begriffs open source - cmsis-freertos/blob - Source/portable/ThirdParty/GCC/ATmega/port.c

   1 /*
   2  * FreeRTOS Kernel V10.5.1
   3  * Copyright (C) 2021 Amazon.com, Inc. or its affiliates.  All Rights Reserved.
   4  *
   5  * SPDX-License-Identifier: MIT
   6  *
   7  * Permission is hereby granted, free of charge, to any person obtaining a copy of
   8  * this software and associated documentation files (the "Software"), to deal in
   9  * the Software without restriction, including without limitation the rights to
  10  * use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of
  11  * the Software, and to permit persons to whom the Software is furnished to do so,
  12  * subject to the following conditions:
  13  *
  14  * The above copyright notice and this permission notice shall be included in all
  15  * copies or substantial portions of the Software.
  16  *
  17  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
  18  * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS
  19  * FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR
  20  * COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER
  21  * IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
  22  * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
  23  *
  24  * https://www.FreeRTOS.org
  25  * https://github.com/FreeRTOS
  26  *
  27  */
  28
  29
  30 #include <stdlib.h>
  31
  32 #include <avr/io.h>
  33 #include <avr/interrupt.h>
  34 #include <avr/wdt.h>
  35
  36 #include "FreeRTOS.h"
  37 #include "task.h"
  38
  39 /*-----------------------------------------------------------
  40  * Implementation of functions defined in portable.h for the AVR port.
  41  *----------------------------------------------------------*/
  42
  43 /* Start tasks with interrupts enabled. */
  44 #define portFLAGS_INT_ENABLED           ( (StackType_t) 0x80 )
  45
  46 #if defined( portUSE_WDTO)
  47     #warning "Watchdog Timer used for scheduler."
  48     #define portSCHEDULER_ISR           WDT_vect
  49
  50 #elif defined( portUSE_TIMER0 )
  51 /* Hardware constants for Timer0. */
  52     #warning "Timer0 used for scheduler."
  53     #define portSCHEDULER_ISR           TIMER0_COMPA_vect
  54     #define portCLEAR_COUNTER_ON_MATCH  ( (uint8_t) _BV(WGM01) )
  55     #define portPRESCALE_1024           ( (uint8_t) (_BV(CS02)|_BV(CS00)) )
  56     #define portCLOCK_PRESCALER         ( (uint32_t) 1024 )
  57     #define portCOMPARE_MATCH_A_INTERRUPT_ENABLE    ( (uint8_t) _BV(OCIE0A) )
  58     #define portOCRL                    OCR0A
  59     #define portTCCRa                   TCCR0A
  60     #define portTCCRb                   TCCR0B
  61     #define portTIMSK                   TIMSK0
  62     #define portTIFR                    TIFR0
  63
  64 #else
  65     #error "No Timer defined for scheduler"
  66 #endif
  67
  68 /*-----------------------------------------------------------*/
  69
  70 /* We require the address of the pxCurrentTCB variable, but don't want to know
  71 any details of its type. */
  72 typedef void TCB_t;
  73 extern volatile TCB_t * volatile pxCurrentTCB;
  74
  75 /*-----------------------------------------------------------*/
  76
  77 /**
  78     Enable the watchdog timer, configuring it for expire after
  79     (value) timeout (which is a combination of the WDP0
  80     through WDP3 bits).
  81
  82     This function is derived from <avr/wdt.h> but enables only
  83     the interrupt bit (WDIE), rather than the reset bit (WDE).
  84
  85     Can't find it documented but the WDT, once enabled,
  86     rolls over and fires a new interrupt each time.
