2 FreeRTOS V7.5.2 - 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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69 + AVR port - Replaced the inb() and outb() functions with direct memory
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70 access. This allows the port to be built with the 20050414 build of
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75 #include <avr/interrupt.h>
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77 #include "FreeRTOS.h"
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80 /*-----------------------------------------------------------
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81 * Implementation of functions defined in portable.h for the AVR port.
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82 *----------------------------------------------------------*/
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84 /* Start tasks with interrupts enables. */
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85 #define portFLAGS_INT_ENABLED ( ( portSTACK_TYPE ) 0x80 )
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87 /* Hardware constants for timer 1. */
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88 #define portCLEAR_COUNTER_ON_MATCH ( ( unsigned char ) 0x08 )
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89 #define portPRESCALE_64 ( ( unsigned char ) 0x03 )
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90 #define portCLOCK_PRESCALER ( ( unsigned long ) 64 )
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91 #define portCOMPARE_MATCH_A_INTERRUPT_ENABLE ( ( unsigned char ) 0x10 )
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93 /*-----------------------------------------------------------*/
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95 /* We require the address of the pxCurrentTCB variable, but don't want to know
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96 any details of its type. */
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97 typedef void tskTCB;
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98 extern volatile tskTCB * volatile pxCurrentTCB;
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100 /*-----------------------------------------------------------*/
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103 * Macro to save all the general purpose registers, the save the stack pointer
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106 * The first thing we do is save the flags then disable interrupts. This is to
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107 * guard our stack against having a context switch interrupt after we have already
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108 * pushed the registers onto the stack - causing the 32 registers to be on the
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111 * r1 is set to zero as the compiler expects it to be thus, however some
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112 * of the math routines make use of R1.
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114 * The interrupts will have been disabled during the call to portSAVE_CONTEXT()
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115 * so we need not worry about reading/writing to the stack pointer.
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118 #define portSAVE_CONTEXT() \
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119 asm volatile ( "push r0 \n\t" \
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120 "in r0, __SREG__ \n\t" \
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155 "lds r26, pxCurrentTCB \n\t" \
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156 "lds r27, pxCurrentTCB + 1 \n\t" \
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157 "in r0, 0x3d \n\t" \
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159 "in r0, 0x3e \n\t" \
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164 * Opposite to portSAVE_CONTEXT(). Interrupts will have been disabled during
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165 * the context save so we can write to the stack pointer.
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168 #define portRESTORE_CONTEXT() \
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169 asm volatile ( "lds r26, pxCurrentTCB \n\t" \
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170 "lds r27, pxCurrentTCB + 1 \n\t" \
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171 "ld r28, x+ \n\t" \
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172 "out __SP_L__, r28 \n\t" \
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173 "ld r29, x+ \n\t" \
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174 "out __SP_H__, r29 \n\t" \
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207 "out __SREG__, r0 \n\t" \
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211 /*-----------------------------------------------------------*/
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214 * Perform hardware setup to enable ticks from timer 1, compare match A.
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216 static void prvSetupTimerInterrupt( void );
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217 /*-----------------------------------------------------------*/
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220 * See header file for description.
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222 portSTACK_TYPE *pxPortInitialiseStack( portSTACK_TYPE *pxTopOfStack, pdTASK_CODE pxCode, void *pvParameters )
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224 unsigned short usAddress;
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226 /* Place a few bytes of known values on the bottom of the stack.
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227 This is just useful for debugging. */
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229 *pxTopOfStack = 0x11;
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231 *pxTopOfStack = 0x22;
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233 *pxTopOfStack = 0x33;
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236 /* Simulate how the stack would look after a call to vPortYield() generated by
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239 /*lint -e950 -e611 -e923 Lint doesn't like this much - but nothing I can do about it. */
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241 /* The start of the task code will be popped off the stack last, so place
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243 usAddress = ( unsigned short ) pxCode;
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244 *pxTopOfStack = ( portSTACK_TYPE ) ( usAddress & ( unsigned short ) 0x00ff );
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248 *pxTopOfStack = ( portSTACK_TYPE ) ( usAddress & ( unsigned short ) 0x00ff );
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251 /* Next simulate the stack as if after a call to portSAVE_CONTEXT().
