How to use ESP32 Dual Core with Arduino IDE (Multi thread)

 How to use ESP32 Dual Core with Arduino IDE

源自於https://randomnerdtutorials.com/esp32-dual-core-arduino-ide/

https://youyouyou.pixnet.net/blog/post/120275992-%E7%AC%AC%E4%BA%8C%E5%8D%81%E7%AF%87-esp32-%E7%89%B9%E6%AE%8A%E6%87%89%E7%94%A8%EF%BC%9A%E5%A4%9A%E5%9F%B7%E8%A1%8C%E7%B7%92

擁有兩個核心，不過平常都只用到一個核心，這樣是不是很浪費，我們如何善用增加效能呢？或者如何使用平行處理呢？本章分為三個部份解說：
一、    多核心概念
二、    顯示執行核心
三、    雙核心執行

一、多核心概念
我們常聽到說我的手機有4核心，電腦有8核心，所謂的多核心（Multi-core）簡單的說就是CPU能同時處理較多的任務且不會互相干擾，另外一種虛擬的多核心稱為多執行緒（Thread）則是CPU的分時多工，非本篇的討論範圍，由於ESP32有著240/160MHz的雙核心CPU，因此本篇將要說明是能將任務指定給核心執行的「xTaskCreatePinnedToCore」函數。

ESP32多核心的寫法，步驟是這樣的
1.    宣告任務變數：TaskHandle_t Task1;
2.    設定並執行任務：//設定任務
       xTaskCreatePinnedToCore(
         Task1code, //本任務實際對應的Function
         "Task1",      //任務名稱（自行設定）
         10000,        //所需堆疊空間（常用10000）
         NULL,         //輸入值
         0,               //優先序：0代表最優先執行，1次之，以此類推
         &Task1,     //對應的任務handle變數
         0);              //指定執行核心編號（0、1或tskNO_AFFINITY：系統指定）

The ESP32 comes with 2 Xtensa 32-bit LX6 microprocessors: core 0 and core 1. So, it is dual core. When we run code on Arduino IDE, by default, it runs on core 1. In this post we’ll show you how to run code on the ESP32 second core by creating tasks. You can run pieces of code simultaneously on both cores, and make your ESP32 multitasking.

Note: you don’t necessarily need to run dual core to achieve multitasking.

Introduction

The ESP32 comes with 2 Xtensa 32-bit LX6 microprocessors, so it’s dual core:

• Core 0
• Core 1

When we upload code to the ESP32 using the Arduino IDE, it just runs – we don’t have to worry which core executes the code.

Create Tasks

The Arduino IDE supports FreeRTOS for the ESP32, which is a Real Time Operating system. This allows us to handle several tasks in parallel that run independently.

Tasks are pieces of code that execute something. For example, it can be blinking an LED, making a network request, measuring sensor readings, publishing sensor readings, etc…

To assign specific parts of code to a specific core, you need to create tasks. When creating a task you can chose in which core it will run, as well as its priority. Priority values start at 0, in which 0 is the lowest priority. The processor will run the tasks with higher priority first.

To create tasks you need to follow the next steps:

1. Create a task handle. An example for Task1:

TaskHandle_t Task1;

2. In the setup() create a a task assigned to a specific core using the xTaskCreatePinnedToCore function. That function takes several arguments, including the priority and the core where the task should run (the last parameter).

xTaskCreatePinnedToCore(
      Task1code, /* Function to implement the task */
      "Task1", /* Name of the task */
      10000,  /* Stack size in words */
      NULL,  /* Task input parameter */
      0,  /* Priority of the task */
      &Task1,  /* Task handle. */
      0); /* Core where the task should run */

3. After creating the task, you should create a function that contains the code for the created task. In this example you need to create the Task1code() function. Here’s how the task function looks like:

Void Task1code( void * parameter) {
  for(;;) {
    Code for task 1 - infinite loop
    (...)
  }
}

The for(;;) creates an infinite loop. So, this function runs similarly to the loop() function. You can use it as a second loop in your code, for example.

If during your code execution you want to delete the created task, you can use the vTaskDelete()function, that accepts the task handle (Task1) as argument:

vTaskDelete(Task1);

Let’s see how these concepts work with a simple example.

Create Tasks in Different Cores – Example

To follow this example, you need the following parts:

• ESP32 DOIT DEVKIT V1 Board
• 2x 5mm LED
• 2x 330 Ohm resistor
• Breadboard
• Jumper wires

You can use the preceding links or go directly to MakerAdvisor.com/tools to find all the parts for your projects at the best price!