  87
  88     See also the symbolic constants WDTO_15MS et al.
  89
  90     Updated to match avr-libc 2.0.0
  91 */
  92
  93 #if defined( portUSE_WDTO)
  94
  95 static __inline__
  96 __attribute__ ((__always_inline__))
  97 void wdt_interrupt_enable (const uint8_t value)
  98 {
  99     if (_SFR_IO_REG_P (_WD_CONTROL_REG))
 100     {
 101         __asm__ __volatile__ (
 102                 "in __tmp_reg__,__SREG__"   "\n\t"
 103                 "cli"                       "\n\t"
 104                 "wdr"                       "\n\t"
 105                 "out %0, %1"                "\n\t"
 106                 "out __SREG__,__tmp_reg__"  "\n\t"
 107                 "out %0, %2"                "\n\t"
 108                 : /* no outputs */
 109                 : "I" (_SFR_IO_ADDR(_WD_CONTROL_REG)),
 110                 "r" ((uint8_t)(_BV(_WD_CHANGE_BIT) | _BV(WDE))),
 111                 "r" ((uint8_t) ((value & 0x08 ? _WD_PS3_MASK : 0x00) |
 112                         _BV(WDIF) | _BV(WDIE) | (value & 0x07)) )
 113                 : "r0"
 114         );
 115     }
 116     else
 117     {
 118         __asm__ __volatile__ (
 119                 "in __tmp_reg__,__SREG__"   "\n\t"
 120                 "cli"                       "\n\t"
 121                 "wdr"                       "\n\t"
 122                 "sts %0, %1"                "\n\t"
 123                 "out __SREG__,__tmp_reg__"  "\n\t"
 124                 "sts %0, %2"                "\n\t"
 125                 : /* no outputs */
 126                 : "n" (_SFR_MEM_ADDR(_WD_CONTROL_REG)),
 127                 "r" ((uint8_t)(_BV(_WD_CHANGE_BIT) | _BV(WDE))),
 128                 "r" ((uint8_t) ((value & 0x08 ? _WD_PS3_MASK : 0x00) |
 129                         _BV(WDIF) | _BV(WDIE) | (value & 0x07)) )
 130                 : "r0"
 131         );
 132     }
 133 }
 134 #endif
 135
 136 /*-----------------------------------------------------------*/
 137 /**
 138     Enable the watchdog timer, configuring it for expire after
 139     (value) timeout (which is a combination of the WDP0
 140     through WDP3 bits).
 141
 142     This function is derived from <avr/wdt.h> but enables both
 143     the reset bit (WDE), and the interrupt bit (WDIE).
 144
 145     This will ensure that if the interrupt is not serviced
 146     before the second timeout, the AVR will reset.
 147
 148     Servicing the interrupt automatically clears it,
 149     and ensures the AVR does not reset.
 150
 151     Can't find it documented but the WDT, once enabled,
 152     rolls over and fires a new interrupt each time.
 153
 154     See also the symbolic constants WDTO_15MS et al.
 155
 156     Updated to match avr-libc 2.0.0
 157 */
 158
 159 #if defined( portUSE_WDTO)
 160
 161 static __inline__
 162 __attribute__ ((__always_inline__))
 163 void wdt_interrupt_reset_enable (const uint8_t value)
 164 {
 165     if (_SFR_IO_REG_P (_WD_CONTROL_REG))
 166     {
 167         __asm__ __volatile__ (
 168                 "in __tmp_reg__,__SREG__"   "\n\t"
 169                 "cli"                       "\n\t"
 170                 "wdr"                       "\n\t"
 171                 "out %0, %1"                "\n\t"
 172                 "out __SREG__,__tmp_reg__"  "\n\t"
 173                 "out %0, %2"                "\n\t"
 174                 : /* no outputs */
 175                 : "I" (_SFR_IO_ADDR(_WD_CONTROL_REG)),
 176                 "r" ((uint8_t)(_BV(_WD_CHANGE_BIT) | _BV(WDE))),
 177                 "r" ((uint8_t) ((value & 0x08 ? _WD_PS3_MASK : 0x00) |
 178                         _BV(WDIF) | _BV(WDIE) | _BV(WDE) | (value & 0x07)) )
 179                 : "r0"
 180         );
 181     }
 182     else
 183     {
 184         __asm__ __volatile__ (
 185                 "in __tmp_reg__,__SREG__"   "\n\t"
 186                 "cli"                       "\n\t"
 187                 "wdr"                       "\n\t"
 188                 "sts %0, %1"                "\n\t"
 189                 "out __SREG__,__tmp_reg__"  "\n\t"
 190                 "sts %0, %2"                "\n\t"
 191                 : /* no outputs */
 192                 : "n" (_SFR_MEM_ADDR(_WD_CONTROL_REG)),
 193                 "r" ((uint8_t)(_BV(_WD_CHANGE_BIT) | _BV(WDE))),
 194                 "r" ((uint8_t) ((value & 0x08 ? _WD_PS3_MASK : 0x00) |
 195                         _BV(WDIF) | _BV(WDIE) | _BV(WDE) | (value & 0x07)) )
 196                 : "r0"
 197         );
 198     }
 199 }
 200 #endif
 201
 202 /*-----------------------------------------------------------*/
 203
 204 /*
 205  * Macro to save all the general purpose registers, the save the stack pointer
 206  * into the TCB.
 207  *
 208  * The first thing we do is save the flags then disable interrupts. This is to
 209  * guard our stack against having a context switch interrupt after we have already
 210  * pushed the registers onto the stack - causing the 32 registers to be on the
 211  * stack twice.
 212  *
 213  * r1 is set to zero (__zero_reg__) as the compiler expects it to be thus, however
 214  * some of the math routines make use of R1.
