2 FreeRTOS V8.2.1 - Copyright (C) 2015 Real Time Engineers Ltd.
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5 VISIT http://www.FreeRTOS.org TO ENSURE YOU ARE USING THE LATEST VERSION.
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7 This file is part of the FreeRTOS distribution.
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9 FreeRTOS is free software; you can redistribute it and/or modify it under
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10 the terms of the GNU General Public License (version 2) as published by the
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11 Free Software Foundation >>!AND MODIFIED BY!<< the FreeRTOS exception.
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13 ***************************************************************************
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14 >>! NOTE: The modification to the GPL is included to allow you to !<<
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15 >>! distribute a combined work that includes FreeRTOS without being !<<
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16 >>! obliged to provide the source code for proprietary components !<<
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17 >>! outside of the FreeRTOS kernel. !<<
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18 ***************************************************************************
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20 FreeRTOS is distributed in the hope that it will be useful, but WITHOUT ANY
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21 WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
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22 FOR A PARTICULAR PURPOSE. Full license text is available on the following
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23 link: http://www.freertos.org/a00114.html
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25 ***************************************************************************
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27 * FreeRTOS provides completely free yet professionally developed, *
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28 * robust, strictly quality controlled, supported, and cross *
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29 * platform software that is more than just the market leader, it *
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30 * is the industry's de facto standard. *
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32 * Help yourself get started quickly while simultaneously helping *
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33 * to support the FreeRTOS project by purchasing a FreeRTOS *
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34 * tutorial book, reference manual, or both: *
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35 * http://www.FreeRTOS.org/Documentation *
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37 ***************************************************************************
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39 http://www.FreeRTOS.org/FAQHelp.html - Having a problem? Start by reading
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40 the FAQ page "My application does not run, what could be wrong?". Have you
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41 defined configASSERT()?
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43 http://www.FreeRTOS.org/support - In return for receiving this top quality
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44 embedded software for free we request you assist our global community by
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45 participating in the support forum.
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47 http://www.FreeRTOS.org/training - Investing in training allows your team to
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48 be as productive as possible as early as possible. Now you can receive
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49 FreeRTOS training directly from Richard Barry, CEO of Real Time Engineers
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50 Ltd, and the world's leading authority on the world's leading RTOS.
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52 http://www.FreeRTOS.org/plus - A selection of FreeRTOS ecosystem products,
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53 including FreeRTOS+Trace - an indispensable productivity tool, a DOS
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54 compatible FAT file system, and our tiny thread aware UDP/IP stack.
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56 http://www.FreeRTOS.org/labs - Where new FreeRTOS products go to incubate.
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57 Come and try FreeRTOS+TCP, our new open source TCP/IP stack for FreeRTOS.
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59 http://www.OpenRTOS.com - Real Time Engineers ltd. license FreeRTOS to High
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60 Integrity Systems ltd. to sell under the OpenRTOS brand. Low cost OpenRTOS
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61 licenses offer ticketed support, indemnification and commercial middleware.
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63 http://www.SafeRTOS.com - High Integrity Systems also provide a safety
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64 engineered and independently SIL3 certified version for use in safety and
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65 mission critical applications that require provable dependability.
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74 + AVR port - Replaced the inb() and outb() functions with direct memory
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75 access. This allows the port to be built with the 20050414 build of
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80 #include <avr/interrupt.h>
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82 #include "FreeRTOS.h"
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85 /*-----------------------------------------------------------
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86 * Implementation of functions defined in portable.h for the AVR port.
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87 *----------------------------------------------------------*/
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89 /* Start tasks with interrupts enables. */
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90 #define portFLAGS_INT_ENABLED ( ( StackType_t ) 0x80 )
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92 /* Hardware constants for timer 1. */
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93 #define portCLEAR_COUNTER_ON_MATCH ( ( uint8_t ) 0x08 )
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94 #define portPRESCALE_64 ( ( uint8_t ) 0x03 )
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95 #define portCLOCK_PRESCALER ( ( uint32_t ) 64 )
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96 #define portCOMPARE_MATCH_A_INTERRUPT_ENABLE ( ( uint8_t ) 0x10 )
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98 /*-----------------------------------------------------------*/
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100 /* We require the address of the pxCurrentTCB variable, but don't want to know
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101 any details of its type. */
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102 typedef void TCB_t;
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103 extern volatile TCB_t * volatile pxCurrentTCB;
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105 /*-----------------------------------------------------------*/
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108 * Macro to save all the general purpose registers, the save the stack pointer
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111 * The first thing we do is save the flags then disable interrupts. This is to
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112 * guard our stack against having a context switch interrupt after we have already
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113 * pushed the registers onto the stack - causing the 32 registers to be on the
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116 * r1 is set to zero as the compiler expects it to be thus, however some
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117 * of the math routines make use of R1.
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119 * The interrupts will have been disabled during the call to portSAVE_CONTEXT()
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120 * so we need not worry about reading/writing to the stack pointer.
