Un début de piste ?
Dans le Scope de l'arduino j'ai ces messages :
/var/folders/r2/zblqdvd97zsbs3l9spzb1t5r0000gn/T/arduino_modified_sketch_634080/GSMSim_SMS.ino: In function 'void setup()':
/var/folders/r2/zblqdvd97zsbs3l9spzb1t5r0000gn/T/arduino_modified_sketch_634080/GSMSim_SMS.ino:33:18: warning: deprecated conversion from string constant to 'char*' [-Wwrite-strings]
char* number = "06256743**";
^
/var/folders/r2/zblqdvd97zsbs3l9spzb1t5r0000gn/T/arduino_modified_sketch_634080/GSMSim_SMS.ino:34:19: warning: deprecated conversion from string constant to 'char*' [-Wwrite-strings]
char* message = "Hi my friend. How are you?"; // message lenght must be <= 160. Only english characters.
^