 215  *
 216  * r0 is set to __tmp_reg__ as the compiler expects it to be thus.
 217  *
 218  * #if defined(__AVR_HAVE_RAMPZ__)
 219  * #define __RAMPZ__ 0x3B
 220  * #endif
 221  *
 222  * #if defined(__AVR_3_BYTE_PC__)
 223  * #define __EIND__ 0x3C
 224  * #endif
 225  *
 226  * The interrupts will have been disabled during the call to portSAVE_CONTEXT()
 227  * so we need not worry about reading/writing to the stack pointer.
 228  */
 229 #if defined(__AVR_3_BYTE_PC__) && defined(__AVR_HAVE_RAMPZ__)
 230 /* 3-Byte PC Save  with RAMPZ */
 231 #define portSAVE_CONTEXT()                                                              \
 232         __asm__ __volatile__ (  "push   __tmp_reg__                             \n\t"   \
 233                                 "in     __tmp_reg__, __SREG__                   \n\t"   \
 234                                 "cli                                            \n\t"   \
 235                                 "push   __tmp_reg__                             \n\t"   \
 236                                 "in     __tmp_reg__, 0x3B                       \n\t"   \
 237                                 "push   __tmp_reg__                             \n\t"   \
 238                                 "in     __tmp_reg__, 0x3C                       \n\t"   \
 239                                 "push   __tmp_reg__                             \n\t"   \
 240                                 "push   __zero_reg__                            \n\t"   \
 241                                 "clr    __zero_reg__                            \n\t"   \
 242                                 "push   r2                                      \n\t"   \
 243                                 "push   r3                                      \n\t"   \
 244                                 "push   r4                                      \n\t"   \
 245                                 "push   r5                                      \n\t"   \
 246                                 "push   r6                                      \n\t"   \
 247                                 "push   r7                                      \n\t"   \
 248                                 "push   r8                                      \n\t"   \
 249                                 "push   r9                                      \n\t"   \
 250                                 "push   r10                                     \n\t"   \
 251                                 "push   r11                                     \n\t"   \
 252                                 "push   r12                                     \n\t"   \
 253                                 "push   r13                                     \n\t"   \
 254                                 "push   r14                                     \n\t"   \
 255                                 "push   r15                                     \n\t"   \
 256                                 "push   r16                                     \n\t"   \
 257                                 "push   r17                                     \n\t"   \
 258                                 "push   r18                                     \n\t"   \
 259                                 "push   r19                                     \n\t"   \
 260                                 "push   r20                                     \n\t"   \
 261                                 "push   r21                                     \n\t"   \
 262                                 "push   r22                                     \n\t"   \
 263                                 "push   r23                                     \n\t"   \
 264                                 "push   r24                                     \n\t"   \
 265                                 "push   r25                                     \n\t"   \
 266                                 "push   r26                                     \n\t"   \
 267                                 "push   r27                                     \n\t"   \
 268                                 "push   r28                                     \n\t"   \
 269                                 "push   r29                                     \n\t"   \
 270                                 "push   r30                                     \n\t"   \
 271                                 "push   r31                                     \n\t"   \
 272                                 "lds    r26, pxCurrentTCB                       \n\t"   \
 273                                 "lds    r27, pxCurrentTCB + 1                   \n\t"   \
 274                                 "in     __tmp_reg__, __SP_L__                   \n\t"   \
 275                                 "st     x+, __tmp_reg__                         \n\t"   \
 276                                 "in     __tmp_reg__, __SP_H__                   \n\t"   \
 277                                 "st     x+, __tmp_reg__                         \n\t"   \
 278                              );
 279 #elif defined(__AVR_HAVE_RAMPZ__)
 280 /* 2-Byte PC Save  with RAMPZ */
 281 #define portSAVE_CONTEXT()                                                              \
 282         __asm__ __volatile__ (  "push   __tmp_reg__                             \n\t"   \
 283                                 "in     __tmp_reg__, __SREG__                   \n\t"   \
 284                                 "cli                                            \n\t"   \
 285                                 "push   __tmp_reg__                             \n\t"   \
 286                                 "in     __tmp_reg__, 0x3B                       \n\t"   \
 287                                 "push   __tmp_reg__                             \n\t"   \
 288                                 "push   __zero_reg__                            \n\t"   \
 289                                 "clr    __zero_reg__                            \n\t"   \
 290                                 "push   r2                                      \n\t"   \
 291                                 "push   r3                                      \n\t"   \
 292                                 "push   r4                                      \n\t"   \
 293                                 "push   r5                                      \n\t"   \
 294                                 "push   r6                                      \n\t"   \
 295                                 "push   r7                                      \n\t"   \
 296                                 "push   r8                                      \n\t"   \
 297                                 "push   r9                                      \n\t"   \
 298                                 "push   r10                                     \n\t"   \
 299                                 "push   r11                                     \n\t"   \
