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JSON Parsing (Reading Web Data) | NexaLearn IoT Lab | NexaLearn

Internet of Things (IoT)30 دقيقة

JSON Parsing (Reading Web Data)

How the ESP32 understands complex data coming from the web.

Lesson Content

When you request weather data from a server, it returns it as a JSON text: {"temp":25, "city":"Riyadh"} To programmatically extract the number 25, we use the ArduinoJson library which deserializes the text and converts it to useful variables safely within limited memory.

Components Needed

ESP32مكتبة ArduinoJson

Code Example

#include <ArduinoJson.h>
void setup() {
  Serial.begin(9600);
  String input = "{\"temp\":25, \"city\":\"Riyadh\"}";
  StaticJsonDocument<200> doc;
  deserializeJson(doc, input);
  int t = doc["temp"]; // 25
  String c = doc["city"]; // Riyadh
  Serial.println(t);
}
void loop() {}

Common Mistakes

Allocating a buffer (memory size) for the JSON document smaller than the actual size of the received data, causing silent parsing failure.

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