Creating JSON with ArduinoJson Library

Creating JSON with ArduinoJson Library

JSON Example Data

  • Consider we want to send the following JSON data to a website
[
 {"key":"temperature", "value":79.000000},
 {"key":"humidity", "value":22.000000},
 {"key":"weather", "value": "sunny"}
]

Creating JSON with a Library: ArduinoJson

  • ArduinoJson is a popular library for generating JSON code and can be installed from Workbench

  • Use the sample code below

Configuration of ArduinoJson

  • Import library and set up Arduino compatibility
#define ARDUINOJSON_ENABLE_ARDUINO_STRING 1
#include <ArduinoJson.h>

Photon 2 code

void loop() {
  StaticJsonDocument<1024> doc; // object to store JSON response
  String output; 			   // will store JSON string which is used for Particle.publish()

  /* Here is where JSON creation code goes */
    //create first JSON object
  JsonObject obj0 = doc.createNestedObject();
  obj0["key"] = "temperature";
  obj0["value"] = 79.000000;

  //create second JSON object
  JsonObject obj1 = doc.createNestedObject();
  obj1["key"] = "humidity";
  obj1["value"] = 22.000000;

  //create third JSON object
  JsonObject obj2 = doc.createNestedObject();
  obj2["key"] = "weather";
  obj2["value"] = "sunny";

  serializeJson(doc, output); //create JSON string
  
  //make sure to change the event name below to match the webhook you created  
  Particle.publish("inital_state_json", output);
  delay(60000);	//use delay or millis to avoid publishing too frequently
}

Reference

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