 300                                 "push   r12                                     \n\t"   \
 301                                 "push   r13                                     \n\t"   \
 302                                 "push   r14                                     \n\t"   \
 303                                 "push   r15                                     \n\t"   \
 304                                 "push   r16                                     \n\t"   \
 305                                 "push   r17                                     \n\t"   \
 306                                 "push   r18                                     \n\t"   \
 307                                 "push   r19                                     \n\t"   \
 308                                 "push   r20                                     \n\t"   \
 309                                 "push   r21                                     \n\t"   \
 310                                 "push   r22                                     \n\t"   \
 311                                 "push   r23                                     \n\t"   \
 312                                 "push   r24                                     \n\t"   \
 313                                 "push   r25                                     \n\t"   \
 314                                 "push   r26                                     \n\t"   \
 315                                 "push   r27                                     \n\t"   \
 316                                 "push   r28                                     \n\t"   \
 317                                 "push   r29                                     \n\t"   \
 318                                 "push   r30                                     \n\t"   \
 319                                 "push   r31                                     \n\t"   \
 320                                 "lds    r26, pxCurrentTCB                       \n\t"   \
 321                                 "lds    r27, pxCurrentTCB + 1                   \n\t"   \
 322                                 "in     __tmp_reg__, __SP_L__                   \n\t"   \
 323                                 "st     x+, __tmp_reg__                         \n\t"   \
 324                                 "in     __tmp_reg__, __SP_H__                   \n\t"   \
 325                                 "st     x+, __tmp_reg__                         \n\t"   \
 326                              );
 327 #else
 328 /* 2-Byte PC Save */
 329 #define portSAVE_CONTEXT()                                                              \
 330         __asm__ __volatile__ (  "push   __tmp_reg__                             \n\t"   \
 331                                 "in     __tmp_reg__, __SREG__                   \n\t"   \
 332                                 "cli                                            \n\t"   \
 333                                 "push   __tmp_reg__                             \n\t"   \
 334                                 "push   __zero_reg__                            \n\t"   \
 335                                 "clr    __zero_reg__                            \n\t"   \
 336                                 "push   r2                                      \n\t"   \
 337                                 "push   r3                                      \n\t"   \
 338                                 "push   r4                                      \n\t"   \
 339                                 "push   r5                                      \n\t"   \
 340                                 "push   r6                                      \n\t"   \
 341                                 "push   r7                                      \n\t"   \
 342                                 "push   r8                                      \n\t"   \
 343                                 "push   r9                                      \n\t"   \
 344                                 "push   r10                                     \n\t"   \
 345                                 "push   r11                                     \n\t"   \
 346                                 "push   r12                                     \n\t"   \
 347                                 "push   r13                                     \n\t"   \
 348                                 "push   r14                                     \n\t"   \
 349                                 "push   r15                                     \n\t"   \
 350                                 "push   r16                                     \n\t"   \
 351                                 "push   r17                                     \n\t"   \
 352                                 "push   r18                                     \n\t"   \
 353                                 "push   r19                                     \n\t"   \
 354                                 "push   r20                                     \n\t"   \
 355                                 "push   r21                                     \n\t"   \
 356                                 "push   r22                                     \n\t"   \
 357                                 "push   r23                                     \n\t"   \
 358                                 "push   r24                                     \n\t"   \
 359                                 "push   r25                                     \n\t"   \
 360                                 "push   r26                                     \n\t"   \
 361                                 "push   r27                                     \n\t"   \
 362                                 "push   r28                                     \n\t"   \
 363                                 "push   r29                                     \n\t"   \
 364                                 "push   r30                                     \n\t"   \
 365                                 "push   r31                                     \n\t"   \
 366                                 "lds    r26, pxCurrentTCB                       \n\t"   \
 367                                 "lds    r27, pxCurrentTCB + 1                   \n\t"   \
 368                                 "in     __tmp_reg__, __SP_L__                   \n\t"   \
 369                                 "st     x+, __tmp_reg__                         \n\t"   \
 370                                 "in     __tmp_reg__, __SP_H__                   \n\t"   \
 371                                 "st     x+, __tmp_reg__                         \n\t"   \
 372                              );
 373 #endif
 374
 375 /*
 376  * Opposite to portSAVE_CONTEXT().  Interrupts will have been disabled during
 377  * the context save so we can write to the stack pointer.
