c - MicroC/OS II如何使用定时器的OSTmrCreate实现任务调度？

Question

我在 MicroC 中有 2 个任务来模拟移动的车辆:ControlTask​​ 和 VehicleTask。现在我的项目应该用计时器替换上下文切换以获得更合适的时间，但我似乎无法完成它。该程序现在使用语句 OSTimeDlyHMSM 来实现周期，但软计时器应该与信号量一起使用。 C/OS-II 引用手册(第 16 章)中的 OSTmrCreate。我可以启动一个计时器，然后我可以将它放在开始代码中，但我无法调用计时器并在两个任务之间正确同步，用计时器替换 OSTimeDlyHMSM。我认为我的解决方案变得比必要的更复杂，因为我可能不了解所有细节，例如为什么我需要信号量以及为什么它使用计时器比内置的 OSTimeDlyHMSM 更准确。到目前为止，我的全部工作如下所示:

#include <stdio.h>
#include "system.h"
#include "includes.h"
#include "altera_avalon_pio_regs.h"
#include "sys/alt_irq.h"
#include "sys/alt_alarm.h"

#define DEBUG 1

#define HW_TIMER_PERIOD 100 /* 100ms */

/* Button Patterns */

#define GAS_PEDAL_FLAG      0x08
#define BRAKE_PEDAL_FLAG    0x04
#define CRUISE_CONTROL_FLAG 0x02
/* Switch Patterns */

#define TOP_GEAR_FLAG       0x00000002
#define ENGINE_FLAG         0x00000001

/* LED Patterns */

#define LED_RED_0 0x00000001 // Engine
#define LED_RED_1 0x00000002 // Top Gear

#define LED_GREEN_0 0x0001 // Cruise Control activated
#define LED_GREEN_2 0x0002 // Cruise Control Button
#define LED_GREEN_4 0x0010 // Brake Pedal
#define LED_GREEN_6 0x0040 // Gas Pedal

/*
 * Definition of Tasks
 */

#define TASK_STACKSIZE 2048

OS_STK StartTask_Stack[TASK_STACKSIZE]; 
OS_STK ControlTask_Stack[TASK_STACKSIZE]; 
OS_STK VehicleTask_Stack[TASK_STACKSIZE];

// Task Priorities

#define STARTTASK_PRIO     5
#define VEHICLETASK_PRIO  10
#define CONTROLTASK_PRIO  12

// Task Periods

#define CONTROL_PERIOD  300
#define VEHICLE_PERIOD  300

/*
 * Definition of Kernel Objects 
 */

// Mailboxes
OS_EVENT *Mbox_Throttle;
OS_EVENT *Mbox_Velocity;


// Semaphores
OS_EVENT *aSemaphore;
// SW-Timer
OS_TMR *SWTimer;
OS_TMR *SWTimer1;
BOOLEAN status;
/*
 * Types
 */
enum active {on, off};

enum active gas_pedal = off;
enum active brake_pedal = off;
enum active top_gear = off;
enum active engine = off;
enum active cruise_control = off; 

/*
 * Global variables
 */
int delay; // Delay of HW-timer 
INT16U led_green = 0; // Green LEDs
INT32U led_red = 0;   // Red LEDs

int sharedMemory=1;

void ContextSwitch()
{  
    printf("ContextSwitch!\n"); 
    sharedMemory=sharedMemory*-1;
}
int buttons_pressed(void)
{
  return ~IORD_ALTERA_AVALON_PIO_DATA(DE2_PIO_KEYS4_BASE);    
}

int switches_pressed(void)
{
  return IORD_ALTERA_AVALON_PIO_DATA(DE2_PIO_TOGGLES18_BASE);    
}

/*
 * ISR for HW Timer
 */
alt_u32 alarm_handler(void* context)
{
  OSTmrSignal(); /* Signals a 'tick' to the SW timers */

  return delay;
}

static int b2sLUT[] = {0x40, //0
                 0x79, //1
                 0x24, //2
                 0x30, //3
                 0x19, //4
                 0x12, //5
                 0x02, //6
                 0x78, //7
                 0x00, //8
                 0x18, //9
                 0x3F, //-
};