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252 portSAVE_CONTEXT places the flags on the stack immediately after r0
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253 to ensure the interrupts get disabled as soon as possible, and so ensuring
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254 the stack use is minimal should a context switch interrupt occur. */
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255 *pxTopOfStack = ( portSTACK_TYPE ) 0x00; /* R0 */
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257 *pxTopOfStack = portFLAGS_INT_ENABLED;
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261 /* Now the remaining registers. The compiler expects R1 to be 0. */
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262 *pxTopOfStack = ( portSTACK_TYPE ) 0x00; /* R1 */
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264 *pxTopOfStack = ( portSTACK_TYPE ) 0x02; /* R2 */
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266 *pxTopOfStack = ( portSTACK_TYPE ) 0x03; /* R3 */
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268 *pxTopOfStack = ( portSTACK_TYPE ) 0x04; /* R4 */
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270 *pxTopOfStack = ( portSTACK_TYPE ) 0x05; /* R5 */
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272 *pxTopOfStack = ( portSTACK_TYPE ) 0x06; /* R6 */
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274 *pxTopOfStack = ( portSTACK_TYPE ) 0x07; /* R7 */
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276 *pxTopOfStack = ( portSTACK_TYPE ) 0x08; /* R8 */
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278 *pxTopOfStack = ( portSTACK_TYPE ) 0x09; /* R9 */
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280 *pxTopOfStack = ( portSTACK_TYPE ) 0x10; /* R10 */
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282 *pxTopOfStack = ( portSTACK_TYPE ) 0x11; /* R11 */
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284 *pxTopOfStack = ( portSTACK_TYPE ) 0x12; /* R12 */
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286 *pxTopOfStack = ( portSTACK_TYPE ) 0x13; /* R13 */
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288 *pxTopOfStack = ( portSTACK_TYPE ) 0x14; /* R14 */
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290 *pxTopOfStack = ( portSTACK_TYPE ) 0x15; /* R15 */
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292 *pxTopOfStack = ( portSTACK_TYPE ) 0x16; /* R16 */
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294 *pxTopOfStack = ( portSTACK_TYPE ) 0x17; /* R17 */
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296 *pxTopOfStack = ( portSTACK_TYPE ) 0x18; /* R18 */
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298 *pxTopOfStack = ( portSTACK_TYPE ) 0x19; /* R19 */
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300 *pxTopOfStack = ( portSTACK_TYPE ) 0x20; /* R20 */
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302 *pxTopOfStack = ( portSTACK_TYPE ) 0x21; /* R21 */
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304 *pxTopOfStack = ( portSTACK_TYPE ) 0x22; /* R22 */
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306 *pxTopOfStack = ( portSTACK_TYPE ) 0x23; /* R23 */
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309 /* Place the parameter on the stack in the expected location. */
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310 usAddress = ( unsigned short ) pvParameters;
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311 *pxTopOfStack = ( portSTACK_TYPE ) ( usAddress & ( unsigned short ) 0x00ff );
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315 *pxTopOfStack = ( portSTACK_TYPE ) ( usAddress & ( unsigned short ) 0x00ff );
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318 *pxTopOfStack = ( portSTACK_TYPE ) 0x26; /* R26 X */
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320 *pxTopOfStack = ( portSTACK_TYPE ) 0x27; /* R27 */
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322 *pxTopOfStack = ( portSTACK_TYPE ) 0x28; /* R28 Y */
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324 *pxTopOfStack = ( portSTACK_TYPE ) 0x29; /* R29 */
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326 *pxTopOfStack = ( portSTACK_TYPE ) 0x30; /* R30 Z */
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328 *pxTopOfStack = ( portSTACK_TYPE ) 0x031; /* R31 */
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331 /*lint +e950 +e611 +e923 */
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333 return pxTopOfStack;
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335 /*-----------------------------------------------------------*/
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337 portBASE_TYPE xPortStartScheduler( void )
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339 /* Setup the hardware to generate the tick. */
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340 prvSetupTimerInterrupt();
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342 /* Restore the context of the first task that is going to run. */
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343 portRESTORE_CONTEXT();
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345 /* Simulate a function call end as generated by the compiler. We will now
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346 jump to the start of the task the context of which we have just restored. */
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347 asm volatile ( "ret" );
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349 /* Should not get here. */
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352 /*-----------------------------------------------------------*/
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354 void vPortEndScheduler( void )
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356 /* It is unlikely that the AVR port will get stopped. If required simply
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357 disable the tick interrupt here. */
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359 /*-----------------------------------------------------------*/
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362 * Manual context switch. The first thing we do is save the registers so we
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363 * can use a naked attribute.
