The SparkFun Qwiic OpenLog is an I²C-based data logger that stores serial data to a microSD card. Based on the popular OpenLog, this version replaces the serial interface with I²C and Qwiic connectors, allowing you to daisy-chain multiple sensors and log data without occupying your serial port.

Powered by an ATmega328 running at 16 MHz with the Optiboot bootloader, the Qwiic OpenLog is compatible with the Arduino Uno board setting in the Arduino IDE. It supports clock stretching for reliable data transfer, recording up to 20,000 bytes per second at 400 kHz I²C. Breadboard-friendly 0.1" header pins are also broken out for non-Qwiic setups.

Key Features

• I²C Data Logging – Log data from multiple I²C devices via Qwiic daisy-chain
• microSD Storage – Supports 64 MB to 32 GB cards in FAT16 and FAT32
• 20,000 Bytes/s – High-speed recording at 400 kHz with clock stretching
• ATmega328 Processor – Arduino Uno compatible (Optiboot bootloader)
• Qwiic Connectors – Polarised JST connectors for solderless I²C wiring
• Breadboard Friendly – 0.1" header pins broken out for traditional wiring

Specifications

• Microcontroller – ATmega328 @ 16 MHz
• Interface – I²C (Qwiic / 0.1" header)
• I²C Speed – Up to 400 kHz with clock stretching
• Max Logging Rate – 20,000 bytes/s
• microSD Support – 64 MB to 32 GB, FAT16/FAT32
• Idle Current – 2–6 mA
• Recording Current – 20–23 mA (varies with microSD card)
• Bootloader – Optiboot (Arduino Uno compatible)

Ideal For

• Sensor data logging and environmental monitoring
• Project debugging and black-box recording
• Scientific data collection
• Any I²C system requiring persistent storage

Resources

• Hookup Guide