/*
 * convert int to seven segment display format
 */
int int2seven(int inval){
    return b2sLUT[inval];
}

/*
 * output current velocity on the seven segement display
 */
void show_velocity_on_sevenseg(INT8S velocity){
  int tmp = velocity;
  int out;
  INT8U out_high = 0;
  INT8U out_low = 0;
  INT8U out_sign = 0;

  if(velocity < 0){
     out_sign = int2seven(10);
     tmp *= -1;
  }else{
     out_sign = int2seven(0);
  }

  out_high = int2seven(tmp / 10);
  out_low = int2seven(tmp - (tmp/10) * 10);

  out = int2seven(0) << 21 |
            out_sign << 14 |
            out_high << 7  |
            out_low;
  IOWR_ALTERA_AVALON_PIO_DATA(DE2_PIO_HEX_LOW28_BASE,out);
}

/*
 * shows the target velocity on the seven segment display (HEX5, HEX4)
 * when the cruise control is activated (0 otherwise)
 */
void show_target_velocity(INT8U target_vel)
{
}

/*
 * indicates the position of the vehicle on the track with the four leftmost red LEDs
 * LEDR17: [0m, 400m)
 * LEDR16: [400m, 800m)
 * LEDR15: [800m, 1200m)
 * LEDR14: [1200m, 1600m)
 * LEDR13: [1600m, 2000m)
 * LEDR12: [2000m, 2400m]
 */
void show_position(INT16U position)
{
}

/*
 * The function 'adjust_position()' adjusts the position depending on the
 * acceleration and velocity.
 */
 INT16U adjust_position(INT16U position, INT16S velocity,
                        INT8S acceleration, INT16U time_interval)
{
  INT16S new_position = position + velocity * time_interval / 1000
    + acceleration / 2  * (time_interval / 1000) * (time_interval / 1000);

  if (new_position > 24000) {
    new_position -= 24000;
  } else if (new_position < 0){
    new_position += 24000;
  }

  show_position(new_position);
  return new_position;
}

/*
 * The function 'adjust_velocity()' adjusts the velocity depending on the
 * acceleration.
 */
INT16S adjust_velocity(INT16S velocity, INT8S acceleration,  
               enum active brake_pedal, INT16U time_interval)
{
  INT16S new_velocity;
  INT8U brake_retardation = 200;

  if (brake_pedal == off)
    new_velocity = velocity  + (float) (acceleration * time_interval) / 1000.0;
  else {
    if (brake_retardation * time_interval / 1000 > velocity)
      new_velocity = 0;
    else
      new_velocity = velocity - brake_retardation * time_interval / 1000;
  }

  return new_velocity;
}

/*
 * The task 'VehicleTask' updates the current velocity of the vehicle
 */
void VehicleTask(void* pdata)
{ 
  INT8U err;  
  void* msg;
  INT8U* throttle; 
  INT8S acceleration;  /* Value between 40 and -20 (4.0 m/s^2 and -2.0 m/s^2) */
  INT8S retardation;   /* Value between 20 and -10 (2.0 m/s^2 and -1.0 m/s^2) */
  INT16U position = 0; /* Value between 0 and 20000 (0.0 m and 2000.0 m)  */
  INT16S velocity = 0; /* Value between -200 and 700 (-20.0 m/s amd 70.0 m/s) */
  INT16S wind_factor;   /* Value between -10 and 20 (2.0 m/s^2 and -1.0 m/s^2) */

  printf("Vehicle task created!\n");

  while(1)
    {
      err = OSMboxPost(Mbox_Velocity, (void *) &velocity);

      OSTimeDlyHMSM(0,0,0,VEHICLE_PERIOD); 

