Description

This example show how to deserialize a MessagePack input with ArduinoJson. The process is very similar to the JSON deserialization.

An online demo of this example is available on wandbox.org.

Source code

#include <ArduinoJson.h>

void setup() {
  // Initialize serial port
  Serial.begin(9600);
  while (!Serial) continue;

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

  // StaticJsonObject allocates memory on the stack, it can be
  // replaced by DynamicJsonObject which allocates in the heap.
  //
  // DynamicJsonObject doc(200);

  // MessagePack 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.
  uint8_t input[] = {131, 166, 115, 101, 110, 115, 111, 114, 163, 103, 112, 115,
                     164, 116, 105, 109, 101, 206, 80,  147, 50,  248, 164, 100,
                     97,  116, 97,  146, 203, 64,  72,  96,  199, 58,  188, 148,
                     112, 203, 64,  2,   106, 146, 230, 33,  49,  169};
  // This MessagePack document contains:
  // {
  //   "sensor": "gps",
  //   "time": 1351824120,
  //   "data": [48.75608, 2.302038]
  // }

  // doc 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.
  DeserializationError error = deserializeMsgPack(doc, input);

  // Test if parsing succeeds.
  if (error) {
    Serial.print("deserializeMsgPack() failed: ");
    Serial.println(error.c_str());
    return;
  }

  // Get the root object in the document
  JsonObject root = doc.as<JsonObject>();

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

  // Print values.
  Serial.println(sensor);
  Serial.println(time);
  Serial.println(latitude, 6);
  Serial.println(longitude, 6);
}

void loop() {
  // not used in this example
}

Functions used in this example