mbed-os/mbed_lib.json

{
    "name": "core",
    "config": {
        "stdio-convert-newlines": {
            "help": "Enable conversion to standard newlines on stdin/stdout",
            "value": false
        },

        "stdio-baud-rate": {
            "help": "Baud rate for stdio",
            "value": 9600
        }
    }
}