The SparkFun OpenLog is an open-source serial data logger based on the ATmega328 running at 16 MHz. It logs incoming serial data directly to a microSD card, supporting cards from 64 MB to 64 GB in FAT16 or FAT32 format. Simply connect a serial line from your project to the OpenLog, and all transmitted data is stored to the card as text files.

The OpenLog draws approximately 5 mA on average, rising to around 6 mA when actively writing a 512-byte buffer. It supports configurable baud rates and is well suited for long-term data acquisition, debugging, and any application where a record of serial output is needed.

Key Features

• Simple Serial Interface – Connect via serial TX/RX to log data automatically
• microSD Storage – Supports 64 MB to 64 GB cards (FAT16/FAT32)
• ATmega328 Processor – 16 MHz with open-source firmware
• Low Power – Approximately 5–6 mA during operation
• Configurable Baud Rate – Adjustable via configuration file on the SD card
• Automatic File Creation – Creates new log files on each power cycle

Specifications

• Microcontroller – ATmega328 at 16 MHz
• Storage – microSD (64 MB – 64 GB, FAT16/FAT32)
• Current Draw – ~5 mA average, ~6 mA peak (during write)
• Default Baud Rate – 9600 bps (configurable)
• Logic Level – 3.3 V

Ideal For

• Serial data logging and scientific data acquisition
• Debugging and black-box recording of project output
• Remote or unattended sensor data collection
• Flight data recorders and environmental monitoring

Package Contents

• 1× SparkFun OpenLog

Resources

• Hookup Guide (SparkFun)
• GitHub Repository