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365 void vPortYield( void ) __attribute__ ( ( naked ) );
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366 void vPortYield( void )
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368 portSAVE_CONTEXT();
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369 vTaskSwitchContext();
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370 portRESTORE_CONTEXT();
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372 asm volatile ( "ret" );
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374 /*-----------------------------------------------------------*/
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377 * Context switch function used by the tick. This must be identical to
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378 * vPortYield() from the call to vTaskSwitchContext() onwards. The only
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379 * difference from vPortYield() is the tick count is incremented as the
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380 * call comes from the tick ISR.
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382 void vPortYieldFromTick( void ) __attribute__ ( ( naked ) );
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383 void vPortYieldFromTick( void )
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385 portSAVE_CONTEXT();
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386 if( xTaskIncrementTick() != pdFALSE )
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388 vTaskSwitchContext();
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390 portRESTORE_CONTEXT();
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392 asm volatile ( "ret" );
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394 /*-----------------------------------------------------------*/
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397 * Setup timer 1 compare match A to generate a tick interrupt.
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399 static void prvSetupTimerInterrupt( void )
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401 unsigned long ulCompareMatch;
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402 unsigned char ucHighByte, ucLowByte;
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404 /* Using 16bit timer 1 to generate the tick. Correct fuses must be
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405 selected for the configCPU_CLOCK_HZ clock. */
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407 ulCompareMatch = configCPU_CLOCK_HZ / configTICK_RATE_HZ;
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409 /* We only have 16 bits so have to scale to get our required tick rate. */
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410 ulCompareMatch /= portCLOCK_PRESCALER;
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412 /* Adjust for correct value. */
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413 ulCompareMatch -= ( unsigned long ) 1;
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415 /* Setup compare match value for compare match A. Interrupts are disabled
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416 before this is called so we need not worry here. */
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417 ucLowByte = ( unsigned char ) ( ulCompareMatch & ( unsigned long ) 0xff );
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418 ulCompareMatch >>= 8;
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419 ucHighByte = ( unsigned char ) ( ulCompareMatch & ( unsigned long ) 0xff );
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420 OCR1AH = ucHighByte;
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421 OCR1AL = ucLowByte;
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423 /* Setup clock source and compare match behaviour. */
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424 ucLowByte = portCLEAR_COUNTER_ON_MATCH | portPRESCALE_64;
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425 TCCR1B = ucLowByte;
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427 /* Enable the interrupt - this is okay as interrupt are currently globally
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430 ucLowByte |= portCOMPARE_MATCH_A_INTERRUPT_ENABLE;
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433 /*-----------------------------------------------------------*/
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435 #if configUSE_PREEMPTION == 1
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438 * Tick ISR for preemptive scheduler. We can use a naked attribute as
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439 * the context is saved at the start of vPortYieldFromTick(). The tick
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440 * count is incremented after the context is saved.
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442 void SIG_OUTPUT_COMPARE1A( void ) __attribute__ ( ( signal, naked ) );
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443 void SIG_OUTPUT_COMPARE1A( void )
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445 vPortYieldFromTick();
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446 asm volatile ( "reti" );
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451 * Tick ISR for the cooperative scheduler. All this does is increment the
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452 * tick count. We don't need to switch context, this can only be done by
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453 * manual calls to taskYIELD();
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455 void SIG_OUTPUT_COMPARE1A( void ) __attribute__ ( ( signal ) );
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456 void SIG_OUTPUT_COMPARE1A( void )
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458 xTaskIncrementTick();
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