mrburnette:
I know the memory is very limited on the Arduino so I'm trying to figure out the best way to do the actual project, which is to play back the 4 signals over 1200 seconds, one point per signal each second.
Personally, I would just send the data off the Arduino (use a Leonardo 32U4) too a PC over the USB. Collect the data in Excel.
Excel can then parse, analyze, graph, ...
Here is how to parse using formulas... No VBA required!
http://www.hackster.io/rayburne/arduino-to-excel-using-v-usbRay
I'm not sure you understand the project. Firstly I already have an Uno so would prefer to use that unless it absolutely won't work. Secondly I'm trying to get the data from Excel onto the Arduino, not the other way around. Sorry I wasn't clear.