what evil genius at Keil decided that using 'm:\file.txt' with fopen/fwrite will open the file, and act as if data is written to it, but not actually write anything? ... it only took me 12 hours to figure out that 'M:\file.txt' will behave the same way but with the added benefit that .. IT WORKS! Ah you guys are killing me! :-)
Yes, flash FS had a nasty way of dealing with file names. It seems that anything that fits into 8.3 format is expected in uppercase. Long file names are expected in lower case...