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

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