XIAO Logger HAT - Temperature, Humidity & Light Sensor for XIAO

XIAO Logger HAT is a tiny temperature, humidity, and light add-on module for the Seeed Studio XIAO series, adding an onboard RTC, battery voltage monitoring, and I2C sensors in a footprint that matches your XIAO board exactly. It's built for long-term, low-power data logging, sipping under 1μA when idle so it can run from a small lithium battery for extended periods.

Tiny Footprint, Built for Battery Power

The HAT fits neatly on top of any Seeed Studio XIAO board, with a small lithium-ion battery sandwiched between the dev board and the HAT itself, keeping the whole stack compact enough for space-limited projects. GPIO-powered sensors allow an almost no-power sleep mode when not in use, while the always-on RTC draws less than 1μA, making the combination well suited to battery-powered loggers that need to run unattended for long stretches.

Accurate Sensing

An SHT40 sensor provides temperature readings accurate to 0.2°C and humidity to 1.8% RH, communicating over I2C alongside a BH1750 ambient light sensor, so you can log all three readings from the same bus with minimal extra wiring.

Onboard RTC for Long-Term Logging

A PCF8563 real-time clock with its own oscillator handles timekeeping and provides a programmable interrupt for deep sleep wakeups, essential for any logger that needs to record data on a schedule over months rather than hours. In testing, the PCF8563 showed roughly a 7 minute drift over a year, compared to around 10 hours of drift from an ESP32's internal RTC over the same period.

Battery Voltage Monitoring

When connected to a lithium-ion battery, battery status can be safely monitored through a pin-enabled voltage divider, letting your logging code track remaining battery life alongside sensor data.

Open Source, Community-Designed

This board was designed by Marcel at Westlake University and brought to market through Seeed's Fusion Co-Create program, which helps scale community hardware projects into production while the designer earns a commission on each unit sold. The full schematics, PCB layout, Gerber files, and firmware are open-sourced on GitHub, where Marcel maintains ongoing software updates and support.

Note that this expansion board isn't directly compatible with the XIAO nRF54L15 series, since Arduino isn't currently supported on that board. The hardware interface itself is fully compatible, so developers can manually adapt the software if needed, and official software support from Seeed Studio is in development.

XIAO Board Compatibility

Marcel has tested the XIAO ESP32-C3, ESP32-C6, and ESP32-S3 directly, though other XIAO boards should work based on their pin configuration. The XIAO SAMD21 and RP2040 don't support battery charging and shouldn't be used with battery monitoring. The RP2350, ESP32-C6, RA4M1, and MG24 support battery charging but need additional wiring. The nRF52840, ESP32-C3, and ESP32-S3 fully support battery monitoring with a simple 2-pin header connection.

Specifications

Hardware Overview

Resources

• GitHub Repository, open-source schematics, layout, Gerber files, and firmware
• SHT40 Datasheet
• BH1750 Datasheet
• PCF8563 RTC Datasheet
• Browse our full range of XIAO Development Boards

This product can be found here:

• Accessories
• Accessories
• Arduino Shields
• Development Boards
• Hats & Other Add-ons
• Power
• Seeed Studio XIAO Expansion / Breakout Boards
• Shields/Hats & Cases