      /* Non-blocking read of mailbox: 
       - message in mailbox: update throttle
       - no message:         use old throttle
      */
      msg = OSMboxPend(Mbox_Throttle, 1, &err); 
      if (err == OS_NO_ERR) 
         throttle = (INT8U*) msg;

      /* Retardation : Factor of Terrain and Wind Resistance */
      if (velocity > 0)
         wind_factor = velocity * velocity / 10000 + 1;
      else 
         wind_factor = (-1) * velocity * velocity / 10000 + 1;

      if (position < 4000) 
         retardation = wind_factor; // even ground
      else if (position < 8000)
          retardation = wind_factor + 15; // traveling uphill
        else if (position < 12000)
            retardation = wind_factor + 25; // traveling steep uphill
          else if (position < 16000)
              retardation = wind_factor; // even ground
            else if (position < 20000)
                retardation = wind_factor - 10; //traveling downhill
              else
                  retardation = wind_factor - 5 ; // traveling steep downhill

      acceleration = *throttle / 2 - retardation;     
      position = adjust_position(position, velocity, acceleration, 300); 
      velocity = adjust_velocity(velocity, acceleration, brake_pedal, 300); 
      printf("Position: %dm\n", position / 10);
      printf("Velocity: %4.1fm/s\n", velocity /10.0);
      printf("Throttle: %dV\n", *throttle / 10);
      show_velocity_on_sevenseg((INT8S) (velocity / 10));
    }
} 

/*
 * The task 'ControlTask' is the main task of the application. It reacts
 * on sensors and generates responses.
 */

void ControlTask(void* pdata)
{
  INT8U err;
  INT8U throttle = 40; /* Value between 0 and 80, which is interpreted as between 0.0V and 8.0V */
  void* msg;
  INT16S* current_velocity;

  printf("Control Task created!\n");

  while(1)
    {
      msg = OSMboxPend(Mbox_Velocity, 0, &err);
      current_velocity = (INT16S*) msg;

      err = OSMboxPost(Mbox_Throttle, (void *) &throttle);

      OSTimeDlyHMSM(0,0,0, CONTROL_PERIOD);
    }
}

/* 
 * The task 'StartTask' creates all other tasks kernel objects and
 * deletes itself afterwards.
 */ 

void StartTask(void* pdata)
{
  INT8U err;
  void* context;

  static alt_alarm alarm;     /* Is needed for timer ISR function */

  /* Base resolution for SW timer : HW_TIMER_PERIOD ms */
  delay = alt_ticks_per_second() * HW_TIMER_PERIOD / 1000; 
  printf("delay in ticks %d\n", delay);

  /* 
   * Create Hardware Timer with a period of 'delay' 
   */
  if (alt_alarm_start (&alarm,
      delay,
      alarm_handler,
      context) < 0)
      {
          printf("No system clock available!n");
      }

  /* 
   * Create and start Software Timer 
   */

  SWTimer = OSTmrCreate(0,
  CONTROL_PERIOD/(4*OS_TMR_CFG_TICKS_PER_SEC),
  OS_TMR_OPT_PERIODIC,
  ContextSwitch,
  NULL,
  NULL,
  &err);
     if (err == OS_ERR_NONE) {
  /* Timer was created but NOT started */
  printf("SWTimer was created but NOT started \n");
  }

  status = OSTmrStart(SWTimer,
    &err);
  if (err == OS_ERR_NONE) {
  /* Timer was started */
    printf("SWTimer was started!\n");
  }
  /*
   * Creation of Kernel Objects
   */

  // Mailboxes
  Mbox_Throttle = OSMboxCreate((void*) 0); /* Empty Mailbox - Throttle */
  Mbox_Velocity = OSMboxCreate((void*) 0); /* Empty Mailbox - Velocity */

  /*
   * Create statistics task
   */

  OSStatInit();

