void myButtonPressedCallback(enum mtouch_button_names button)
{
    printf("The button %d is pressed.\r\n", button);
}

void myButtonReleasedCallback(enum mtouch_button_names button)
{
    printf("The button %d is released.\r\n", button);
}

main()
{
    ...

    MTOUCH_Button_SetPressedCallback(myButtonPressedCallback);
    MTOUCH_Button_SetNotPressedCallback(myButtonReleasedCallback);
    ...

    while(1)
    {
       MTOUCH_Service_Mainloop();
    }
}