I am using F() in string constant to save RAM memory, but for unknown reason if I add one more F() on a string I have unexpected behavior in my sketch (increased read values on analog pin) ??? very strange. If I remove the extra F(), everything OK again.....
My sketch is about 23kB and I still have 700 B of RAM due to F() (against 550B before without F()) - using Arduino Uno + Ethernet shield, Rev 1.00.
I tried to find some documentation about F() but could find nothing at all on the Arduino site.
It's also easy to use EEPROM library as it's described : http://arduino.cc/en/Reference/EEPROM
May be it can help you and it will use less memory.
Storing and Readding datas is really simple, you juste have to care about the index in the eeprom to be ok.
Hope it can help you.
My sketch is about 23kB and I still have 700 B of RAM due to F() (against 550B before without F())
How are you measuring the amount of free memory? Specifically, where are you measuring it? Each function call takes memory, to push the values being passed to the function.