2 * FreeRTOS Kernel V10.3.0
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3 * Copyright (C) 2020 Amazon.com, Inc. or its affiliates. All Rights Reserved.
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5 * Permission is hereby granted, free of charge, to any person obtaining a copy of
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6 * this software and associated documentation files (the "Software"), to deal in
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7 * the Software without restriction, including without limitation the rights to
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8 * use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of
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9 * the Software, and to permit persons to whom the Software is furnished to do so,
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10 * subject to the following conditions:
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12 * The above copyright notice and this permission notice shall be included in all
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13 * copies or substantial portions of the Software.
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15 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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16 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS
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17 * FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR
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18 * COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER
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19 * IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
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20 * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
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22 * http://www.FreeRTOS.org
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23 * http://aws.amazon.com/freertos
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25 * 1 tab == 4 spaces!
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32 + AVR port - Replaced the inb() and outb() functions with direct memory
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33 access. This allows the port to be built with the 20050414 build of
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38 #include <avr/interrupt.h>
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40 #include "FreeRTOS.h"
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43 /*-----------------------------------------------------------
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44 * Implementation of functions defined in portable.h for the AVR port.
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45 *----------------------------------------------------------*/
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47 /* Start tasks with interrupts enables. */
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48 #define portFLAGS_INT_ENABLED ( ( StackType_t ) 0x80 )
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50 /* Hardware constants for timer 1. */
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51 #define portCLEAR_COUNTER_ON_MATCH ( ( uint8_t ) 0x08 )
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52 #define portPRESCALE_64 ( ( uint8_t ) 0x03 )
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53 #define portCLOCK_PRESCALER ( ( uint32_t ) 64 )
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54 #define portCOMPARE_MATCH_A_INTERRUPT_ENABLE ( ( uint8_t ) 0x10 )
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56 /*-----------------------------------------------------------*/
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58 /* We require the address of the pxCurrentTCB variable, but don't want to know
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59 any details of its type. */
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61 extern volatile TCB_t * volatile pxCurrentTCB;
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63 /*-----------------------------------------------------------*/
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66 * Macro to save all the general purpose registers, the save the stack pointer
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69 * The first thing we do is save the flags then disable interrupts. This is to
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70 * guard our stack against having a context switch interrupt after we have already
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71 * pushed the registers onto the stack - causing the 32 registers to be on the
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74 * r1 is set to zero as the compiler expects it to be thus, however some
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75 * of the math routines make use of R1.
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77 * The interrupts will have been disabled during the call to portSAVE_CONTEXT()
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78 * so we need not worry about reading/writing to the stack pointer.
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81 #define portSAVE_CONTEXT() \
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82 asm volatile ( "push r0 \n\t" \
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83 "in r0, __SREG__ \n\t" \
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118 "lds r26, pxCurrentTCB \n\t" \
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119 "lds r27, pxCurrentTCB + 1 \n\t" \
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120 "in r0, 0x3d \n\t" \
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122 "in r0, 0x3e \n\t" \
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127 * Opposite to portSAVE_CONTEXT(). Interrupts will have been disabled during
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128 * the context save so we can write to the stack pointer.
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131 #define portRESTORE_CONTEXT() \
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132 asm volatile ( "lds r26, pxCurrentTCB \n\t" \
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133 "lds r27, pxCurrentTCB + 1 \n\t" \
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134 "ld r28, x+ \n\t" \
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135 "out __SP_L__, r28 \n\t" \
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136 "ld r29, x+ \n\t" \
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137 "out __SP_H__, r29 \n\t" \
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170 "out __SREG__, r0 \n\t" \
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174 /*-----------------------------------------------------------*/
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177 * Perform hardware setup to enable ticks from timer 1, compare match A.
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179 static void prvSetupTimerInterrupt( void );
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180 /*-----------------------------------------------------------*/
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183 * See header file for description.
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185 StackType_t *pxPortInitialiseStack( StackType_t *pxTopOfStack, TaskFunction_t pxCode, void *pvParameters )
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187 uint16_t usAddress;
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189 /* Place a few bytes of known values on the bottom of the stack.