 378  */
 379 #if defined(__AVR_3_BYTE_PC__) && defined(__AVR_HAVE_RAMPZ__)
 380 /* 3-Byte PC Restore with RAMPZ */
 381 #define portRESTORE_CONTEXT()                                                           \
 382         __asm__ __volatile__ (  "lds    r26, pxCurrentTCB                       \n\t"   \
 383                                 "lds    r27, pxCurrentTCB + 1                   \n\t"   \
 384                                 "ld     r28, x+                                 \n\t"   \
 385                                 "out    __SP_L__, r28                           \n\t"   \
 386                                 "ld     r29, x+                                 \n\t"   \
 387                                 "out    __SP_H__, r29                           \n\t"   \
 388                                 "pop    r31                                     \n\t"   \
 389                                 "pop    r30                                     \n\t"   \
 390                                 "pop    r29                                     \n\t"   \
 391                                 "pop    r28                                     \n\t"   \
 392                                 "pop    r27                                     \n\t"   \
 393                                 "pop    r26                                     \n\t"   \
 394                                 "pop    r25                                     \n\t"   \
 395                                 "pop    r24                                     \n\t"   \
 396                                 "pop    r23                                     \n\t"   \
 397                                 "pop    r22                                     \n\t"   \
 398                                 "pop    r21                                     \n\t"   \
 399                                 "pop    r20                                     \n\t"   \
 400                                 "pop    r19                                     \n\t"   \
 401                                 "pop    r18                                     \n\t"   \
 402                                 "pop    r17                                     \n\t"   \
 403                                 "pop    r16                                     \n\t"   \
 404                                 "pop    r15                                     \n\t"   \
 405                                 "pop    r14                                     \n\t"   \
 406                                 "pop    r13                                     \n\t"   \
 407                                 "pop    r12                                     \n\t"   \
 408                                 "pop    r11                                     \n\t"   \
 409                                 "pop    r10                                     \n\t"   \
 410                                 "pop    r9                                      \n\t"   \
 411                                 "pop    r8                                      \n\t"   \
 412                                 "pop    r7                                      \n\t"   \
 413                                 "pop    r6                                      \n\t"   \
 414                                 "pop    r5                                      \n\t"   \
 415                                 "pop    r4                                      \n\t"   \
 416                                 "pop    r3                                      \n\t"   \
 417                                 "pop    r2                                      \n\t"   \
 418                                 "pop    __zero_reg__                            \n\t"   \
 419                                 "pop    __tmp_reg__                             \n\t"   \
 420                                 "out    0x3C, __tmp_reg__                       \n\t"   \
 421                                 "pop    __tmp_reg__                             \n\t"   \
 422                                 "out    0x3B, __tmp_reg__                       \n\t"   \
 423                                 "pop    __tmp_reg__                             \n\t"   \
 424                                 "out    __SREG__, __tmp_reg__                   \n\t"   \
 425                                 "pop    __tmp_reg__                             \n\t"   \
 426                              );
 427 #elif defined(__AVR_HAVE_RAMPZ__)
 428 /* 2-Byte PC Restore with RAMPZ */
 429 #define portRESTORE_CONTEXT()                                                           \
 430         __asm__ __volatile__ (  "lds    r26, pxCurrentTCB                       \n\t"   \
 431                                 "lds    r27, pxCurrentTCB + 1                   \n\t"   \
 432                                 "ld     r28, x+                                 \n\t"   \
 433                                 "out    __SP_L__, r28                           \n\t"   \
 434                                 "ld     r29, x+                                 \n\t"   \
 435                                 "out    __SP_H__, r29                           \n\t"   \
 436                                 "pop    r31                                     \n\t"   \
 437                                 "pop    r30                                     \n\t"   \
 438                                 "pop    r29                                     \n\t"   \
 439                                 "pop    r28                                     \n\t"   \
 440                                 "pop    r27                                     \n\t"   \
 441                                 "pop    r26                                     \n\t"   \
 442                                 "pop    r25                                     \n\t"   \
 443                                 "pop    r24                                     \n\t"   \
 444                                 "pop    r23                                     \n\t"   \
 445                                 "pop    r22                                     \n\t"   \
 446                                 "pop    r21                                     \n\t"   \
 447                                 "pop    r20                                     \n\t"   \
 448                                 "pop    r19                                     \n\t"   \
 449                                 "pop    r18                                     \n\t"   \
 450                                 "pop    r17                                     \n\t"   \
 451                                 "pop    r16                                     \n\t"   \
 452                                 "pop    r15                                     \n\t"   \
 453                                 "pop    r14                                     \n\t"   \
 454                                 "pop    r13                                     \n\t"   \
