Bluetooth Adapter for Nextion User guide

Can also use USBtoTTL adapter

Test: 

AT 

Set Master

AT+ROLE=M

Set Slave
AT+ROLE=S 

Set Baud

Send:AT+BAUD2
Return:OK2400 ,support:
1--------- 1200
2--------- 2400
3--------- 4800
4--------- 9600(Default) 
5--------- 19200
6--------- 38400 
7--------- 57600 
8--------- 115200 
9--------- 230400 
A--------- 460800 
B--------- 921600 
C--------- 1382400