  /* 
   * Creating Tasks in the system 
   */


  err = OSTaskCreateExt(
       ControlTask, // Pointer to task code
       NULL,        // Pointer to argument that is
                    // passed to task
       &ControlTask_Stack[TASK_STACKSIZE-1], // Pointer to top
                             // of task stack
       CONTROLTASK_PRIO,
       CONTROLTASK_PRIO,
       (void *)&ControlTask_Stack[0],
       TASK_STACKSIZE,
       (void *) 0,
       OS_TASK_OPT_STK_CHK);

  err = OSTaskCreateExt(
       VehicleTask, // Pointer to task code
       NULL,        // Pointer to argument that is
                    // passed to task
       &VehicleTask_Stack[TASK_STACKSIZE-1], // Pointer to top
                             // of task stack
       VEHICLETASK_PRIO,
       VEHICLETASK_PRIO,
       (void *)&VehicleTask_Stack[0],
       TASK_STACKSIZE,
       (void *) 0,
       OS_TASK_OPT_STK_CHK);

  printf("All Tasks and Kernel Objects generated!\n");

  /* Task deletes itself */

  OSTaskDel(OS_PRIO_SELF);
}

/*
 *
 * The function 'main' creates only a single task 'StartTask' and starts
 * the OS. All other tasks are started from the task 'StartTask'.
 *
 */

int main(void) {

  printf("Cruise Control\n");
  aSemaphore = OSSemCreate(1); // binary semaphore (1 key)  

  OSTaskCreateExt(
     StartTask, // Pointer to task code
         NULL,      // Pointer to argument that is
                    // passed to task
         (void *)&StartTask_Stack[TASK_STACKSIZE-1], // Pointer to top
                             // of task stack 
         STARTTASK_PRIO,
         STARTTASK_PRIO,
         (void *)&StartTask_Stack[0],
         TASK_STACKSIZE,
         (void *) 0,  
         OS_TASK_OPT_STK_CHK | OS_TASK_OPT_STK_CLR);

  OSStart();

  return 0;
}

运行上面的程序，回调 contextswitch 被执行，但它还没有解决使用定时器而不是内置 yield 的问题以及如何将它与信号量一起应用。

Cruise Control
delay in ticks 100
SWTimer was created but NOT started 
SWTimer was started!
All Tasks and Kernel Objects generated!
Vehicle task created!
Control Task created!
ContextSwitch!
Position: 0m
Velocity:  0.5m/s
Throttle: 4V
ContextSwitch!
Position: 0m
Velocity:  1.0m/s
Throttle: 4V
Position: 0m
Velocity:  1.5m/s
Throttle: 4V
ContextSwitch!
Position: 0m
Velocity:  2.0m/s
Throttle: 4V
ContextSwitch!
Position: 1m
Velocity:  2.5m/s
Throttle: 4V
ContextSwitch!
Position: 2m
Velocity:  3.0m/s
Throttle: 4V
ContextSwitch!

更新 141001 15:57 CET

2 个信号量 + 2 个计时器似乎是一个很好的改进。我希望它可以检查或测试...

#include <stdio.h>
#include "system.h"
#include "includes.h"
#include "altera_avalon_pio_regs.h"
#include "sys/alt_irq.h"
#include "sys/alt_alarm.h"

#define DEBUG 1

#define HW_TIMER_PERIOD 100 /* 100ms */

/* Button Patterns */

#define GAS_PEDAL_FLAG      0x08
#define BRAKE_PEDAL_FLAG    0x04
#define CRUISE_CONTROL_FLAG 0x02
/* Switch Patterns */

#define TOP_GEAR_FLAG       0x00000002
#define ENGINE_FLAG         0x00000001

/* LED Patterns */

#define LED_RED_0 0x00000001 // Engine
#define LED_RED_1 0x00000002 // Top Gear

#define LED_GREEN_0 0x0001 // Cruise Control activated
#define LED_GREEN_2 0x0002 // Cruise Control Button
#define LED_GREEN_4 0x0010 // Brake Pedal
#define LED_GREEN_6 0x0040 // Gas Pedal

