GPIO Pin BTN LED naming conventions specific to ESP8266

The esp8266 is a chip, and various different modules are available that may on may not have the LED.

There is a module called nodemcu that maps the PIN numbers on the nodemcu board to gpio numbers, so that might be useful for you. The flash button is always wired to the same gpio in, so you can use that for testing. This is what is checked on power up to put the chip into flashing mode, so when the board is running you can check the button state.

Here is an example with a button and a led, and also reading a temperature sensor, so just remove that part of the code:

http://forum.espruino.com/conversations/­282721/#comment12822865