Hi to all!, when u want to use the UARTs/USB services are two ways, the FCM services or the raw acces.
In my personal experience i found easier use the FCM services altough it uses an autobaudrate and the eccho is aviable. This two features wasnt really wanted in my development so i used fcm services and then at commands.
So, i use the fcm to initialize and handle the data from the UARTs and USB, and with the at commands i change the baudrate, bits number, flow control and disable the eccho when the port became data mode.
Use the raw acces it brings me lots of difficulties.