't like this much - but nothing I can do about it. */
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136 /* The IAR compiler requires two stacks per task. First there is the
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137 hardware call stack which uses the AVR stack pointer. Second there is the
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138 software stack (local variables, parameter passing, etc.) which uses the
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141 This function places both stacks within the memory block passed in as the
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142 first parameter. The hardware stack is placed at the bottom of the memory
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143 block. A gap is then left for the hardware stack to grow. Next the software
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144 stack is placed. The amount of space between the software and hardware
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145 stacks is defined by configCALL_STACK_SIZE.
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149 The first part of the stack is the hardware stack. Place the start
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150 address of the task on the hardware stack. */
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151 usAddress = ( unsigned short ) pxCode;
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152 *pxTopOfStack = ( portSTACK_TYPE ) ( usAddress & ( unsigned short ) 0x00ff );
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156 *pxTopOfStack = ( portSTACK_TYPE ) ( usAddress & ( unsigned short ) 0x00ff );
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160 /* Leave enough space for the hardware stack before starting the software
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161 stack. The '- 2' is because we have already used two spaces for the
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162 address of the start of the task. */
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163 pxTopOfStack -= ( configCALL_STACK_SIZE - 2 );
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167 /* Next simulate the stack as if after a call to portSAVE_CONTEXT().
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168 portSAVE_CONTEXT places the flags on the stack immediately after r0
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169 to ensure the interrupts get disabled as soon as possible, and so ensuring
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170 the stack use is minimal should a context switch interrupt occur. */
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171 *pxTopOfStack = ( portSTACK_TYPE ) 0x00; /* R0 */
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173 *pxTopOfStack = portFLAGS_INT_ENABLED;
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176 /* Next place the address of the hardware stack. This is required so
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177 the AVR stack pointer can be restored to point to the hardware stack. */
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178 pxTopOfHardwareStack -= portBYTES_USED_BY_RETURN_ADDRESS;
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179 usAddress = ( unsigned short ) pxTopOfHardwareStack;
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182 *pxTopOfStack = ( portSTACK_TYPE ) ( usAddress & ( unsigned short ) 0x00ff );
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187 *pxTopOfStack = ( portSTACK_TYPE ) ( usAddress & ( unsigned short ) 0x00ff );
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193 /* Now the remaining registers. */
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194 *pxTopOfStack = ( portSTACK_TYPE ) 0x01; /* R1 */
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196 *pxTopOfStack = ( portSTACK_TYPE ) 0x02; /* R2 */
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198 *pxTopOfStack = ( portSTACK_TYPE ) 0x03; /* R3 */
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200 *pxTopOfStack = ( portSTACK_TYPE ) 0x04; /* R4 */
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202 *pxTopOfStack = ( portSTACK_TYPE ) 0x05; /* R5 */
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204 *pxTopOfStack = ( portSTACK_TYPE ) 0x06; /* R6 */
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206 *pxTopOfStack = ( portSTACK_TYPE ) 0x07; /* R7 */
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208 *pxTopOfStack = ( portSTACK_TYPE ) 0x08; /* R8 */
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210 *pxTopOfStack = ( portSTACK_TYPE ) 0x09; /* R9 */
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212 *pxTopOfStack = ( portSTACK_TYPE ) 0x10; /* R10 */
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214 *pxTopOfStack = ( portSTACK_TYPE ) 0x11; /* R11 */
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216 *pxTopOfStack = ( portSTACK_TYPE ) 0x12; /* R12 */
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218 *pxTopOfStack = ( portSTACK_TYPE ) 0x13; /* R13 */
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220 *pxTopOfStack = ( portSTACK_TYPE ) 0x14; /* R14 */
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222 *pxTopOfStack = ( portSTACK_TYPE ) 0x15; /* R15 */
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225 /* Place the parameter on the stack in the expected location. */
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226 usAddress = ( unsigned short ) pvParameters;
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227 *pxTopOfStack = ( portSTACK_TYPE ) ( usAddress & ( unsigned short ) 0x00ff );
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231 *pxTopOfStack = ( portSTACK_TYPE ) ( usAddress & ( unsigned short ) 0x00ff );
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234 *pxTopOfStack = ( portSTACK_TYPE ) 0x18; /* R18 */
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236 *pxTopOfStack = ( portSTACK_TYPE ) 0x19; /* R19 */
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238 *pxTopOfStack = ( portSTACK_TYPE ) 0x20; /* R20 */
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240 *pxTopOfStack = ( portSTACK_TYPE ) 0x21; /* R21 */
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242 *pxTopOfStack = ( portSTACK_TYPE ) 0x22; /* R22 */
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244 *pxTopOfStack = ( portSTACK_TYPE ) 0x23; /* R23 */
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246 *pxTopOfStack = ( portSTACK_TYPE ) 0x24; /* R24 */
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248 *pxTopOfStack = ( portSTACK_TYPE ) 0x25; /* R25 */
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250 *pxTopOfStack = ( portSTACK_TYPE ) 0x26; /* R26 X */
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252 *pxTopOfStack = ( portSTACK_TYPE ) 0x27; /* R27 */
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255 /* The Y register is not stored as it is used as the software stack and
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256 gets saved into the task control block. */
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258 *pxTopOfStack = ( portSTACK_TYPE ) 0x30; /* R30 Z */
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260 *pxTopOfStack = ( portSTACK_TYPE ) 0x031; /* R31 */
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263 *pxTopOfStack = portNO_CRITICAL_NESTING; /* Critical nesting is zero when the task starts. */
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265 /*lint +e950 +e611 +e923 */
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267 return pxTopOfStack;
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269 /*-----------------------------------------------------------*/
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271 portBASE_TYPE xPortStartScheduler( void )
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273 /* Setup the hardware to generate the tick. */
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274 prvSetupTimerInterrupt();
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276 /* Restore the context of the first task that is going to run.
