Technical Specification

Pebble is a battery-powered, cellular-based, multi-sensor development board designed by IoTeX and Nordic Semiconductor, combining tamper-proof hardware and tamper-proof software to generate verifiable data.

Pebble is equipped with high-quality GPS, climate, motion, and light sensors. Data can be easily streamed in real-time to an MQTT endpoint for use in Cloud or blockchain-based applications.

Pebble utilizes a secure element (nRF9160) to cryptographically sign all data, providing unparalleled verifiability and traceability for asset tracking, supply chain, and other applications.

Processor

Pebble is powered by a 64 MHz Arm® Cortex®-M33, 1 MB Flash and 256 KB RAM, with automated power and clock management, Arm TrustZone, and Arm CryptoCell 310

Integrated Sensors

Pebble combines an environmental sensor (temperature, relative humidity, barometric pressure, altitude, and volatile organic compounds - VOCs), a motion sensor (3-axis gyroscope, 3-axis accelerometer), and an ambient light sensor. It's also equipped with cellular network connectivity and integrated GPS supporting precise, long range tracking of asset data using established cellular infrastructure.

Sensor

Details

Environmental Sensor BME680

Relative humidity

Barometric pressure

Ambient temperature

Air quality (VOC)

Motion Sensor ICM-42605

3-axis gyroscope

3-axis accelerometer

External GPS TD1030

Position accuracy: 3m

Speed accuracy: 0.1 m/s

Data frequency: 1 hz to 10 Hz

Ambient Light Sensor AMS TSL2572

45,000,000:1 Dynamic Range

Operation to 60,000 lux in Sunlight

Very High Sensitivity

Package UV Rejection Filter

Buzzer Mallory Sonalert AST7525MATRQ

Frequency: 2700 Hz

Sound Pressure Level (dB/min): 85 at 10cm

Network Connectivity

Pebble includes a Multimode LTE-M/NB-IoT modem for cellular communication. To have your Pebble connected to the Internet you will need an IoT-enabled** SIM card that supports either NB-IoT or LTE standards.

Data format

JavaScript Object Notation (JSON) is utilized to represent the sensor data collected by a Pebble as well as the corresponding ECDSA digital signature. Pebble utilizes ECDSA over the elliptic curve sepc256r1 to sign the collected sensor data (i.e., the message field in the Pebble data format)

Supported data types include Number, String and Array 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

An example of a JSON object containing a data point collected by the Pebble is shown below, it consists of a sensor data object named "message", and a digital signature data object named "signature":

{
message: {
SNR: 2,
VBAT: 4.0750732421875,
latitude: 3050.69225,
longitude: 11448.65815,
gas_resistance: 1166811,
temperature: 36.23188400268555,
pressure: 1003.82000732421885,
humidity: 55.755001068115234,
light: 1639.67767,
gyroscope: [-12, 11, 14],
accelerometer: [-711, -231, 8260],
timestamp: 3443547577,
random: "3767398368",
rsa_n: "0xa709e2f84ac0e21eb0caa018cf7f697...8f628698f0c7b420c4b7",
rsa_e: "0x010001"
},
signature: {
r: "D7797968EAA3FFE5F8057C9D97F707A4A96CBFC250115FE6293EBA5E90327174",
s: "643A8CB823110376A5D30201463CF69CDF8CBF1C050EB85B023CABFB589C3222"
}
}

The message object includes the following sensor data:

Sensor Data

Data Type

Description

SNR

Number

Signal-to-noise ratio of NB-IoT/LET-M

VBAT

Number

Voltage of battery

latitude

Number

gps latitude

longitude

Number

gps longitude

gas_resistance

Number

Air quality (indoor)

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

Number

A random number generated by the onboard random number generator

rsa_n

Number

Modulus of the RSA keys (only provided in specific applications where on-chain data encryption is involved)

rsa_e

Number

Public exponent of the RSA keys (only provided in specific applications where on-chain data encryption is involved)

The 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

Onboard RGB Led

Pebble includes an RGB led to show the status of the Pebble, the table below shows all the possible led states and the respective meaning:

LED Color (Blink Rate)

GPS Signal

Charging

NB-IoT/LTE Connection

Flashing the Firmware

Blue (fast)

Blue (slow)

Red (steady) + Purple (fast)

Red (steady) + Purple (slow)

Cyan (fast)

Cyan (slow)

Red (steady) + White (fast)

Red (steady) + White (slow)

Red (fast)

Note that the led will blink at least twice in 1 second when in fast mode, and once in 5 seconds when in slow mode.

2D Drawing