Bronson_alex:
Using MAX232 to convert TTL-RS232 is more reliable and more consistent data than using SoftwareSerial (with inverted logic parameter), but then you cannot use Serial for debugging/monitoring.
Thanks, Bronson.
But if I choose to use the T-15A standard USB cable connecting with the Arduino Mega with a USB host, do I still need the converter ? And should I still use the SoftwareSerial to send commands and receive responses if the two devices are connected by USB?