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277 Normally we would just call portRESTORE_CONTEXT() here, but as the IAR
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278 compiler does not fully support inline assembler we have to make a call.*/
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281 /* Should not get here! */
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284 /*-----------------------------------------------------------*/
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286 void vPortEndScheduler( void )
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288 /* It is unlikely that the AVR port will get stopped. If required simply
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289 disable the tick interrupt here. */
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291 /*-----------------------------------------------------------*/
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294 * Setup timer 1 compare match A to generate a tick interrupt.
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296 static void prvSetupTimerInterrupt( void )
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298 unsigned long ulCompareMatch;
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299 unsigned char ucHighByte, ucLowByte;
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301 /* Using 16bit timer 1 to generate the tick. Correct fuses must be
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302 selected for the configCPU_CLOCK_HZ clock. */
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304 ulCompareMatch = configCPU_CLOCK_HZ / configTICK_RATE_HZ;
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306 /* We only have 16 bits so have to scale to get our required tick rate. */
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307 ulCompareMatch /= portCLOCK_PRESCALER;
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309 /* Adjust for correct value. */
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310 ulCompareMatch -= ( unsigned long ) 1;
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312 /* Setup compare match value for compare match A. Interrupts are disabled
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313 before this is called so we need not worry here. */
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314 ucLowByte = ( unsigned char ) ( ulCompareMatch & ( unsigned long ) 0xff );
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315 ulCompareMatch >>= 8;
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316 ucHighByte = ( unsigned char ) ( ulCompareMatch & ( unsigned long ) 0xff );
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317 OCR1AH = ucHighByte;
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318 OCR1AL = ucLowByte;
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320 /* Setup clock source and compare match behaviour. */
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321 ucLowByte = portCLEAR_COUNTER_ON_MATCH | portPRESCALE_64;
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322 TCCR1B = ucLowByte;
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324 /* Enable the interrupt - this is okay as interrupt are currently globally
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326 TIMSK |= portCOMPARE_MATCH_A_INTERRUPT_ENABLE;
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328 /*-----------------------------------------------------------*/
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330 #if configUSE_PREEMPTION == 1
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333 * Tick ISR for preemptive scheduler. We can use a __task attribute as
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334 * the context is saved at the start of vPortYieldFromTick(). The tick
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335 * count is incremented after the context is saved.
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337 __task void SIG_OUTPUT_COMPARE1A( void )
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339 vPortYieldFromTick();
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346 * Tick ISR for the cooperative scheduler. All this does is increment the
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347 * tick count. We don't need to switch context, this can only be done by
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348 * manual calls to taskYIELD();
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350 * THE INTERRUPT VECTOR IS POPULATED IN portmacro.s90. DO NOT INSTALL
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351 * IT HERE USING THE USUAL PRAGMA.
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353 __interrupt void SIG_OUTPUT_COMPARE1A( void )
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355 xTaskIncrementTick();
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358 /*-----------------------------------------------------------*/
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360 void vPortEnterCritical( void )
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362 portDISABLE_INTERRUPTS();
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363 uxCriticalNesting++;
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365 /*-----------------------------------------------------------*/
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367 void vPortExitCritical( void )
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369 uxCriticalNesting--;
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370 if( uxCriticalNesting == portNO_CRITICAL_NESTING )
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372 portENABLE_INTERRUPTS();
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