Use mbed on Nucleo-64 bits STM32f303RE ARM board with the four red LEDs as lighting devices to design 'Automatic Lighting Control'. There are five required levels of lighting, 1, 2, 3, 4 and off. The lighting level is controlled by the lightness/darkness detected by the LDR sensor, for example when it is very light, all the LEDs will be off, and when it is very dark all the four LEDs will be on. All the 5 levels of lighting will be corresponded to the evenly distributed ReadIn value from the LDR. Use PWM to control brightness of the 4 LEDs.