/*
 * Definition of Tasks
 */

#define TASK_STACKSIZE 2048

OS_STK StartTask_Stack[TASK_STACKSIZE]; 
OS_STK ControlTask_Stack[TASK_STACKSIZE]; 
OS_STK VehicleTask_Stack[TASK_STACKSIZE];

// Task Priorities

#define STARTTASK_PRIO     5
#define VEHICLETASK_PRIO  10
#define CONTROLTASK_PRIO  12

// Task Periods

#define CONTROL_PERIOD  300
#define VEHICLE_PERIOD  300

/*
 * Definition of Kernel Objects 
 */

// Mailboxes
OS_EVENT *Mbox_Throttle;
OS_EVENT *Mbox_Velocity;


// Semaphores
OS_EVENT *aSemaphore;
OS_EVENT *aSemaphore2;
// SW-Timer
OS_TMR *SWTimer;
OS_TMR *SWTimer1;
BOOLEAN status;
/*
 * Types
 */
enum active {on, off};

enum active gas_pedal = off;
enum active brake_pedal = off;
enum active top_gear = off;
enum active engine = off;
enum active cruise_control = off; 

/*
 * Global variables
 */
int delay; // Delay of HW-timer 
INT16U led_green = 0; // Green LEDs
INT32U led_red = 0;   // Red LEDs

int sharedMemory=1;
void TimerCallback(params)
{
    // Post to the semaphore to signal that it's time to run the task.
    OSSemPost(aSemaphore); // Releasing the key
}
void ContextSwitch()
{  
    printf("ContextSwitch!\n"); 
    sharedMemory=sharedMemory*-1;
}
int buttons_pressed(void)
{
  return ~IORD_ALTERA_AVALON_PIO_DATA(DE2_PIO_KEYS4_BASE);    
}

int switches_pressed(void)
{
  return IORD_ALTERA_AVALON_PIO_DATA(DE2_PIO_TOGGLES18_BASE);    
}

/*
 * ISR for HW Timer
 */
alt_u32 alarm_handler(void* context)
{
  OSTmrSignal(); /* Signals a 'tick' to the SW timers */

  return delay;
}

void release()
{
  printf("release key!\n");
  //OSSemPost(aSemaphore); // Releasing the key
  OSSemPost(aSemaphore2); // Releasing the key
  printf("released key!\n");
}
void release2()
{
  printf("release2!\n");
  OSSemPost(aSemaphore2); // Releasing the key
  printf("release2!\n");
}

static int b2sLUT[] = {0x40, //0
                 0x79, //1
                 0x24, //2
                 0x30, //3
                 0x19, //4
                 0x12, //5
                 0x02, //6
                 0x78, //7
                 0x00, //8
                 0x18, //9
                 0x3F, //-
};

/*
 * convert int to seven segment display format
 */
int int2seven(int inval){
    return b2sLUT[inval];
}

/*
 * output current velocity on the seven segement display
 */
void show_velocity_on_sevenseg(INT8S velocity){
  int tmp = velocity;
  int out;
  INT8U out_high = 0;
  INT8U out_low = 0;
  INT8U out_sign = 0;

  if(velocity < 0){
     out_sign = int2seven(10);
     tmp *= -1;
  }else{
     out_sign = int2seven(0);
  }

  out_high = int2seven(tmp / 10);
  out_low = int2seven(tmp - (tmp/10) * 10);

  out = int2seven(0) << 21 |
            out_sign << 14 |
            out_high << 7  |
            out_low;
  IOWR_ALTERA_AVALON_PIO_DATA(DE2_PIO_HEX_LOW28_BASE,out);
}

/*
 * shows the target velocity on the seven segment display (HEX5, HEX4)
 * when the cruise control is activated (0 otherwise)
 */
void show_target_velocity(INT8U target_vel)
{
}