 455                                 "pop    r12                                     \n\t"   \
 456                                 "pop    r11                                     \n\t"   \
 457                                 "pop    r10                                     \n\t"   \
 458                                 "pop    r9                                      \n\t"   \
 459                                 "pop    r8                                      \n\t"   \
 460                                 "pop    r7                                      \n\t"   \
 461                                 "pop    r6                                      \n\t"   \
 462                                 "pop    r5                                      \n\t"   \
 463                                 "pop    r4                                      \n\t"   \
 464                                 "pop    r3                                      \n\t"   \
 465                                 "pop    r2                                      \n\t"   \
 466                                 "pop    __zero_reg__                            \n\t"   \
 467                                 "pop    __tmp_reg__                             \n\t"   \
 468                                 "out    0x3B, __tmp_reg__                       \n\t"   \
 469                                 "pop    __tmp_reg__                             \n\t"   \
 470                                 "out    __SREG__, __tmp_reg__                   \n\t"   \
 471                                 "pop    __tmp_reg__                             \n\t"   \
 472                              );
 473 #else
 474 /* 2-Byte PC Restore */
 475 #define portRESTORE_CONTEXT()                                                           \
 476         __asm__ __volatile__ (  "lds    r26, pxCurrentTCB                       \n\t"   \
 477                                 "lds    r27, pxCurrentTCB + 1                   \n\t"   \
 478                                 "ld     r28, x+                                 \n\t"   \
 479                                 "out    __SP_L__, r28                           \n\t"   \
 480                                 "ld     r29, x+                                 \n\t"   \
 481                                 "out    __SP_H__, r29                           \n\t"   \
 482                                 "pop    r31                                     \n\t"   \
 483                                 "pop    r30                                     \n\t"   \
 484                                 "pop    r29                                     \n\t"   \
 485                                 "pop    r28                                     \n\t"   \
 486                                 "pop    r27                                     \n\t"   \
 487                                 "pop    r26                                     \n\t"   \
 488                                 "pop    r25                                     \n\t"   \
 489                                 "pop    r24                                     \n\t"   \
 490                                 "pop    r23                                     \n\t"   \
 491                                 "pop    r22                                     \n\t"   \
 492                                 "pop    r21                                     \n\t"   \
 493                                 "pop    r20                                     \n\t"   \
 494                                 "pop    r19                                     \n\t"   \
 495                                 "pop    r18                                     \n\t"   \
 496                                 "pop    r17                                     \n\t"   \
 497                                 "pop    r16                                     \n\t"   \
 498                                 "pop    r15                                     \n\t"   \
 499                                 "pop    r14                                     \n\t"   \
 500                                 "pop    r13                                     \n\t"   \
 501                                 "pop    r12                                     \n\t"   \
 502                                 "pop    r11                                     \n\t"   \
 503                                 "pop    r10                                     \n\t"   \
 504                                 "pop    r9                                      \n\t"   \
 505                                 "pop    r8                                      \n\t"   \
 506                                 "pop    r7                                      \n\t"   \
 507                                 "pop    r6                                      \n\t"   \
 508                                 "pop    r5                                      \n\t"   \
 509                                 "pop    r4                                      \n\t"   \
 510                                 "pop    r3                                      \n\t"   \
 511                                 "pop    r2                                      \n\t"   \
 512                                 "pop    __zero_reg__                            \n\t"   \
 513                                 "pop    __tmp_reg__                             \n\t"   \
 514                                 "out    __SREG__, __tmp_reg__                   \n\t"   \
 515                                 "pop    __tmp_reg__                             \n\t"   \
 516                              );
 517 #endif
 518 /*-----------------------------------------------------------*/
 519
 520 /*
 521  * Perform hardware setup to enable ticks from relevant Timer.
 522  */
 523 static void prvSetupTimerInterrupt( void );
 524 /*-----------------------------------------------------------*/
 525
 526 /*
 527  * See header file for description.
 528  */
 529 StackType_t *pxPortInitialiseStack( StackType_t *pxTopOfStack, TaskFunction_t pxCode, void *pvParameters )
 530 {
 531 uint16_t usAddress;
 532     /* Simulate how the stack would look after a call to vPortYield() generated by
 533     the compiler. */
 534
 535     /* The start of the task code will be popped off the stack last, so place
 536     it on first. */
 537     usAddress = ( uint16_t ) pxCode;
 538     *pxTopOfStack = ( StackType_t ) ( usAddress & ( uint16_t ) 0x00ff );
 539     pxTopOfStack--;
 540
 541     usAddress >>= 8;
 542     *pxTopOfStack = ( StackType_t ) ( usAddress & ( uint16_t ) 0x00ff );
 543     pxTopOfStack--;
 544
 545 #if defined(__AVR_3_BYTE_PC__)
 546     /* The AVR ATmega2560/ATmega2561 have 256KBytes of program memory and a 17-bit
 547      * program counter. When a code address is stored on the stack, it takes 3 bytes
 548      * instead of 2 for the other ATmega* chips.
