A small arduino program to log data from the UART port to an SD card very quickly. Works at 115200 baud.
Files on the SD card are named LOG00000.TXT, LOG00001.TXT, etc Each file is always 512,000 bytes, and the parts that have not been written to yet are all 0's
You can increase the arduino's internal serial buffer at
C:\Program Files (x86)\Arduino\hardware\arduino\cores\arduino\HardwareSerial.cpp
by changing the line #define SERIAL_BUFFER_SIZE 64. (Works great when set to 500, but is close to the memory limit)
Adopted from the RawWrite.ino example found here
Also used code from OpenLog