使用ArduinoJson库解析json数据，基于Version 6

• 第一步：申请内存，这个一定要根据自己的需求去申请内存大小。

  // Allocate the JSON document
  //
  // Inside the brackets, 200 is the capacity of the memory pool in bytes.
  // Don't forget to change this value to match your JSON document.
  // Use arduinojson.org/v6/assistant to compute the capacity.
  StaticJsonDocument<200> doc;
  

• 包装数据

    // JSON input string.
  //
  // It's better to use a char[] as shown here.
  // If you use a const char* or a String, ArduinoJson will
  // have to make a copy of the input in the JsonBuffer.
  char json[] =
  "{\"sensor\":\"gps\",\"time\":1351824120,\"data\":[48.756080,2.302038]}";
  
  // Root of the object tree.
  //
  // It's a reference to the JsonObject, the actual bytes are inside the
  // JsonBuffer with all the other nodes of the object tree.
  // Memory is freed when jsonBuffer goes out of scope.
  JsonObject& root = jsonBuffer.parseObject(json);
  

• 验证

  // Deserialize the JSON document
  DeserializationError error = deserializeJson(doc, json);
  
  // Test if parsing succeeds.
  if (error) {
    Serial.print(F("deserializeJson() failed: "));
    Serial.println(error.f_str());
    return;
  }
  

• Json数据的解析

  // Fetch values.
  //
  // Most of the time, you can rely on the implicit casts.
  // In other case, you can do doc["time"].as<long>();
  const char* sensor = doc["sensor"];
  long time = doc["time"];
  double latitude = doc["data"][0];
  double longitude = doc["data"][1];
  
  // Print values.
  Serial.println(sensor);
  Serial.println(time);
  Serial.println(latitude, 6);
   Serial.println(longitude, 6);
  }
  

• 包装Json数据