 549      *
 550      * Store 0 as the top byte since we force all task routines to the bottom 128K
 551      * of flash. We do this by using the .lowtext label in the linker script.
 552      *
 553      * In order to do this properly, we would need to get a full 3-byte pointer to
 554      * pxCode. That requires a change to GCC. Not likely to happen any time soon.
 555      */
 556     *pxTopOfStack = 0;
 557     pxTopOfStack--;
 558 #endif
 559
 560     /* Next simulate the stack as if after a call to portSAVE_CONTEXT().
 561     portSAVE_CONTEXT places the flags on the stack immediately after r0
 562     to ensure the interrupts get disabled as soon as possible, and so ensuring
 563     the stack use is minimal should a context switch interrupt occur. */
 564     *pxTopOfStack = ( StackType_t ) 0x00;    /* R0 */
 565     pxTopOfStack--;
 566     *pxTopOfStack = portFLAGS_INT_ENABLED;
 567     pxTopOfStack--;
 568
 569 #if defined(__AVR_3_BYTE_PC__)
 570     /* If we have an ATmega256x, we are also saving the EIND register.
 571      * We should default to 0.
 572      */
 573     *pxTopOfStack = ( StackType_t ) 0x00;    /* EIND */
 574     pxTopOfStack--;
 575 #endif
 576
 577 #if defined(__AVR_HAVE_RAMPZ__)
 578     /* We are saving the RAMPZ register.
 579      * We should default to 0.
 580      */
 581     *pxTopOfStack = ( StackType_t ) 0x00;    /* RAMPZ */
 582     pxTopOfStack--;
 583 #endif
 584
 585     /* Now the remaining registers. The compiler expects R1 to be 0. */
 586     *pxTopOfStack = ( StackType_t ) 0x00;    /* R1 */
 587
 588     /* Leave R2 - R23 untouched */
 589     pxTopOfStack -= 23;
 590
 591     /* Place the parameter on the stack in the expected location. */
 592     usAddress = ( uint16_t ) pvParameters;
 593     *pxTopOfStack = ( StackType_t ) ( usAddress & ( uint16_t ) 0x00ff );
 594     pxTopOfStack--;
 595
 596     usAddress >>= 8;
 597     *pxTopOfStack = ( StackType_t ) ( usAddress & ( uint16_t ) 0x00ff );
 598
 599     /* Leave register R26 - R31 untouched */
 600     pxTopOfStack -= 7;
 601
 602     return pxTopOfStack;
 603 }
 604 /*-----------------------------------------------------------*/
 605
 606 BaseType_t xPortStartScheduler( void )
 607 {
 608     /* Setup the relevant timer hardware to generate the tick. */
 609     prvSetupTimerInterrupt();
 610
 611     /* Restore the context of the first task that is going to run. */
 612     portRESTORE_CONTEXT();
 613
 614     /* Simulate a function call end as generated by the compiler. We will now
 615     jump to the start of the task the context of which we have just restored. */
 616     __asm__ __volatile__ ( "ret" );
 617
 618     /* Should not get here. */
 619     return pdTRUE;
 620 }
 621 /*-----------------------------------------------------------*/
 622
 623 void vPortEndScheduler( void )
 624 {
 625         /* It is unlikely that the ATmega port will get stopped. */
 626 }
 627 /*-----------------------------------------------------------*/
 628
 629 /*
 630  * Manual context switch. The first thing we do is save the registers so we
 631  * can use a naked attribute.
 632  */
 633 void vPortYield( void ) __attribute__ ( ( hot, flatten, naked ) );
 634 void vPortYield( void )
 635 {
 636     portSAVE_CONTEXT();
 637     vTaskSwitchContext();
 638     portRESTORE_CONTEXT();
 639
 640     __asm__ __volatile__ ( "ret" );
 641 }
 642 /*-----------------------------------------------------------*/
 643
 644 /*
 645  * Manual context switch callable from ISRs. The first thing we do is save
 646  * the registers so we can use a naked attribute.