/*
 * indicates the position of the vehicle on the track with the four leftmost red LEDs
 * LEDR17: [0m, 400m)
 * LEDR16: [400m, 800m)
 * LEDR15: [800m, 1200m)
 * LEDR14: [1200m, 1600m)
 * LEDR13: [1600m, 2000m)
 * LEDR12: [2000m, 2400m]
 */
void show_position(INT16U position)
{
}

/*
 * The function 'adjust_position()' adjusts the position depending on the
 * acceleration and velocity.
 */
 INT16U adjust_position(INT16U position, INT16S velocity,
                        INT8S acceleration, INT16U time_interval)
{
  INT16S new_position = position + velocity * time_interval / 1000
    + acceleration / 2  * (time_interval / 1000) * (time_interval / 1000);

  if (new_position > 24000) {
    new_position -= 24000;
  } else if (new_position < 0){
    new_position += 24000;
  }

  show_position(new_position);
  return new_position;
}

/*
 * The function 'adjust_velocity()' adjusts the velocity depending on the
 * acceleration.
 */
INT16S adjust_velocity(INT16S velocity, INT8S acceleration,  
               enum active brake_pedal, INT16U time_interval)
{
  INT16S new_velocity;
  INT8U brake_retardation = 200;

  if (brake_pedal == off)
    new_velocity = velocity  + (float) (acceleration * time_interval) / 1000.0;
  else {
    if (brake_retardation * time_interval / 1000 > velocity)
      new_velocity = 0;
    else
      new_velocity = velocity - brake_retardation * time_interval / 1000;
  }

  return new_velocity;
}

/*
 * The task 'VehicleTask' updates the current velocity of the vehicle
 */
void VehicleTask(void* pdata)
{ 
  INT8U err;  
  void* msg;
  INT8U* throttle; 
  INT8S acceleration;  /* Value between 40 and -20 (4.0 m/s^2 and -2.0 m/s^2) */
  INT8S retardation;   /* Value between 20 and -10 (2.0 m/s^2 and -1.0 m/s^2) */
  INT16U position = 0; /* Value between 0 and 20000 (0.0 m and 2000.0 m)  */
  INT16S velocity = 0; /* Value between -200 and 700 (-20.0 m/s amd 70.0 m/s) */
  INT16S wind_factor;   /* Value between -10 and 20 (2.0 m/s^2 and -1.0 m/s^2) */

  printf("Vehicle task created!\n");
// Create a semaphore to represent the "it's time to run" event.
    // Initialize the semaphore count to zero because it's not time
    // to run yet.

    // Create a periodic software timer which calls TimerCallback()
    // when it expires.

    /* 
   * Create and start Software Timer 
   */

  SWTimer1 = OSTmrCreate(0,
  CONTROL_PERIOD/(4*OS_TMR_CFG_TICKS_PER_SEC),
  OS_TMR_OPT_PERIODIC,
  TimerCallback,
  NULL,
  NULL,
  &err);
     if (err == OS_ERR_NONE) {
  /* Timer was created but NOT started */
  printf("SWTimer1 was created but NOT started \n");
  }

  status = OSTmrStart(SWTimer1,
    &err);
  if (err == OS_ERR_NONE) {
  /* Timer was started */
    printf("SWTimer1 was started!\n");
  }

  while(1)
    {
      OSSemPend(aSemaphore, 0, &err); // Trying to access the key   
      err = OSMboxPost(Mbox_Velocity, (void *) &velocity);

      //OSTimeDlyHMSM(0,0,0,VEHICLE_PERIOD); 

      /* Non-blocking read of mailbox: 
       - message in mailbox: update throttle
       - no message:         use old throttle
      */
      msg = OSMboxPend(Mbox_Throttle, 1, &err); 
      if (err == OS_NO_ERR) 
         throttle = (INT8U*) msg;

