+1 to avoid using the String class on Arduino. Use C string arrays instead, they're well-behaved.
PaulS:
if i do this :
chaine=String(adresse)+" "+String(Valeur)+" a="+String(a)+" b="+String(b)+" c="+String(c);
Serial.println(chaine);
then bugWhat kind of bug? Converting each value to a separate String is completely unnecessary.
In this snippet you have 5 calls to the String constructor (requiring 5 calls to the matching destructor)
Even worse, the compiler is going to typecast the rest into Strings too. Then for every + the String chaine gets copied over as the larger version (chaine + nextString) as a new String and that keeps going on for all 9 parts.
When are the old copies of chaine destructed? Right after concatenation?
Even worst case, I don't see enough just there to fill 1k of ram.