ElectronParade

Hey everyone! Welcome back. So far, we’ve done a lot of cool things with the ESP32, but today we’re unlocking one of its true superpowers: the internet.

We live in a world overflowing with data—weather forecasts, stock prices, space station locations, you name it. What if your microcontroller could reach out and grab that information in real-time? Today, we’re going to connect our ESP32 to Wi-Fi, make a request to a live Web API, and parse the response so our board can actually understand it.

What We’re Building

Here is what we are going to cover in this lesson:

• Connecting your ESP32 to your local Wi-Fi network.
• Making an HTTP GET request to a public API.
• Extracting the exact data we need using the amazing ArduinoJson library.
• Displaying the live data on the Serial Monitor.

The Magic of JSON and ArduinoJson

Most web APIs speak a language called JSON (JavaScript Object Notation). It’s incredibly readable for humans, but microcontrollers need a little help parsing it efficiently. That’s where the ArduinoJson library comes in.

First, make sure you’ve installed ArduinoJson from the Library Manager in the Arduino IDE.

Here is a quick snippet showing how we fetch and parse data using a simple public time API:

#include <WiFi.h>
#include <HTTPClient.h>
#include <ArduinoJson.h>

const char* ssid = "YOUR_WIFI_SSID";
const char* password = "YOUR_WIFI_PASSWORD";
const char* apiUrl = "http://worldtimeapi.org/api/timezone/America/Toronto";

void setup() {
  Serial.begin(115200);
  WiFi.begin(ssid, password);

  Serial.print("Connecting to Wi-Fi");
  while (WiFi.status() != WL_CONNECTED) {
    delay(500);
    Serial.print(".");
  }
  Serial.println("\nConnected!");

  fetchData();
}

void loop() {
  // We'll just fetch once in setup for this example
}

void fetchData() {
  if (WiFi.status() == WL_CONNECTED) {
    HTTPClient http;
    http.begin(apiUrl);
    
    int httpResponseCode = http.GET();
    
    if (httpResponseCode > 0) {
      String payload = http.getString();
      Serial.println("Data received. Parsing JSON...");
      
      // Allocate the JSON document
      // Use arduinojson.org/v6/assistant to compute the capacity.
      StaticJsonDocument<1024> doc;
      
      // Deserialize the JSON document
      DeserializationError error = deserializeJson(doc, payload);
      
      if (error) {
        Serial.print(F("deserializeJson() failed: "));
        Serial.println(error.f_str());
        return;
      }
      
      // Fetch values
      const char* datetime = doc["datetime"]; 
      
      Serial.print("Current Date and Time: ");
      Serial.println(datetime);
      
    } else {
      Serial.print("Error code: ");
      Serial.println(httpResponseCode);
    }
    
    http.end();
  }
}

Next Steps

Now that your ESP32 can talk to the internet, the possibilities are practically endless. You could trigger a relay when the weather forecast predicts freezing temperatures, or change an RGB LED strip’s color based on the current price of a stock.

Grab your board, plug in your Wi-Fi credentials, and give it a try!

Hardware You’ll Need

To follow along with this lesson, you’ll need the following components:

• ESP32 Development Board
• Micro-USB Cable