Schneggi sensor 🐌

A low-power ZigBee sensor integrated with HomeAssistant for monitoring temperature, humidity, and CO2.

• High accuracy temperature and humidity measurements (Sensirion SHTC3)
• High accuracy CO2 measurement (Sensirion SCD40) - optional board
• Low power consumption and long battery life
  • Hardware: nRF52840 chip, low-current linear regulator, battery monitor with on/off capability
  • Software: Zigbee sleepy end device
  • Measured: 3uA average over 1 minute (without CO2). 3mA average over 1 minute (with CO2 low-power mode)
• Can be powered with 3V to 6V (JST connector), e.g. 350mAh li-poly.
• Small footprint (3,5cm x 3cm )
• Tested with Home Assistant and SkyConnect

PCB

The PCB was designed with KiCad 7 and manufactured/assembled with JLCPCB. All relevant files can be found in the repo

HomeAssistant

Case

Build

This project uses a west workspace (manifest in west.yml) and a local Makefile wrapper.

1) One-time workspace setup

From the project directory:

west init -l .
cd ..
west update

This initializes a west workspace in the parent directory and fetches all required modules (including modules/sensirion_drivers for SCD4X).

2) Build

cd <project-dir>
make build

Default output:

• build_west/merged.hex
• build_west/schneggi-sensor/zephyr/zephyr.elf

3) Test (host unit tests)

make test

4) Flash

make flash

Useful overrides

make build BUILD_DIR=build_debug
make build CONF_FILE=prj_production.conf
make flash SNR=<your_jlink_serial>

Keep dependencies in sync

After updating west.yml:

make west-update

Resources

• The PCB design was inspired by Getting Started With nRF52 MCU in a PCB
• The repos zigbee-plant-sensor and b-parasite are a great start
• The Zyphr driver for SCD40
• The nRF Sniffer with https://www.wireshark.org is a helpful tool to debug Zigbee communication
• The ZigBee specification 22 1.0 and ZigBee Cluster Library R8