Specification of Pebble Data Format

Contents

1. Introduction

1.1 Definition

1.2 Example

2. Pebble JSON Object

2.1 Sensor Data Object

2.2 Digital Signature Object

2.3 Protobuf encode

3 pebble-simulator

1. Introduction

JavaScript Object Notation (JSON) is utilized to represent the sensor data collected by a Pebble tracker as well as the corresponding ECDSA digital signature. The data type includes Number, String and Array.

1.1 Definition

The data types used in the Pebble data format are defined as follows:

Data Type	Data Size	Data Range
Array	16-bit	-32768 ~ +32768
Number	64-bit	-1.79E+308 ~ +1.79E+308
String	null-terminated string

1.2 Example

An example of the Pebble data format is shown below:

  "message": {
    "snr": 19,
    "vbat": 4167,
    "latitude": 20000,
    "longitude": 20000,
    "gasResistance": 7745665,
    "temperature": 24.389999389648438,
    "pressure": 1003,
    "humidity": 67.24214935302734,
    "light": 0,
    "temperature2": 29.3176326751709,
    "gyroscope": [
      -2,
      3,
      1
    ],
    "accelerometer": [
      -35,
      110,
      8226
    ],
    "timestamp": "1621943329",
    "random": "E1915DBE2ACCC9F3",
    "eccPubkey": "E1B955AEDF34D18921E3DC2133F2B785BA4C40DBC1502A8BF6ECE674B80E25D8822C4686723BBC3CB4A58D881DE053A1444EE1873E5916907D2F8819ECC7A1B6"
  },
  "signature": {
    "r": "597E7BF0F5C85D7A84C3C409CA358DE3C27A072587C884AE0452BD93D8F72F39",
    "s": "ACF44E758925A2454DB1880B31A3B1B11EEAE9BCEE67C423DADF8510B1A244CC"
  }

2. Pebble JSON Object

Pebble JSON Object consists of sensor data object,digital signature data object and configure object.

2.1 Sensor Data Object

The sensor data object includes the following sensor data collected by a Pebble tracker.

Sensor Data	Data Type	Description
snr	Number	Signal-to-noise ratio of NB-IoT/LET-M
vbat	Number	Votage of battery
latitude	Number	gps latitude
longitude	Number	gps longitude
gasResistance	Number	Air quality
temperature	Number	Environmental temperature
pressure	Number	Air pressure
humidity	Number	Environmental humidity
light	Number	Ambient light
gyroscope	Array	Angular velocity around the X-axis, Y-axis and Z-axis
accelerometer	Array	Acceleration along the X-axis, Y-axis and Z-axis
timestamp	String	Timestamp of sensor data sampling
random	String	Random number (16 numbers)
longitude	Number	Degrees and Decimal Minutes(DDD° MM.MMM').(eg: 11448.65815,to convert from Decimal Minutes(D° M.M') to Decimal Degrees (D.D°),114°48.65815' = 114°+ （48.65815'/60）= 114.810969°)
latitude	Number	Degrees and Decimal Minutes(DDD° MM.MMM').(eg: 3050.69225,to convert from Decimal Minutes (D° M.M') to Decimal Degrees (D.D°),30°50.69225' = 30°+ （50.69225'/60）= 30.844870°)

2.2 Digital Signature Object

The Pebble tracker utilizes ECDSA over the elliptic curve sepc256r1 to sign the collected sensor data (i.e., the "message&quot sub-object in the Pebble data format) and the digital signature data object contains the following signature data.

Digital Signature	Data Type	Description
r	Number	r value of an ECDSA signature
s	Number	s value of an ECDSA signature

2.3 Protobuf encode

Proto definition file

3. pebble-simulator

A simulator for producing pebble data, write it to a local file and publish to AWS MQTT, interact with a local or remote iotex block chain node to get a MQTT endpoint and generate RSA key pair which used to decrypt the endpoint .