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190 This is just useful for debugging. */
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192 *pxTopOfStack = 0x11;
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194 *pxTopOfStack = 0x22;
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196 *pxTopOfStack = 0x33;
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199 /* Simulate how the stack would look after a call to vPortYield() generated by
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202 /*lint -e950 -e611 -e923 Lint doesn't like this much - but nothing I can do about it. */
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204 /* The start of the task code will be popped off the stack last, so place
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206 usAddress = ( uint16_t ) pxCode;
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207 *pxTopOfStack = ( StackType_t ) ( usAddress & ( uint16_t ) 0x00ff );
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211 *pxTopOfStack = ( StackType_t ) ( usAddress & ( uint16_t ) 0x00ff );
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214 /* Next simulate the stack as if after a call to portSAVE_CONTEXT().
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215 portSAVE_CONTEXT places the flags on the stack immediately after r0
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216 to ensure the interrupts get disabled as soon as possible, and so ensuring
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217 the stack use is minimal should a context switch interrupt occur. */
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218 *pxTopOfStack = ( StackType_t ) 0x00; /* R0 */
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220 *pxTopOfStack = portFLAGS_INT_ENABLED;
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224 /* Now the remaining registers. The compiler expects R1 to be 0. */
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225 *pxTopOfStack = ( StackType_t ) 0x00; /* R1 */
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227 *pxTopOfStack = ( StackType_t ) 0x02; /* R2 */
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229 *pxTopOfStack = ( StackType_t ) 0x03; /* R3 */
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231 *pxTopOfStack = ( StackType_t ) 0x04; /* R4 */
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233 *pxTopOfStack = ( StackType_t ) 0x05; /* R5 */
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235 *pxTopOfStack = ( StackType_t ) 0x06; /* R6 */
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237 *pxTopOfStack = ( StackType_t ) 0x07; /* R7 */
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239 *pxTopOfStack = ( StackType_t ) 0x08; /* R8 */
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241 *pxTopOfStack = ( StackType_t ) 0x09; /* R9 */
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243 *pxTopOfStack = ( StackType_t ) 0x10; /* R10 */
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245 *pxTopOfStack = ( StackType_t ) 0x11; /* R11 */
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247 *pxTopOfStack = ( StackType_t ) 0x12; /* R12 */
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249 *pxTopOfStack = ( StackType_t ) 0x13; /* R13 */
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251 *pxTopOfStack = ( StackType_t ) 0x14; /* R14 */
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253 *pxTopOfStack = ( StackType_t ) 0x15; /* R15 */
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255 *pxTopOfStack = ( StackType_t ) 0x16; /* R16 */
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257 *pxTopOfStack = ( StackType_t ) 0x17; /* R17 */
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259 *pxTopOfStack = ( StackType_t ) 0x18; /* R18 */
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261 *pxTopOfStack = ( StackType_t ) 0x19; /* R19 */
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263 *pxTopOfStack = ( StackType_t ) 0x20; /* R20 */
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265 *pxTopOfStack = ( StackType_t ) 0x21; /* R21 */
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267 *pxTopOfStack = ( StackType_t ) 0x22; /* R22 */
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269 *pxTopOfStack = ( StackType_t ) 0x23; /* R23 */
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272 /* Place the parameter on the stack in the expected location. */
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273 usAddress = ( uint16_t ) pvParameters;
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274 *pxTopOfStack = ( StackType_t ) ( usAddress & ( uint16_t ) 0x00ff );
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278 *pxTopOfStack = ( StackType_t ) ( usAddress & ( uint16_t ) 0x00ff );
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281 *pxTopOfStack = ( StackType_t ) 0x26; /* R26 X */
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283 *pxTopOfStack = ( StackType_t ) 0x27; /* R27 */
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285 *pxTopOfStack = ( StackType_t ) 0x28; /* R28 Y */
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287 *pxTopOfStack = ( StackType_t ) 0x29; /* R29 */
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289 *pxTopOfStack = ( StackType_t ) 0x30; /* R30 Z */
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291 *pxTopOfStack = ( StackType_t ) 0x031; /* R31 */
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294 /*lint +e950 +e611 +e923 */
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296 return pxTopOfStack;
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298 /*-----------------------------------------------------------*/
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300 BaseType_t xPortStartScheduler( void )
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302 /* Setup the hardware to generate the tick. */
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303 prvSetupTimerInterrupt();
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305 /* Restore the context of the first task that is going to run. */
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306 portRESTORE_CONTEXT();
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308 /* Simulate a function call end as generated by the compiler. We will now
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309 jump to the start of the task the context of which we have just restored. */
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310 asm volatile ( "ret" );
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312 /* Should not get here. */
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315 /*-----------------------------------------------------------*/
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317 void vPortEndScheduler( void )
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319 /* It is unlikely that the AVR port will get stopped. If required simply
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320 disable the tick interrupt here. */
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322 /*-----------------------------------------------------------*/
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325 * Manual context switch. The first thing we do is save the registers so we
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326 * can use a naked attribute.