      /* Retardation : Factor of Terrain and Wind Resistance */
      if (velocity > 0)
         wind_factor = velocity * velocity / 10000 + 1;
      else 
         wind_factor = (-1) * velocity * velocity / 10000 + 1;

      if (position < 4000) 
         retardation = wind_factor; // even ground
      else if (position < 8000)
          retardation = wind_factor + 15; // traveling uphill
        else if (position < 12000)
            retardation = wind_factor + 25; // traveling steep uphill
          else if (position < 16000)
              retardation = wind_factor; // even ground
            else if (position < 20000)
                retardation = wind_factor - 10; //traveling downhill
              else
                  retardation = wind_factor - 5 ; // traveling steep downhill

      acceleration = *throttle / 2 - retardation;     
      position = adjust_position(position, velocity, acceleration, 300); 
      velocity = adjust_velocity(velocity, acceleration, brake_pedal, 300); 
      printf("Position: %dm\n", position / 10);
      printf("Velocity: %4.1fm/s\n", velocity /10.0);
      printf("Throttle: %dV\n", *throttle / 10);
      show_velocity_on_sevenseg((INT8S) (velocity / 10));
      //OSSemPost(aSemaphore); // Releasing the key

    }
} 

/*
 * The task 'ControlTask' is the main task of the application. It reacts
 * on sensors and generates responses.
 */

void ControlTask(void* pdata)
{
  INT8U err;
  INT8U throttle = 40; /* Value between 0 and 80, which is interpreted as between 0.0V and 8.0V */
  void* msg;
  INT16S* current_velocity;

  printf("Control Task created!\n");

  while(1)
    {
      OSSemPend(aSemaphore2, 0, &err); // Trying to access the key   
      msg = OSMboxPend(Mbox_Velocity, 0, &err);
      current_velocity = (INT16S*) msg;
      printf("Control Task!\n");
      err = OSMboxPost(Mbox_Throttle, (void *) &throttle);
      //OSSemPost(aSemaphore2); // Releasing the key
      //OSTimeDlyHMSM(0,0,0, CONTROL_PERIOD);
    }
}

/* 
 * The task 'StartTask' creates all other tasks kernel objects and
 * deletes itself afterwards.
 */ 

void StartTask(void* pdata)
{
  INT8U err;
  void* context;

  static alt_alarm alarm;     /* Is needed for timer ISR function */

  /* Base resolution for SW timer : HW_TIMER_PERIOD ms */
  delay = alt_ticks_per_second() * HW_TIMER_PERIOD / 1000; 
  printf("delay in ticks %d\n", delay);

  /* 
   * Create Hardware Timer with a period of 'delay' 
   */
  if (alt_alarm_start (&alarm,
      delay,
      alarm_handler,
      context) < 0)
      {
          printf("No system clock available!n");
      }

  /* 
   * Create and start Software Timer 
   */

  SWTimer = OSTmrCreate(0,
  CONTROL_PERIOD/(4*OS_TMR_CFG_TICKS_PER_SEC),
  OS_TMR_OPT_PERIODIC,
  release,
  NULL,
  NULL,
  &err);
     if (err == OS_ERR_NONE) {
  /* Timer was created but NOT started */
  printf("SWTimer was created but NOT started \n");
  }

  status = OSTmrStart(SWTimer,
    &err);
  if (err == OS_ERR_NONE) {
  /* Timer was started */
    printf("SWTimer was started!\n");
  }
  /*
   * Creation of Kernel Objects
   */

  // Mailboxes
  Mbox_Throttle = OSMboxCreate((void*) 0); /* Empty Mailbox - Throttle */
  Mbox_Velocity = OSMboxCreate((void*) 0); /* Empty Mailbox - Velocity */

  /*
   * Create statistics task
   */

  OSStatInit();

