Tom's Life Bits

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This breakout has 9 GPIO: #0, #2, #4, #5, #12, #13, #14, #15, #16 all GPIO are 3.3V logic level in and out, and are not 5V compatible.  Read the full spec sheet to learn more about the GPIO pin limits, but be aware the maximum current drawn per pin is 12mA.
These pins are general purpose and can be used for any sort of input or output. Most also have the ability to turn on an internal pullup. Many have special functionality:\\
  * GPIO #0, which does not have an internal pullup, and is also connected to both a mini tactile switch and red LED. This pin is used by the ESP8266 to determine when to boot into the bootloader. If the pin is held low during power-up it will start bootloading! That said, you can always use it as an output, and blink the red LED.
  * *GPIO #2, is also used to detect boot-mode. It also is connected to the blue LED that is near the WiFi antenna. It has a pullup resistor connected to it, and you can use it as any output (like #0) and blink the blue LED.
  * *GPIO #15, is also used to detect boot-mode. It has a pulldown resistor connected to it, make sure this pin isn't pulled high on startup. You can always just use it as an output
  * *GPIO #16 can be used to wake up out of deep-sleep mode, you'll need to connect it to the RESET pin

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