2 FreeRTOS V7.4.2 - Copyright (C) 2013 Real Time Engineers Ltd.
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4 FEATURES AND PORTS ARE ADDED TO FREERTOS ALL THE TIME. PLEASE VISIT
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5 http://www.FreeRTOS.org TO ENSURE YOU ARE USING THE LATEST VERSION.
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7 ***************************************************************************
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9 * FreeRTOS tutorial books are available in pdf and paperback. *
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10 * Complete, revised, and edited pdf reference manuals are also *
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13 * Purchasing FreeRTOS documentation will not only help you, by *
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14 * ensuring you get running as quickly as possible and with an *
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15 * in-depth knowledge of how to use FreeRTOS, it will also help *
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16 * the FreeRTOS project to continue with its mission of providing *
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17 * professional grade, cross platform, de facto standard solutions *
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18 * for microcontrollers - completely free of charge! *
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20 * >>> See http://www.FreeRTOS.org/Documentation for details. <<< *
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22 * Thank you for using FreeRTOS, and thank you for your support! *
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24 ***************************************************************************
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27 This file is part of the FreeRTOS distribution.
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29 FreeRTOS is free software; you can redistribute it and/or modify it under
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30 the terms of the GNU General Public License (version 2) as published by the
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31 Free Software Foundation AND MODIFIED BY the FreeRTOS exception.
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33 >>>>>>NOTE<<<<<< The modification to the GPL is included to allow you to
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34 distribute a combined work that includes FreeRTOS without being obliged to
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35 provide the source code for proprietary components outside of the FreeRTOS
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38 FreeRTOS is distributed in the hope that it will be useful, but WITHOUT ANY
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39 WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
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40 FOR A PARTICULAR PURPOSE. See the GNU General Public License for more
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41 details. You should have received a copy of the GNU General Public License
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42 and the FreeRTOS license exception along with FreeRTOS; if not it can be
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43 viewed here: http://www.freertos.org/a00114.html and also obtained by
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44 writing to Real Time Engineers Ltd., contact details for whom are available
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45 on the FreeRTOS WEB site.
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49 ***************************************************************************
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51 * Having a problem? Start by reading the FAQ "My application does *
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52 * not run, what could be wrong?" *
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54 * http://www.FreeRTOS.org/FAQHelp.html *
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56 ***************************************************************************
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59 http://www.FreeRTOS.org - Documentation, books, training, latest versions,
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60 license and Real Time Engineers Ltd. contact details.
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62 http://www.FreeRTOS.org/plus - A selection of FreeRTOS ecosystem products,
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63 including FreeRTOS+Trace - an indispensable productivity tool, and our new
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64 fully thread aware and reentrant UDP/IP stack.
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66 http://www.OpenRTOS.com - Real Time Engineers ltd license FreeRTOS to High
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67 Integrity Systems, who sell the code with commercial support,
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68 indemnification and middleware, under the OpenRTOS brand.
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70 http://www.SafeRTOS.com - High Integrity Systems also provide a safety
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71 engineered and independently SIL3 certified version for use in safety and
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72 mission critical applications that require provable dependability.
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79 + AVR port - Replaced the inb() and outb() functions with direct memory
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80 access. This allows the port to be built with the 20050414 build of
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85 #include <avr/interrupt.h>
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87 #include "FreeRTOS.h"
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90 /*-----------------------------------------------------------
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91 * Implementation of functions defined in portable.h for the AVR port.
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92 *----------------------------------------------------------*/
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94 /* Start tasks with interrupts enables. */
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95 #define portFLAGS_INT_ENABLED ( ( portSTACK_TYPE ) 0x80 )
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97 /* Hardware constants for timer 1. */
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98 #define portCLEAR_COUNTER_ON_MATCH ( ( unsigned char ) 0x08 )
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99 #define portPRESCALE_64 ( ( unsigned char ) 0x03 )
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100 #define portCLOCK_PRESCALER ( ( unsigned long ) 64 )
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101 #define portCOMPARE_MATCH_A_INTERRUPT_ENABLE ( ( unsigned char ) 0x10 )
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103 /*-----------------------------------------------------------*/
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105 /* We require the address of the pxCurrentTCB variable, but don't want to know
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106 any details of its type. */
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107 typedef void tskTCB;
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108 extern volatile tskTCB * volatile pxCurrentTCB;
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110 /*-----------------------------------------------------------*/
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113 * Macro to save all the general purpose registers, the save the stack pointer
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116 * The first thing we do is save the flags then disable interrupts. This is to
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117 * guard our stack against having a context switch interrupt after we have already
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118 * pushed the registers onto the stack - causing the 32 registers to be on the
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121 * r1 is set to zero as the compiler expects it to be thus, however some
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122 * of the math routines make use of R1.
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124 * The interrupts will have been disabled during the call to portSAVE_CONTEXT()
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125 * so we need not worry about reading/writing to the stack pointer.
