qmk_firmware/tmk_core/tool/mbed/mbed-sdk/libraries/tests/mbed/blinky/main.cpp

#include "mbed.h"

DigitalOut myled(LED1);

int main() {
    while(1) {
        myled = 1;
        wait(0.2);
        myled = 0;
        wait(0.2);
    }
}