 647  */
 648 void vPortYieldFromISR(void) __attribute__ ( ( hot, flatten, naked ) );
 649 void vPortYieldFromISR(void)
 650 {
 651     portSAVE_CONTEXT();
 652     vTaskSwitchContext();
 653     portRESTORE_CONTEXT();
 654
 655     __asm__ __volatile__ ( "reti" );
 656 }
 657 /*-----------------------------------------------------------*/
 658
 659 /*
 660  * Context switch function used by the tick. This must be identical to
 661  * vPortYield() from the call to vTaskSwitchContext() onwards. The only
 662  * difference from vPortYield() is the tick count is incremented as the
 663  * call comes from the tick ISR.
 664  */
 665 void vPortYieldFromTick( void ) __attribute__ ( ( hot, flatten, naked ) );
 666 void vPortYieldFromTick( void )
 667 {
 668     portSAVE_CONTEXT();
 669     if( xTaskIncrementTick() != pdFALSE )
 670     {
 671         vTaskSwitchContext();
 672     }
 673     portRESTORE_CONTEXT();
 674
 675     __asm__ __volatile__ ( "ret" );
 676 }
 677 /*-----------------------------------------------------------*/
 678
 679 #if defined(portUSE_WDTO)
 680 /*
 681  * Setup WDT to generate a tick interrupt.
 682  */
 683 void prvSetupTimerInterrupt( void )
 684 {
 685     /* reset watchdog */
 686     wdt_reset();
 687
 688     /* set up WDT Interrupt (rather than the WDT Reset). */
 689     wdt_interrupt_enable( portUSE_WDTO );
 690 }
 691
 692 #elif defined (portUSE_TIMER0)
 693 /*
 694  * Setup Timer0 compare match A to generate a tick interrupt.
 695  */
 696 static void prvSetupTimerInterrupt( void )
 697 {
 698 uint32_t ulCompareMatch;
 699 uint8_t ucLowByte;
 700
 701     /* Using 8bit Timer0 to generate the tick. Correct fuses must be
 702     selected for the configCPU_CLOCK_HZ clock.*/
 703
 704     ulCompareMatch = configCPU_CLOCK_HZ / configTICK_RATE_HZ;
 705
 706     /* We only have 8 bits so have to scale 1024 to get our required tick rate. */
 707     ulCompareMatch /= portCLOCK_PRESCALER;
 708
 709     /* Adjust for correct value. */
 710     ulCompareMatch -= ( uint32_t ) 1;
 711
 712     /* Setup compare match value for compare match A. Interrupts are disabled
 713     before this is called so we need not worry here. */
 714     ucLowByte = ( uint8_t ) ( ulCompareMatch & ( uint32_t ) 0xff );
 715     portOCRL = ucLowByte;
 716
 717     /* Setup clock source and compare match behaviour. */
 718     portTCCRa = portCLEAR_COUNTER_ON_MATCH;
 719     portTCCRb = portPRESCALE_1024;
 720
 721
 722     /* Enable the interrupt - this is okay as interrupt are currently globally disabled. */
 723     ucLowByte = portTIMSK;
 724     ucLowByte |= portCOMPARE_MATCH_A_INTERRUPT_ENABLE;
 725     portTIMSK = ucLowByte;
 726 }
 727
 728 #endif
 729
 730 /*-----------------------------------------------------------*/
 731
 732 #if configUSE_PREEMPTION == 1
 733
 734     /*
 735      * Tick ISR for preemptive scheduler. We can use a naked attribute as
 736      * the context is saved at the start of vPortYieldFromTick(). The tick
 737      * count is incremented after the context is saved.
 738      *
 739      * use ISR_NOBLOCK where there is an important timer running, that should preempt the scheduler.
 740      *
 741      */
 742     ISR(portSCHEDULER_ISR, ISR_NAKED) __attribute__ ((hot, flatten));
 743 /*  ISR(portSCHEDULER_ISR, ISR_NAKED ISR_NOBLOCK) __attribute__ ((hot, flatten));
 744  */
 745     ISR(portSCHEDULER_ISR)
 746     {
 747         vPortYieldFromTick();
 748         __asm__ __volatile__ ( "reti" );
 749     }
 750 #else
 751
 752     /*
 753      * Tick ISR for the cooperative scheduler. All this does is increment the
 754      * tick count. We don't need to switch context, this can only be done by
 755      * manual calls to taskYIELD();
 756      *
 757      * use ISR_NOBLOCK where there is an important timer running, that should preempt the scheduler.
 758      */
 759     ISR(portSCHEDULER_ISR) __attribute__ ((hot, flatten));
 760 /*  ISR(portSCHEDULER_ISR, ISR_NOBLOCK) __attribute__ ((hot, flatten));
 761  */
 762     ISR(portSCHEDULER_ISR)
 763     {
 764         xTaskIncrementTick();
 765     }
 766 #endif
 767
 768