// https://arduinojson.org/v6/how-to/do-serial-communication-between-two-boards/

#include <ArduinoJson.h>
String cmd2;
void setup() {
   
  // The data rate must be much higher than the "link" serial port
  Serial.begin(9600);
  while (!Serial) continue;

// RECEIVING MODE:
// Check if the other Arduino is transmitting
  if (Serial.available()) 
  {
    // Allocate the JSON document
    // This one must be bigger than the sender's because it must store the strings
    StaticJsonDocument<300> doc;

    // Read the JSON document from the "link" serial port
    DeserializationError err = deserializeJson(doc, Serial);

    if (err == DeserializationError::Ok) 
    {
 
    
String cmd2 =    doc["cmd"];
//Serial.print("cmd = ");
//Serial.println(cmd);

    } 
    else 
    {
      // Print error to the "debug" serial port
      //Serial.print("deserializeJson() returned ");
      //Serial.println(err.c_str());
  
      // Flush all bytes in the "link" serial port buffer
      while (Serial.available() > 0)
        Serial.read();
    }
  }

if (cmd2 =="get_status") {
// SENDING MODE:
// Create the JSON document
//String json;    // no need for this code
StaticJsonDocument<300> doc;
JsonObject obj = doc.createNestedObject("status");
obj["Camera"]= "tCam-Mini-EFB5";
obj["Model"]=262402;
obj["Version"]="2.0";
obj["Time"]="17:33:49.0";
obj["Date"]="2/3/21";
// Send the JSON document over the "link" serial port
serializeJson(doc, Serial);

// another way for Sending the JSON document:
/*
  String json;
  // Send the JSON document over the "link" serial port
  serializeJson(doc, json);
  Serial.println(json);
*/

     }
}
 
void loop() {}