# Working with I2C Devices
## Overview
**Inter-Integrate Circuit** , aka **I2C** , is an extremely popular method for connecting one or more peripheral devices, like sensor breakouts, to a host controller, like an Arduino board. It only requires two pins for data and clock and can support attaching over 100 devices. It's so popular that it even gets its own special, easy to use connector via Adafruit's [STEMMA / STEMMA QT](https://learn.adafruit.com/introducing-adafruit-stemma-qt/what-is-stemma) and [Sparkfun's Qwiic](https://www.sparkfun.com/qwiic). It's pretty much plug-and-play!
However, it's not all sunshine, rainbows, and lollipops when dealing with I2C. This guide goes into some of the main hiccups that one may encounter when dealing with I2C devices.
Info:
**If you are just wanting to use I2C devices, you don't really need to read this guide.** Ideally, you can just use an available library and follow its documentation. The library writer, to the extent possible, has taken care of the low-level details. But the information here can still be helpful. It will give more context to what the device "address" is all about, etc.
If you are curious about the struggles a library developer deals with, or are wanting to write a library for an I2C device, then this guide hopefully provides some helpful background information on some of the main technical bumps.
Or just give it a read to increase your understanding of I2C, to better understand some of the lingo, etc. There's no project here. Just a grab bag of I2C related topics. Enjoy!
## I2C Bus Specification
The original specification goes back to the 1980's and was created by what was then Phillips Semiconductors, which is now known as NXP Semiconductors. The specification is available from NXP's website here:
[I2C Bus Specification and User Manual](https://www.nxp.com/docs/en/user-guide/UM10204.pdf)
- [Next Page](https://learn.adafruit.com/working-with-i2c-devices/terminology.md)
## Featured Products
### TCA9548A I2C Multiplexer
[TCA9548A I2C Multiplexer](https://www.adafruit.com/product/2717)
You just found the perfect I2C sensor, and you want to wire up two or three or more of them to your Arduino when you realize "Uh oh, this chip has a fixed I2C address, and from what I know about I2C, you cannot have two devices with the same address on the same SDA/SCL pins!" Are you...
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### Adafruit TCA4307 Hot-Swap I2C Buffer with Stuck Bus Recovery
[Adafruit TCA4307 Hot-Swap I2C Buffer with Stuck Bus Recovery](https://www.adafruit.com/product/5159)
As we've been adding [STEMMA QT connectors](https://learn.adafruit.com/introducing-adafruit-stemma-qt/what-is-stemma-qt) to our breakouts and dev boards, folks have been really enjoying the simplicity and speed of plugging in I2C sensors and devices for quick iteration and...
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[Related Guides to the Product](https://learn.adafruit.com/products/5159/guides)
### Adafruit LTC4311 I2C Extender / Active Terminator
[Adafruit LTC4311 I2C Extender / Active Terminator](https://www.adafruit.com/product/4756)
I2C stands for Inter-Integrated-Circuit communications, it's meant for short distances on a PCB or subassembly. But, hey, we're engineers, and we like to push the limits of technology, right? So why not try to have I2C run over a meter long cable, or even longer? