Try this.
dataFile = SD.open("TEST.CSV", FILE_WRITE);
Use this to "truncate"...
SD.remove("TEST.CSV");
... then open for writing and it is empty.
Try this.
dataFile = SD.open("TEST.CSV", FILE_WRITE);
Use this to "truncate"...
SD.remove("TEST.CSV");
... then open for writing and it is empty.