🛠 Se connecter au Wi-Fi et interroger une API HTTP

Objectives

Connect the M5StickC Plus2 to a 2.4 GHz Wi-Fi network (the ESP32-PICO-V3-02 chip does not support 5 GHz; the v2's 3D antenna offers better range than the v1) and query an HTTP API using a GET request with the HTTPClient library, then display a value extracted from the JSON.

Hardware

• 1× M5StickC Plus2 (v2)
• 2.4 GHz Wi-Fi network + access to a simple HTTP API (e.g., http://ip.jsontest.com or a local server)
• Arduino IDE / PlatformIO: M5Unified + HTTPClient (included in the esp32 package)

Complete code

// Wi-Fi 2.4 GHz + requete HTTP GET (reconnexion auto par minute)
#include <M5Unified.h>
#include <WiFi.h>
#include <HTTPClient.h>

const char* SSID = "VOTRE_WIFI_24GHZ";
const char* PASS = "motdepasse";
const char* URL  = "http://ip.jsontest.com/";   // renvoie {"ip": "..."}

void setup {
  auto cfg = M5.config;
  M5.begin(cfg);
  Serial.begin(115200);
  M5.Display.setRotation(1);
  M5.Display.setTextSize(1);
  M5.Display.setTextColor(TFT_WHITE, TFT_BLACK);
  M5.Display.printf("WiFi %s...\n", SSID);
  WiFi.mode(WIFI_STA);                  // station uniquement
  WiFi.begin(SSID, PASS);
  while (WiFi.waitForConnectResult != WL_CONNECTED) {
    M5.Display.println("echec, nouvelle tentative...");
    delay(3000);
  }
  M5.Display.printf("IP: %s\n", WiFi.localIP.toString.c_str);
}

void boucleHttp {
  HTTPClient http;
  http.begin(URL);
  int code = http.GET;
  M5.Display.setCursor(0, 40);
  if (code == HTTP_CODE_OK) {
    String corps = http.getString;
    int i = corps.indexOf("\"ip\": \"") + 7;   // extraction JSON maison
    String ip = (i > 6) ? corps.substring(i, corps.indexOf('"', i)) : "?";
    M5.Display.setTextColor(TFT_GREEN, TFT_BLACK);
    M5.Display.printf("IP publique: %s", ip.c_str);
    Serial.println(corps);
  } else {
    M5.Display.setTextColor(TFT_RED, TFT_BLACK);
    M5.Display.printf("HTTP erreur %d", code);
  }
  http.end;
}

void loop {
  M5.update;
  if (M5.BtnA.wasPressed) boucleHttp;   // A = relancer une requete
  if (WiFi.status != WL_CONNECTED) WiFi.reconnect;
  vTaskDelay(50 / portTICK_PERIOD_MS);
}

Expected verification

After connecting, the local IP is displayed; pressing A triggers a GET request and the public IP returned by the API is displayed in green. The serial monitor shows the raw JSON body.

Common errors

• Router on 5 GHz: the chip only supports 802.11 b/g/n 2.4 GHz — the network appears "not found" even though it exists.
• Forgetting WiFi.mode(WIFI_STA) before WiFi.begin: random behavior.
• Using ADC2 (pins G25/G26) for analog readings while Wi-Fi is active: on the classic ESP32, ADC2 is unavailable when Wi-Fi is running — use ADC1 (G32/G33/G36).
• Using an https:// URL with simple HTTPClient: WiFiClientSecure is required, otherwise a connection error occurs.
• SSID/password strings with accents or improperly escaped characters in the code.
• Freezing the loop during the GET request: the interface becomes unresponsive; for a product, move the request to a FreeRTOS task.