The SparkFun OpenLog is an open source data logger that works over a simple serial connection and supports microSD cards up to 64GB. The OpenLog can store or log huge amounts of serial data and act as a black box of sorts to store all the serial data that your project generates, for scientific or debugging purposes.
The SparkFun OpenLog runs off of an onboard ATmega328, running at 16MHz thanks to the onboard crystal.The ATmega328 has the Optiboot bootloader loaded on it, which allows the OpenLog to be compatible with the "Arduino Uno" board setting in the Arduino IDE.The OpenLog draws 6mA when recording a 512 byte buffer, but as that process takes a fraction of a second, the average current draw is closer to 5mA. Keep in mind though that if you are recording a constant data stream at 115200bps, you will approach that 6mA limit.
All data logged by the OpenLog is stored on the microSD card that involve the features of 64MB to 64GB capacity and FAT16 or FAT32 file type.
The primary interface with the OpenLog is the FTDI header on the board edge. This header is designed to plug directly into an Arduino Pro or Pro Mini, which allows the microcontroller to send the data over a serial connection to the OpenLog.