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128 #define portSAVE_CONTEXT() \
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129 asm volatile ( "push r0 \n\t" \
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130 "in r0, __SREG__ \n\t" \
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165 "lds r26, pxCurrentTCB \n\t" \
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166 "lds r27, pxCurrentTCB + 1 \n\t" \
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167 "in r0, 0x3d \n\t" \
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169 "in r0, 0x3e \n\t" \
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174 * Opposite to portSAVE_CONTEXT(). Interrupts will have been disabled during
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175 * the context save so we can write to the stack pointer.
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178 #define portRESTORE_CONTEXT() \
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179 asm volatile ( "lds r26, pxCurrentTCB \n\t" \
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180 "lds r27, pxCurrentTCB + 1 \n\t" \
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181 "ld r28, x+ \n\t" \
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182 "out __SP_L__, r28 \n\t" \
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183 "ld r29, x+ \n\t" \
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184 "out __SP_H__, r29 \n\t" \
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217 "out __SREG__, r0 \n\t" \
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221 /*-----------------------------------------------------------*/
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224 * Perform hardware setup to enable ticks from timer 1, compare match A.
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226 static void prvSetupTimerInterrupt( void );
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227 /*-----------------------------------------------------------*/
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230 * See header file for description.
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232 portSTACK_TYPE *pxPortInitialiseStack( portSTACK_TYPE *pxTopOfStack, pdTASK_CODE pxCode, void *pvParameters )
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234 unsigned short usAddress;
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236 /* Place a few bytes of known values on the bottom of the stack.
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237 This is just useful for debugging. */
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239 *pxTopOfStack = 0x11;
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241 *pxTopOfStack = 0x22;
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243 *pxTopOfStack = 0x33;
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246 /* Simulate how the stack would look after a call to vPortYield() generated by
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249 /*lint -e950 -e611 -e923 Lint doesn't like this much - but nothing I can do about it. */
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251 /* The start of the task code will be popped off the stack last, so place
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253 usAddress = ( unsigned short ) pxCode;
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254 *pxTopOfStack = ( portSTACK_TYPE ) ( usAddress & ( unsigned short ) 0x00ff );
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258 *pxTopOfStack = ( portSTACK_TYPE ) ( usAddress & ( unsigned short ) 0x00ff );
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261 /* Next simulate the stack as if after a call to portSAVE_CONTEXT().
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262 portSAVE_CONTEXT places the flags on the stack immediately after r0
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263 to ensure the interrupts get disabled as soon as possible, and so ensuring
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264 the stack use is minimal should a context switch interrupt occur. */
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265 *pxTopOfStack = ( portSTACK_TYPE ) 0x00; /* R0 */
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267 *pxTopOfStack = portFLAGS_INT_ENABLED;
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271 /* Now the remaining registers. The compiler expects R1 to be 0. */
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272 *pxTopOfStack = ( portSTACK_TYPE ) 0x00; /* R1 */
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274 *pxTopOfStack = ( portSTACK_TYPE ) 0x02; /* R2 */
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276 *pxTopOfStack = ( portSTACK_TYPE ) 0x03; /* R3 */
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278 *pxTopOfStack = ( portSTACK_TYPE ) 0x04; /* R4 */
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280 *pxTopOfStack = ( portSTACK_TYPE ) 0x05; /* R5 */
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282 *pxTopOfStack = ( portSTACK_TYPE ) 0x06; /* R6 */
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284 *pxTopOfStack = ( portSTACK_TYPE ) 0x07; /* R7 */
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286 *pxTopOfStack = ( portSTACK_TYPE ) 0x08; /* R8 */
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288 *pxTopOfStack = ( portSTACK_TYPE ) 0x09; /* R9 */
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290 *pxTopOfStack = ( portSTACK_TYPE ) 0x10; /* R10 */
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292 *pxTopOfStack = ( portSTACK_TYPE ) 0x11; /* R11 */
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294 *pxTopOfStack = ( portSTACK_TYPE ) 0x12; /* R12 */
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296 *pxTopOfStack = ( portSTACK_TYPE ) 0x13; /* R13 */
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298 *pxTopOfStack = ( portSTACK_TYPE ) 0x14; /* R14 */
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300 *pxTopOfStack = ( portSTACK_TYPE ) 0x15; /* R15 */
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302 *pxTopOfStack = ( portSTACK_TYPE ) 0x16; /* R16 */
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304 *pxTopOfStack = ( portSTACK_TYPE ) 0x17; /* R17 */
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306 *pxTopOfStack = ( portSTACK_TYPE ) 0x18; /* R18 */
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308 *pxTopOfStack = ( portSTACK_TYPE ) 0x19; /* R19 */
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310 *pxTopOfStack = ( portSTACK_TYPE ) 0x20; /* R20 */
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312 *pxTopOfStack = ( portSTACK_TYPE ) 0x21; /* R21 */
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314 *pxTopOfStack = ( portSTACK_TYPE ) 0x22; /* R22 */
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316 *pxTopOfStack = ( portSTACK_TYPE ) 0x23; /* R23 */
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319 /* Place the parameter on the stack in the expected location. */
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320 usAddress = ( unsigned short ) pvParameters;
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321 *pxTopOfStack = ( portSTACK_TYPE ) ( usAddress & ( unsigned short ) 0x00ff );
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325 *pxTopOfStack = ( portSTACK_TYPE ) ( usAddress & ( unsigned short ) 0x00ff );
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328 *pxTopOfStack = ( portSTACK_TYPE ) 0x26; /* R26 X */
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330 *pxTopOfStack = ( portSTACK_TYPE ) 0x27; /* R27 */
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332 *pxTopOfStack = ( portSTACK_TYPE ) 0x28; /* R28 Y */
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334 *pxTopOfStack = ( portSTACK_TYPE ) 0x29; /* R29 */
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336 *pxTopOfStack = ( portSTACK_TYPE ) 0x30; /* R30 Z */
