mbed-os/features/frameworks/mbed-trace/example/mbed-os-5/mbed_app.json

{
    "macros": [
        "MEM_ALLOC=malloc",
        "MEM_FREE=free"
    ],
    "target_overrides": {
        "*": {
            "platform.stdio-baud-rate": 115200,
            "platform.stdio-convert-newlines": true,
            "platform.stdio-buffered-serial": true,
            "target.features_add": ["COMMON_PAL"],
            "mbed-trace.enable": 1
        }
    }
}