also I think I configure the baud rate cause I can change the width of the wave，but my computer can't receive the signal .
I have consider the circuit connection ，so I connect the jumpers。but in datasheet PTB11 is configured as UART3_TX,
and then the signal break off。
so how can I transport the signal to TWR-SER2's ICL3225E to change TTL to RS232 .
thanks for your help .