Price: $43.39


Description: The SparkFun OpenLog is an open source data logger. Simple to use, simple to change. We wanted to create a serial logger that just worked. Power up this device and it will start logging any received serial data at 9600bps. Sending Ctrl+z three times will drop out of logging and in to command mode. �new� will create a new file. �md� makes a directory. �?� brings up the list of commands. OpenLog doesn�t do a lot, but it does log serial streams extremely well. Example:

 >new testfile.txt  
 >append testfile.txt  
 <(send large amounts of text followed by three ctrl+z characters)

That�s really it! OpenLog firmware is open source and is based on Bill Greiman�s sdfatlib. OpenLog currently supports FAT16 and FAT32 microSD cards (we�ve tested up to 64GB!).

All the design files (schematic, PCB layout, firmware) are open source released under the CC-SA v3 license and are available through GitHub.

Note: New firmware is available which allows the OpenLog to be used in Arduino 1.0 and also allows for higher baud rates. Check the links below for more information.


  • Log to low-cost microSD FAT16/32 cards up to 16GB
  • Simple command interface
  • Edit config.txt file from a computer to change baud rate and other system settings
  • Three modes:
    • NewLog creates a new log every power up and immediately starts logging
    • SeqLog appends a file called �SeqLog.txt� at every power up and immediately starts logging
    • Command mode starts OpenLog at a command prompt at power up
  • Configurable baud rates (2400 to 115200bps)
  • Configure unit through config file or the menu system
  • Power, ground, and RX-I are the minimum connections
  • Reprogrammable ATmega328 using the Arduino IDE
  • Two LEDs indicate writing status
  • Input voltage from 3.3V to 12V
  • 2mA idle, 6mA at maximum recording rate

Dimensions: 0.16 x 0.6 x 0.75" (4 x 15 x 19mm)


The OpenLog project is housed on GitHub! Please see the wiki for the most up-to-date firmware, feature requests, files, and datasheet specs.