The Arduino DUE has given many a difficult time in getting the SD working. I needed to get everything working prior to porting some pet projects to the faster platform. Code here is working on CTE TFT LCD/SD shield for DUE (V1.04), and WOMARTS 320x240 display
Surprise! The SD on the "CTE TFT LCD/SD shield for DUE," worked first up after soldering "J8", and using the SPARKFUN SD.lib ( SD.begin(53,75,74,76) )
I designed the base platform code so the graphical display could be instantly scaled to whatever size and placement required without any extra coding, and simply requires declaring the sizes as required. Now, this makes for slower code, but is handy in a lot of circumstances.
Also slowing the display is the fudge I use to avoid constant grid re-draws, that is, store grid positions and avoid plotting over them.
Cursor method also slows active graphing, but very useful in analyzing a static display.
Keyboard placement of cursor is next. Detail and code at excelworks.info