ClearGrow Probe

nRF52840-based wireless sensor probe for indoor growing environments. Communicates with the ClearGrow Controller via Thread mesh networking.

Features

• Thread MTD/SED: Minimal Thread Device with Sleepy End Device support for battery optimization
• Multi-Sensor Support: Climate, leaf temperature, substrate, CO2, and PAR sensors
• Code-Based Pairing: Easy enrollment with controller via PSKd code
• Low Power: Deep sleep modes for extended battery life
• CoAP Communication: Efficient sensor data transmission via CoAP over Thread

Hardware

• MCU: nRF52840 (ARM Cortex-M4F, 64MHz)
• Radio: IEEE 802.15.4 for Thread networking
• Power: 3.0V LiPo battery with USB charging
• Sensors (modular):
  • SHT4x: Temperature/humidity (climate)
  • MLX90614: IR leaf temperature
  • ADS1115: ADC for soil moisture/EC/pH
  • SCD4x: CO2 sensor
  • VEML7700: PAR/light sensor

Project Structure

probe/
├── src/
│   ├── main.c              # Application entry point
│   ├── thread_node.c       # Thread networking and CoAP client
│   ├── sensor_manager.c    # Sensor polling and data aggregation
│   ├── power_manager.c     # Sleep modes and battery monitoring
│   └── pairing_code.c      # PSKd generation and storage
├── include/
│   └── probe_config.h      # Configuration and type definitions
├── boards/                 # Board-specific devicetree overlays
├── dts/                    # Devicetree source files
├── prj.conf                # Zephyr project configuration
├── Kconfig                 # Custom Kconfig options
└── CMakeLists.txt          # Build configuration

Building

Prerequisites

• Zephyr SDK 0.16.0 or later
• West build tool
• nRF Connect SDK (recommended)

Setup

# Initialize west workspace (if not already done)
west init -m https://github.com/nrfconnect/sdk-nrf
west update

# Build for nRF52840 DK
west build -b nrf52840dk_nrf52840

# Flash
west flash

Configuration

Key configuration options in prj.conf:

• CONFIG_OPENTHREAD_MTD=y - Minimal Thread Device mode
• CONFIG_OPENTHREAD_JOINER=y - Enable joiner for commissioning
• CONFIG_PM=y - Power management enabled

Protocol

The probe sends sensor data to the controller using TLV (Type-Length-Value) format over CoAP:

Packet Format:

Header (12 bytes):
  [0-7]   Probe ID (EUI-64)
  [8]     Protocol Version
  [9]     Battery Percent
  [10-11] Sequence Number

Measurements (TLV, repeating):
  [Type]      Sensor type (1 byte)
  [ValueInfo] Type<<4 | Length (1 byte)
  [Value]     Sensor reading (1-4 bytes)

Measurement Types:

Type	Sensor
0x01	Temperature
0x02	Humidity
0x03	CO2
0x04	PPFD
0x05	VPD
0x06	Leaf Temperature
0x07	Soil Moisture
0x08	Soil Temperature
0x09	EC
0x0A	pH
0x0B	DLI
0x0C	Dew Point

License

Proprietary - ClearGrow Inc.