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338 *pxTopOfStack = ( portSTACK_TYPE ) 0x031; /* R31 */
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341 /*lint +e950 +e611 +e923 */
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343 return pxTopOfStack;
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345 /*-----------------------------------------------------------*/
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347 portBASE_TYPE xPortStartScheduler( void )
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349 /* Setup the hardware to generate the tick. */
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350 prvSetupTimerInterrupt();
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352 /* Restore the context of the first task that is going to run. */
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353 portRESTORE_CONTEXT();
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355 /* Simulate a function call end as generated by the compiler. We will now
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356 jump to the start of the task the context of which we have just restored. */
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357 asm volatile ( "ret" );
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359 /* Should not get here. */
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362 /*-----------------------------------------------------------*/
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364 void vPortEndScheduler( void )
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366 /* It is unlikely that the AVR port will get stopped. If required simply
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367 disable the tick interrupt here. */
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369 /*-----------------------------------------------------------*/
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372 * Manual context switch. The first thing we do is save the registers so we
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373 * can use a naked attribute.
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375 void vPortYield( void ) __attribute__ ( ( naked ) );
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376 void vPortYield( void )
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378 portSAVE_CONTEXT();
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379 vTaskSwitchContext();
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380 portRESTORE_CONTEXT();
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382 asm volatile ( "ret" );
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384 /*-----------------------------------------------------------*/
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387 * Context switch function used by the tick. This must be identical to
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388 * vPortYield() from the call to vTaskSwitchContext() onwards. The only
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389 * difference from vPortYield() is the tick count is incremented as the
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390 * call comes from the tick ISR.
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392 void vPortYieldFromTick( void ) __attribute__ ( ( naked ) );
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393 void vPortYieldFromTick( void )
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395 portSAVE_CONTEXT();
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396 if( xTaskIncrementTick() != pdFALSE )
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398 vTaskSwitchContext();
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400 portRESTORE_CONTEXT();
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402 asm volatile ( "ret" );
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404 /*-----------------------------------------------------------*/
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407 * Setup timer 1 compare match A to generate a tick interrupt.
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409 static void prvSetupTimerInterrupt( void )
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411 unsigned long ulCompareMatch;
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412 unsigned char ucHighByte, ucLowByte;
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414 /* Using 16bit timer 1 to generate the tick. Correct fuses must be
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415 selected for the configCPU_CLOCK_HZ clock. */
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417 ulCompareMatch = configCPU_CLOCK_HZ / configTICK_RATE_HZ;
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419 /* We only have 16 bits so have to scale to get our required tick rate. */
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420 ulCompareMatch /= portCLOCK_PRESCALER;
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422 /* Adjust for correct value. */
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423 ulCompareMatch -= ( unsigned long ) 1;
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425 /* Setup compare match value for compare match A. Interrupts are disabled
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426 before this is called so we need not worry here. */
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427 ucLowByte = ( unsigned char ) ( ulCompareMatch & ( unsigned long ) 0xff );
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428 ulCompareMatch >>= 8;
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429 ucHighByte = ( unsigned char ) ( ulCompareMatch & ( unsigned long ) 0xff );
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430 OCR1AH = ucHighByte;
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431 OCR1AL = ucLowByte;
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433 /* Setup clock source and compare match behaviour. */
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434 ucLowByte = portCLEAR_COUNTER_ON_MATCH | portPRESCALE_64;
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435 TCCR1B = ucLowByte;
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437 /* Enable the interrupt - this is okay as interrupt are currently globally
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440 ucLowByte |= portCOMPARE_MATCH_A_INTERRUPT_ENABLE;
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443 /*-----------------------------------------------------------*/
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445 #if configUSE_PREEMPTION == 1
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448 * Tick ISR for preemptive scheduler. We can use a naked attribute as
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449 * the context is saved at the start of vPortYieldFromTick(). The tick
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450 * count is incremented after the context is saved.
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452 void SIG_OUTPUT_COMPARE1A( void ) __attribute__ ( ( signal, naked ) );
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453 void SIG_OUTPUT_COMPARE1A( void )
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455 vPortYieldFromTick();
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456 asm volatile ( "reti" );
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461 * Tick ISR for the cooperative scheduler. All this does is increment the
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462 * tick count. We don't need to switch context, this can only be done by
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463 * manual calls to taskYIELD();
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465 void SIG_OUTPUT_COMPARE1A( void ) __attribute__ ( ( signal ) );
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466 void SIG_OUTPUT_COMPARE1A( void )
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468 xTaskIncrementTick();
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