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123 #define portSAVE_CONTEXT() \
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124 asm volatile ( "push r0 \n\t" \
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125 "in r0, __SREG__ \n\t" \
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160 "lds r26, pxCurrentTCB \n\t" \
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161 "lds r27, pxCurrentTCB + 1 \n\t" \
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162 "in r0, 0x3d \n\t" \
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164 "in r0, 0x3e \n\t" \
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169 * Opposite to portSAVE_CONTEXT(). Interrupts will have been disabled during
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170 * the context save so we can write to the stack pointer.
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173 #define portRESTORE_CONTEXT() \
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174 asm volatile ( "lds r26, pxCurrentTCB \n\t" \
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175 "lds r27, pxCurrentTCB + 1 \n\t" \
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176 "ld r28, x+ \n\t" \
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177 "out __SP_L__, r28 \n\t" \
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178 "ld r29, x+ \n\t" \
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179 "out __SP_H__, r29 \n\t" \
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212 "out __SREG__, r0 \n\t" \
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216 /*-----------------------------------------------------------*/
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219 * Perform hardware setup to enable ticks from timer 1, compare match A.
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221 static void prvSetupTimerInterrupt( void );
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222 /*-----------------------------------------------------------*/
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225 * See header file for description.
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227 StackType_t *pxPortInitialiseStack( StackType_t *pxTopOfStack, TaskFunction_t pxCode, void *pvParameters )
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229 uint16_t usAddress;
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231 /* Place a few bytes of known values on the bottom of the stack.
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232 This is just useful for debugging. */
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234 *pxTopOfStack = 0x11;
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236 *pxTopOfStack = 0x22;
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238 *pxTopOfStack = 0x33;
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241 /* Simulate how the stack would look after a call to vPortYield() generated by
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244 /*lint -e950 -e611 -e923 Lint doesn't like this much - but nothing I can do about it. */
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246 /* The start of the task code will be popped off the stack last, so place
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248 usAddress = ( uint16_t ) pxCode;
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249 *pxTopOfStack = ( StackType_t ) ( usAddress & ( uint16_t ) 0x00ff );
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253 *pxTopOfStack = ( StackType_t ) ( usAddress & ( uint16_t ) 0x00ff );
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256 /* Next simulate the stack as if after a call to portSAVE_CONTEXT().
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257 portSAVE_CONTEXT places the flags on the stack immediately after r0
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258 to ensure the interrupts get disabled as soon as possible, and so ensuring
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259 the stack use is minimal should a context switch interrupt occur. */
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260 *pxTopOfStack = ( StackType_t ) 0x00; /* R0 */
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262 *pxTopOfStack = portFLAGS_INT_ENABLED;
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266 /* Now the remaining registers. The compiler expects R1 to be 0. */
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267 *pxTopOfStack = ( StackType_t ) 0x00; /* R1 */
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269 *pxTopOfStack = ( StackType_t ) 0x02; /* R2 */
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271 *pxTopOfStack = ( StackType_t ) 0x03; /* R3 */
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273 *pxTopOfStack = ( StackType_t ) 0x04; /* R4 */
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275 *pxTopOfStack = ( StackType_t ) 0x05; /* R5 */
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277 *pxTopOfStack = ( StackType_t ) 0x06; /* R6 */
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279 *pxTopOfStack = ( StackType_t ) 0x07; /* R7 */
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281 *pxTopOfStack = ( StackType_t ) 0x08; /* R8 */
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283 *pxTopOfStack = ( StackType_t ) 0x09; /* R9 */
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285 *pxTopOfStack = ( StackType_t ) 0x10; /* R10 */
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287 *pxTopOfStack = ( StackType_t ) 0x11; /* R11 */
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289 *pxTopOfStack = ( StackType_t ) 0x12; /* R12 */
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291 *pxTopOfStack = ( StackType_t ) 0x13; /* R13 */
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293 *pxTopOfStack = ( StackType_t ) 0x14; /* R14 */
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295 *pxTopOfStack = ( StackType_t ) 0x15; /* R15 */
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297 *pxTopOfStack = ( StackType_t ) 0x16; /* R16 */
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299 *pxTopOfStack = ( StackType_t ) 0x17; /* R17 */
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301 *pxTopOfStack = ( StackType_t ) 0x18; /* R18 */
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303 *pxTopOfStack = ( StackType_t ) 0x19; /* R19 */
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305 *pxTopOfStack = ( StackType_t ) 0x20; /* R20 */
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307 *pxTopOfStack = ( StackType_t ) 0x21; /* R21 */
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309 *pxTopOfStack = ( StackType_t ) 0x22; /* R22 */
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311 *pxTopOfStack = ( StackType_t ) 0x23; /* R23 */
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314 /* Place the parameter on the stack in the expected location. */
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315 usAddress = ( uint16_t ) pvParameters;
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316 *pxTopOfStack = ( StackType_t ) ( usAddress & ( uint16_t ) 0x00ff );
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320 *pxTopOfStack = ( StackType_t ) ( usAddress & ( uint16_t ) 0x00ff );
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323 *pxTopOfStack = ( StackType_t ) 0x26; /* R26 X */
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325 *pxTopOfStack = ( StackType_t ) 0x27; /* R27 */
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327 *pxTopOfStack = ( StackType_t ) 0x28; /* R28 Y */
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329 *pxTopOfStack = ( StackType_t ) 0x29; /* R29 */
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331 *pxTopOfStack = ( StackType_t ) 0x30; /* R30 Z */
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333 *pxTopOfStack = ( StackType_t ) 0x031; /* R31 */
