LP2536.A: PWM Output, 25w36

As a fun continued learning about analog Input/Output with Arduino, based on last Learning Package LP2519: Analog Input, 25w19, we now gradually start to build some basic concept of "Analog Output", using PWM as to simulate such signals. This learning package is short, we focus on basic experience of analog output, and combine previous experience of digital I/O, analog input to build a few fun projects, we expect a very basic conceptual understanding of PWM and analog output for this Learning Package, the related knowledge will be deepen in future learning courses.