🛠 Deux tâches FreeRTOS sur les deux cœurs

Objectives

Leverage the true strength of the ESP32: its dual Xtensa cores. You will create two FreeRTOS tasks, each pinned to a specific core, communicating via a queue. Typical use case: keep core 0 for the Wi-Fi/Bluetooth stack and core 1 for your application logic, just as the Arduino loop already does.

Hardware

• 1 ESP32 DevKit v1 board
• A PC with a serial port
• No soldering required

Full code

#include <WiFi.h>

QueueHandle_t file;
struct Mesure { float t; int rssi; };

void tacheReseau(void*) {       // epinglee sur coeur 0, pres de la pile Wi-Fi
  for (;;) {
    Mesure m;
    m.t = millis / 1000.0f;
    m.rssi = WiFi.RSSI;
    xQueueSend(file, &m, portMAX_DELAY);
    vTaskDelay(pdMS_TO_TICKS(1000));
  }
}

void tacheConsole(void*) {      // epinglee sur coeur 1
  Mesure m;
  for (;;) {
    if (xQueueReceive(file, &m, portMAX_DELAY)) {
      Serial.printf("[coeur %d] t=%.0f s RSSI=%d\n",
                    xPortGetCoreID, m.t, m.rssi);
    }
  }
}

void setup {
  Serial.begin(115200);
  file = xQueueCreate(16, sizeof(Mesure));
  WiFi.mode(WIFI_STA);
  xTaskCreatePinnedToCore(tacheReseau,  "reseau",  4096, NULL, 5, NULL, 0);
  xTaskCreatePinnedToCore(tacheConsole, "console", 4096, NULL, 4, NULL, 1);
}

void loop { vTaskDelay(pdMS_TO_TICKS(1000)); }

Expected verification

The console displays a line every second: "[core 1] t=… s RSSI=…". The measurement is produced on core 0, consumed, and displayed on core 1. If you remove the pinning, the displayed core number changes depending on FreeRTOS scheduling.

Common errors

• Stack too small (4096 bytes here): a slightly heavy printf can crash the task (Guru Meditation); monitor uxTaskGetStackHighWaterMark.
• Two tasks writing to Serial simultaneously: interleaved output; centralize displays or protect with a mutex.
• Slow Wi-Fi calls made from loop: the radio stack runs on core 0, hence the benefit of task separation.
• delay works within a task (it yields control), but vTaskDelay(pdMS_TO_TICKS(…)) remains the explicit FreeRTOS syntax.