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336 /*lint +e950 +e611 +e923 */
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338 return pxTopOfStack;
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340 /*-----------------------------------------------------------*/
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342 BaseType_t xPortStartScheduler( void )
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344 /* Setup the hardware to generate the tick. */
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345 prvSetupTimerInterrupt();
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347 /* Restore the context of the first task that is going to run. */
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348 portRESTORE_CONTEXT();
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350 /* Simulate a function call end as generated by the compiler. We will now
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351 jump to the start of the task the context of which we have just restored. */
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352 asm volatile ( "ret" );
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354 /* Should not get here. */
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357 /*-----------------------------------------------------------*/
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359 void vPortEndScheduler( void )
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361 /* It is unlikely that the AVR port will get stopped. If required simply
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362 disable the tick interrupt here. */
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364 /*-----------------------------------------------------------*/
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367 * Manual context switch. The first thing we do is save the registers so we
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368 * can use a naked attribute.
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370 void vPortYield( void ) __attribute__ ( ( naked ) );
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371 void vPortYield( void )
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373 portSAVE_CONTEXT();
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374 vTaskSwitchContext();
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375 portRESTORE_CONTEXT();
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377 asm volatile ( "ret" );
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379 /*-----------------------------------------------------------*/
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382 * Context switch function used by the tick. This must be identical to
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383 * vPortYield() from the call to vTaskSwitchContext() onwards. The only
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384 * difference from vPortYield() is the tick count is incremented as the
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385 * call comes from the tick ISR.
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387 void vPortYieldFromTick( void ) __attribute__ ( ( naked ) );
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388 void vPortYieldFromTick( void )
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390 portSAVE_CONTEXT();
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391 if( xTaskIncrementTick() != pdFALSE )
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393 vTaskSwitchContext();
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395 portRESTORE_CONTEXT();
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397 asm volatile ( "ret" );
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399 /*-----------------------------------------------------------*/
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402 * Setup timer 1 compare match A to generate a tick interrupt.
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404 static void prvSetupTimerInterrupt( void )
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406 uint32_t ulCompareMatch;
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407 uint8_t ucHighByte, ucLowByte;
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409 /* Using 16bit timer 1 to generate the tick. Correct fuses must be
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410 selected for the configCPU_CLOCK_HZ clock. */
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412 ulCompareMatch = configCPU_CLOCK_HZ / configTICK_RATE_HZ;
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414 /* We only have 16 bits so have to scale to get our required tick rate. */
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415 ulCompareMatch /= portCLOCK_PRESCALER;
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417 /* Adjust for correct value. */
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418 ulCompareMatch -= ( uint32_t ) 1;
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420 /* Setup compare match value for compare match A. Interrupts are disabled
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421 before this is called so we need not worry here. */
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422 ucLowByte = ( uint8_t ) ( ulCompareMatch & ( uint32_t ) 0xff );
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423 ulCompareMatch >>= 8;
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424 ucHighByte = ( uint8_t ) ( ulCompareMatch & ( uint32_t ) 0xff );
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425 OCR1AH = ucHighByte;
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426 OCR1AL = ucLowByte;
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428 /* Setup clock source and compare match behaviour. */
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429 ucLowByte = portCLEAR_COUNTER_ON_MATCH | portPRESCALE_64;
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430 TCCR1B = ucLowByte;
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432 /* Enable the interrupt - this is okay as interrupt are currently globally
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435 ucLowByte |= portCOMPARE_MATCH_A_INTERRUPT_ENABLE;
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438 /*-----------------------------------------------------------*/
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440 #if configUSE_PREEMPTION == 1
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443 * Tick ISR for preemptive scheduler. We can use a naked attribute as
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444 * the context is saved at the start of vPortYieldFromTick(). The tick
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445 * count is incremented after the context is saved.
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447 void SIG_OUTPUT_COMPARE1A( void ) __attribute__ ( ( signal, naked ) );
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448 void SIG_OUTPUT_COMPARE1A( void )
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450 vPortYieldFromTick();
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451 asm volatile ( "reti" );
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456 * Tick ISR for the cooperative scheduler. All this does is increment the
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457 * tick count. We don't need to switch context, this can only be done by
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458 * manual calls to taskYIELD();
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460 void SIG_OUTPUT_COMPARE1A( void ) __attribute__ ( ( signal ) );
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461 void SIG_OUTPUT_COMPARE1A( void )
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463 xTaskIncrementTick();
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