  /* 
   * Creating Tasks in the system 
   */


  err = OSTaskCreateExt(
       ControlTask, // Pointer to task code
       NULL,        // Pointer to argument that is
                    // passed to task
       &ControlTask_Stack[TASK_STACKSIZE-1], // Pointer to top
                             // of task stack
       CONTROLTASK_PRIO,
       CONTROLTASK_PRIO,
       (void *)&ControlTask_Stack[0],
       TASK_STACKSIZE,
       (void *) 0,
       OS_TASK_OPT_STK_CHK);

  err = OSTaskCreateExt(
       VehicleTask, // Pointer to task code
       NULL,        // Pointer to argument that is
                    // passed to task
       &VehicleTask_Stack[TASK_STACKSIZE-1], // Pointer to top
                             // of task stack
       VEHICLETASK_PRIO,
       VEHICLETASK_PRIO,
       (void *)&VehicleTask_Stack[0],
       TASK_STACKSIZE,
       (void *) 0,
       OS_TASK_OPT_STK_CHK);

  printf("All Tasks and Kernel Objects generated!\n");

  /* Task deletes itself */

  OSTaskDel(OS_PRIO_SELF);
}

/*
 *
 * The function 'main' creates only a single task 'StartTask' and starts
 * the OS. All other tasks are started from the task 'StartTask'.
 *
 */

int main(void) {

  printf("Cruise Control 2014\n");
  aSemaphore = OSSemCreate(1); // binary semaphore (1 key)  
  aSemaphore2 = OSSemCreate(0); // binary semaphore (1 key)    
  OSTaskCreateExt(
     StartTask, // Pointer to task code
         NULL,      // Pointer to argument that is
                    // passed to task
         (void *)&StartTask_Stack[TASK_STACKSIZE-1], // Pointer to top
                             // of task stack 
         STARTTASK_PRIO,
         STARTTASK_PRIO,
         (void *)&StartTask_Stack[0],
         TASK_STACKSIZE,
         (void *) 0,  
         OS_TASK_OPT_STK_CHK | OS_TASK_OPT_STK_CLR);

  OSStart();

  return 0;
}

输出:

Cruise Control 2014
delay in ticks 100
SWTimer was created but NOT started 
SWTimer was started!
All Tasks and Kernel Objects generated!
Vehicle task created!
SWTimer1 was created but NOT started 
SWTimer1 was started!
Control Task created!
Position: 0m
Velocity:  0.4m/s
Throttle: 3V
release key!
released key!
Control Task!
Position: 0m
Velocity:  0.9m/s
Throttle: 4V
release key!
released key!
Control Task!
Position: 0m
Velocity:  1.4m/s

Answer 1

我的印象是您有两个要定期运行的任务。你想用软件定时器和信号量来完成这个。如果这是正确的，那么您可以按如下方式完成此操作。

每个任务都会使用它自己的信号量和计时器。信号量可用作事件已发生的信号。在这种情况下，使用信号量来指示计时器已过期并且该是任务运行的时间了。设置软件计时器定期到期并调用回调函数。回调函数应该发布到信号量。该任务应在其 while 循环中的信号量上挂起。这样，每次计时器到期时，任务都会在循环中运行一次迭代。

这是一些伪代码:

void TimerCallback(params)
{
    // Post to the semaphore to signal that it's time to run the task.
}

void TaskFunction(void)
{
    // Create a semaphore to represent the "it's time to run" event.
    // Initialize the semaphore count to zero because it's not time
    // to run yet.

    // Create a periodic software timer which calls TimerCallback()
    // when it expires.

    while(1)
    {
        // Wait until it's time to run by pending on the semaphore.

        // Do task specific stuff.
    }
}

这种软件定时器和信号量实现的周期性特性比使用 OSTimeDlyHMSM() 更精确。原因是软件定时器周期独立于任务的执行时间运行。但是 OSTimeDlyHMSM() 的周期是在任务执行时间之外的。如果任务被其他任务或中断抢占，则任务的执行时间可能会从一个迭代到下一个迭代发生变化。因此，使用 OSTimeDlyHMSM() 并不是获取周期性事件的非常精确的方法。