These:
byte tableau[2] = {0} ;
tableau[0] = analogRead(A0) ;
tableau[1] = analogRead(A1) ;
don't go together. The analogRead function returns an int, not a byte. You are potentially losing data right there.
These:
byte tableau[2] = {0} ;
tableau[0] = analogRead(A0) ;
tableau[1] = analogRead(A1) ;
don't go together. The analogRead function returns an int, not a byte. You are potentially losing data right there.