The given code creates and initializes a small static JSON...

The given code creates and initializes a small static JSON document using the ArduinoJson library, which is often used in embedded systems for handling JSON data. Here's what the code does step by step:

1. StaticJsonDocument<128> doc;

   • This creates a static JSON document with a capacity of 128 bytes. The StaticJsonDocument is specifically allocated on the stack (not the heap), making it suitable for memory-limited devices.

2. doc["Node-id"] = Node-ID-Number;

   • This adds a key-value pair to the JSON object. The key is "Node-id", and the value assigned is Node-ID-Number. The Node-ID-Number is likely a variable (which should be defined elsewhere in your code) containing a specific node identifier.

3. doc["level"] = 134.2;

   • This adds another key-value pair to the JSON object. The key is "level", and the value is the floating-point number 134.2. A comment suggests that this value should be replaced by a real Time-of-Flight (ToF) sensor reading in actual use.

4. doc["battery"] = 3.72;

   • This adds a third key-value pair to the JSON object. The key is "battery", and the value is 3.72, representing a battery voltage level or state of charge.

Final JSON Object

After executing these lines of code, the doc will contain the following structured JSON object:

{
  "Node-id": Node-ID-Number, // The value of Node-ID-Number variable
  "level": 134.2,
  "battery": 3.72
}

Summary

This code initializes a JSON document with information about a node, including its ID (Node-id), a "level" reading (e.g., sensor data), and battery voltage. It is commonly used in IoT applications to prepare JSON data for transmission or logging.