Example Description

This example describes how to use UART TX to simulate clock source

Required Components:
    Oscilloscope

UART0 pin mappings used in this test demo:
            PA23(TX)
            PA18(RX)

UART0 or UART1 can be used for us.
Connect the TX pin of UART0 with the oscilloscope, and 
we can watch the clock source waveform we want to generate.

This example shows: 
1. Clock signal output from UART1_TX to oscilloscope