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328 void vPortYield( void ) __attribute__ ( ( naked ) );
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329 void vPortYield( void )
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331 portSAVE_CONTEXT();
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332 vTaskSwitchContext();
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333 portRESTORE_CONTEXT();
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335 asm volatile ( "ret" );
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337 /*-----------------------------------------------------------*/
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340 * Context switch function used by the tick. This must be identical to
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341 * vPortYield() from the call to vTaskSwitchContext() onwards. The only
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342 * difference from vPortYield() is the tick count is incremented as the
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343 * call comes from the tick ISR.
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345 void vPortYieldFromTick( void ) __attribute__ ( ( naked ) );
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346 void vPortYieldFromTick( void )
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348 portSAVE_CONTEXT();
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349 if( xTaskIncrementTick() != pdFALSE )
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351 vTaskSwitchContext();
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353 portRESTORE_CONTEXT();
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355 asm volatile ( "ret" );
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357 /*-----------------------------------------------------------*/
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360 * Setup timer 1 compare match A to generate a tick interrupt.
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362 static void prvSetupTimerInterrupt( void )
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364 uint32_t ulCompareMatch;
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365 uint8_t ucHighByte, ucLowByte;
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367 /* Using 16bit timer 1 to generate the tick. Correct fuses must be
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368 selected for the configCPU_CLOCK_HZ clock. */
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370 ulCompareMatch = configCPU_CLOCK_HZ / configTICK_RATE_HZ;
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372 /* We only have 16 bits so have to scale to get our required tick rate. */
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373 ulCompareMatch /= portCLOCK_PRESCALER;
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375 /* Adjust for correct value. */
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376 ulCompareMatch -= ( uint32_t ) 1;
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378 /* Setup compare match value for compare match A. Interrupts are disabled
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379 before this is called so we need not worry here. */
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380 ucLowByte = ( uint8_t ) ( ulCompareMatch & ( uint32_t ) 0xff );
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381 ulCompareMatch >>= 8;
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382 ucHighByte = ( uint8_t ) ( ulCompareMatch & ( uint32_t ) 0xff );
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383 OCR1AH = ucHighByte;
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384 OCR1AL = ucLowByte;
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386 /* Setup clock source and compare match behaviour. */
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387 ucLowByte = portCLEAR_COUNTER_ON_MATCH | portPRESCALE_64;
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388 TCCR1B = ucLowByte;
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390 /* Enable the interrupt - this is okay as interrupt are currently globally
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393 ucLowByte |= portCOMPARE_MATCH_A_INTERRUPT_ENABLE;
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396 /*-----------------------------------------------------------*/
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398 #if configUSE_PREEMPTION == 1
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401 * Tick ISR for preemptive scheduler. We can use a naked attribute as
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402 * the context is saved at the start of vPortYieldFromTick(). The tick
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403 * count is incremented after the context is saved.
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405 void SIG_OUTPUT_COMPARE1A( void ) __attribute__ ( ( signal, naked ) );
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406 void SIG_OUTPUT_COMPARE1A( void )
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408 vPortYieldFromTick();
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409 asm volatile ( "reti" );
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414 * Tick ISR for the cooperative scheduler. All this does is increment the
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415 * tick count. We don't need to switch context, this can only be done by
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416 * manual calls to taskYIELD();
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418 void SIG_OUTPUT_COMPARE1A( void ) __attribute__ ( ( signal ) );
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419 void SIG_OUTPUT_COMPARE1A( void )
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421 xTaskIncrementTick();
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