I'm using TimerOne.h for collecting sensor (two photocells) data with a frequency of 100 ms and saving the data to a SD card. The file only seems to save data when the computer is connected to the board (com port open). I want the program to collect data without the serial monitor running. There's nothing in my code that would prevent the file info to be saved. Could an open com port be a requirement for the TimerOne library? Using Uno R3. Data collection occurs at 100 ms using an interrupt routine.