RX and TX are the serial control and bootloading pins, and are how you will spend most of your time communicating

with the ESP module

The TX pin is the output from the module and is 3.3V logic.

The RX pin is the input into the module and is 5V compliant (there is a level shifter on this pin)

These are connected through to the CP2104 USB-to-Serial converter so they should

not be connected to or used

unless you're super sure you want to because you will also be getting the USB traffic on these!

I2C & SPI pins

You can use the ESP8266 to control I2C and SPI devices, sensors, outputs, etc. While this is done by 'bitbanging', it

works quite well and the ESP8266 is fast enough to match 'Arduino level' speeds.

In theory you can use

any pins for I2C and SPI but to make it easier for people using existing Arduino code, libraries,

sketches we set up the following:

I2C SDA = GPIO #4 (default)

I2C SCL = GPIO #5 (default)

© Adafruit Industries

https://learn.adafruit.com/adafruit-feather-huzzah-esp8266

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