Note:
Bluetooth compatible function is on by default and can be turned off with serial protocol. If the compatible bluetooth is off and you can't use the serial port, you can continuously turn off the power within 2-3 seconds and then turn on the power more than 5 times to turn on the compatible bluetooth again. If compatible bluetooth is off and serial port can't be used, turn off and on more than 5 times within 2-3 seconds, then compatible bluetooth can be turned on again.
bases :
RX, receive serial
TX, serial transmission
OUT, high level sense output
GND, power ground
VCC, power supply input (5V)