To create different tasks running on different cores we’ll create two tasks that blink LEDs with different delay times. Start by wiring two LEDs to the ESP32 as shown in the following diagram:

We’ll create two tasks running on different cores:

• Task1 runs on core 0;
• Task2 runs on core 1;

Upload the next sketch to your ESP32 to blink each LED in a different core:

/*********
  Rui Santos
  Complete project details at https://randomnerdtutorials.com  
*********/

TaskHandle_t Task1;
TaskHandle_t Task2;

// LED pins
const int led1 = 2;
const int led2 = 4;

void setup() {
  Serial.begin(115200); 
  pinMode(led1, OUTPUT);
  pinMode(led2, OUTPUT);

  //create a task that will be executed in the Task1code() function, with priority 1 and executed on core 0
  xTaskCreatePinnedToCore(
                    Task1code,   /* Task function. */
                    "Task1",     /* name of task. */
                    10000,       /* Stack size of task */
                    NULL,        /* parameter of the task */
                    1,           /* priority of the task */
                    &Task1,      /* Task handle to keep track of created task */
                    0);          /* pin task to core 0 */                  
  delay(500); 

  //create a task that will be executed in the Task2code() function, with priority 1 and executed on core 1
  xTaskCreatePinnedToCore(
                    Task2code,   /* Task function. */
                    "Task2",     /* name of task. */
                    10000,       /* Stack size of task */
                    NULL,        /* parameter of the task */
                    1,           /* priority of the task */
                    &Task2,      /* Task handle to keep track of created task */
                    1);          /* pin task to core 1 */
    delay(500); 
}

//Task1code: blinks an LED every 1000 ms
void Task1code( void * pvParameters ){
  Serial.print("Task1 running on core ");
  Serial.println(xPortGetCoreID());

  for(;;){
    digitalWrite(led1, HIGH);
    delay(1000);
    digitalWrite(led1, LOW);
    delay(1000);
  } 
}

//Task2code: blinks an LED every 700 ms
void Task2code( void * pvParameters ){
  Serial.print("Task2 running on core ");
  Serial.println(xPortGetCoreID());

  for(;;){
    digitalWrite(led2, HIGH);
    delay(700);
    digitalWrite(led2, LOW);
    delay(700);
  }
}

void loop() {
  
}

View raw code

How the Code Works

Note: in the code we create two tasks and assign one task to core 0 and another to core 1. Arduino sketches run on core 1 by default. So, you could write the code for Task2 in the loop() (there was no need to create another task). In this case we create two different tasks for learning purposes.

However, depending on your project requirements, it may be more practical to organize your code in tasks as demonstrated in this example.

The code starts by creating a task handle for Task1 and Task2 called Task1 and Task2.

TaskHandle_t Task1;
TaskHandle_t Task2;

Assign GPIO 2 and GPIO 4 to the LEDs:

const int led1 = 2; 
const int led2 = 4;

In the setup(), initialize the Serial Monitor at a baud rate of 115200:

Serial.begin(115200);

Declare the LEDs as outputs:

pinMode(led1, OUTPUT); 
pinMode(led2, OUTPUT);

Then, create Task1 using the xTaskCreatePinnedToCore() function:

xTaskCreatePinnedToCore(
             Task1code, /* Task function. */
             "Task1",   /* name of task. */
             10000,     /* Stack size of task */
             NULL,      /* parameter of the task */
             1,         /* priority of the task */
             &Task1,    /* Task handle to keep track of created task */
             0);        /* pin task to core 0 */

Task1 will be implemented with the Task1code() function. So, we need to create that function later on the code. We give the task priority 1, and pinned it to core 0.

We create Task2 using the same method:

xTaskCreatePinnedToCore(
             Task2code,  /* Task function. */
             "Task2",    /* name of task. */
             10000,      /* Stack size of task */
             NULL,       /* parameter of the task */
             1,          /* priority of the task */
             &Task2,     /* Task handle to keep track of created task */
             1);         /* pin task to core 0 */

After creating the tasks, we need to create the functions that will execute those tasks.

void Task1code( void * pvParameters ){
  Serial.print("Task1 running on core ");
  Serial.println(xPortGetCoreID());

  for(;;){
    digitalWrite(led1, HIGH);
    delay(1000);
    digitalWrite(led1, LOW);
    delay(1000);
  }
}

The function to Task1 is called Task1code() (you can call it whatever you want). For debugging purposes, we first print the core in which the task is running:

Serial.print("Task1 running on core ");
Serial.println(xPortGetCoreID());

Then, we have an infinite loop similar to the loop() on the Arduino sketch. In that loop, we blink LED1 every one second.

The same thing happens for Task2, but we blink the LED with a different delay time.

void Task2code( void * pvParameters ){
  Serial.print("Task2 running on core ");
  Serial.println(xPortGetCoreID());

  for(;;){
    digitalWrite(led2, HIGH);
    delay(700);
    digitalWrite(led2, LOW);
    delay(700);
  }
}

Finally, the loop() function is empty:

void loop() { }

Note: as mentioned previously, the Arduino loop() runs on core 1. So, instead of creating a task to run on core 1, you can simply write your code inside the loop().

Demonstration

Upload the code to your ESP32. Make sure you have the right board and COM port selected.

Open the Serial Monitor at a baud rate of 115200. You should get the following messages:

As expected Task1 is running on core 0, while Task2 is running on core 1.

In your circuit, one LED should be blinking every 1 second, and the other should be blinking every 700 milliseconds.