IoT を使ってみる（その１２：FreeRTOS排他制御編）

#if CONFIG_FREERTOS_UNICORE
#define ARDUINO_RUNNING_CORE 0
#else
#define ARDUINO_RUNNING_CORE 1
#endif

#ifndef LED_BUILTIN
#define LED_BUILTIN 13
#endif

// 変更する値
#define PRI_HIGH  2 // タスクHIGHの優先度
#define PRI_LOW  2  // タスクLOWの優先度
#define TASK_DELAY  1000 // タスクの待ち時間
#define SEM_BLOCK_TIME  portMAX_DELAY // セマフォのブロック時間 (portMAX_DELAY は待ち時間無し)

// Declare a mutex Semaphore Handle which we will use to manage the Serial Port.
// It will be used to ensure only one Task is accessing this resource at any time.
SemaphoreHandle_t xSerialSemaphore;

// define two tasks for Blink & AnalogRead
void Task_BlinkHigh( void *pvParameters );
void Task_BlinkLow( void *pvParameters );

// the setup function runs once when you press reset or power the board
void setup() {
  
  // initialize serial communication at 115200 bits per second:
  Serial.begin(115200);

  // Semaphores are useful to stop a Task proceeding, where it should be paused to wait,
  // because it is sharing a resource, such as the Serial port.
  // Semaphores should only be used whilst the scheduler is running, but we can set it up here.
  if ( xSerialSemaphore == NULL )  // Check to confirm that the Serial Semaphore has not already been created.
  {
    xSerialSemaphore = xSemaphoreCreateMutex();  // Create a mutex semaphore we will use to manage the Serial Port
  }

  // initialize digital LED_BUILTIN on pin 13 as an output.
  pinMode(LED_BUILTIN, OUTPUT);
  
  // Now set up two tasks to run independently.
  xTaskCreatePinnedToCore(
    Task_BlinkHigh
    ,  "Task_BlinkHigh"   // A name just for humans
    ,  1024  // This stack size can be checked & adjusted by reading the Stack Highwater
    ,  NULL
    ,  PRI_HIGH  // Priority, with 3 (configMAX_PRIORITIES - 1) being the highest, and 0 being the lowest.
    ,  NULL 
    ,  ARDUINO_RUNNING_CORE);

  xTaskCreatePinnedToCore(
    Task_BlinkLow
    ,  "Task_BlinkLow"   // A name just for humans
    ,  1024  // This stack size can be checked & adjusted by reading the Stack Highwater
    ,  NULL
    ,  PRI_LOW  // Priority, with 3 (configMAX_PRIORITIES - 1) being the highest, and 0 being the lowest.
    ,  NULL 
    ,  ARDUINO_RUNNING_CORE);

  // Now the task scheduler, which takes over control of scheduling individual tasks, is automatically started.
}

void loop()
{
  // Empty. Things are done in Tasks.
}

/*--------------------------------------------------*/
/*---------------------- Tasks ---------------------*/
/*--------------------------------------------------*/

void Task_BlinkHigh(void *pvParameters)  // This is a task.
{
  (void) pvParameters;
  
  for (;;) // A Task shall never return or exit.
  {
    // See if we can obtain or "Take" the Serial Semaphore.
    // If the semaphore is not available, wait blocktime ticks of the Scheduler to see if it becomes free.
    //Serial.println("Wait Take Semaphore - HIGH");
    if ( xSemaphoreTake( xSerialSemaphore, ( TickType_t ) SEM_BLOCK_TIME ) == pdTRUE )
    {
      digitalWrite(LED_BUILTIN, HIGH);   // turn the LED on (HIGH is the voltage level)
      Serial.println("HIGH");
      vTaskDelay(TASK_DELAY);  // one tick delay (15ms) in between reads for stability

      xSemaphoreGive( xSerialSemaphore ); // Now free or "Give" the Serial Port for others.
    } else {
      Serial.println("Not Take Semaphore - HIGH");
    }
  }
}

void Task_BlinkLow(void *pvParameters)  // This is a task.
{
  (void) pvParameters;

  for (;;) // A Task shall never return or exit.
  {
    // See if we can obtain or "Take" the Serial Semaphore.
    // If the semaphore is not available, wait blocktime ticks of the Scheduler to see if it becomes free.
    //Serial.println("Wait Take Semaphore - LOW");
    if ( xSemaphoreTake( xSerialSemaphore, ( TickType_t ) SEM_BLOCK_TIME ) == pdTRUE )
    {
      digitalWrite(LED_BUILTIN, LOW);    // turn the LED off by making the voltage LOW
      Serial.println("LOW");
      vTaskDelay(TASK_DELAY);  // one tick delay (15ms) in between reads for stability

      xSemaphoreGive( xSerialSemaphore ); // Now free or "Give" the Serial Port for others.
    } else {
      Serial.println("Not Take Semaphore - LOW");
    }    
  }
}

if ( xSerialSemaphore == NULL )
{
  xSerialSemaphore = xSemaphoreCreateMutex();
}

if ( xSemaphoreTake( xSerialSemaphore, ( TickType_t ) SEM_BLOCK_TIME ) == pdTRUE )
{
  // 処理
}

xSemaphoreGive( xSerialSemaphore );

#define PRI_HIGH  2 // タスクHIGHの優先度
#define PRI_LOW  3  // タスクLOWの優先度

Serial.println("Wait Take Semaphore - HIGH");

Serial.println("Wait Take Semaphore - LOW");