blue led is connected to TX(GPIO1)
if not using TX to send serial data, can be used as an output pin
RX(GPIO3) can be used as input
GPIO1 can also be used as INPUT
GPIO1 is an OUTPUT at startup
If using as INPUT, be sure to add a series 330 Ohm resistor between the driver and INPUT pin to prevent shorting.
Setting GPIO3 (RX) as OUTPUT is not recommended.