Example Description

This example describes how to use pwm

Requirement Components:
    1~4 LED

Connect LED to below PWM pins and ground, then the LED would gradually become brighter and then darker with different speed.
 - connect a LED to PA_13 and ground
 - connect a LED to PA_30 and ground
 - connect a LED to PB_4 and ground
 - connect a LED to PB_22 and ground
 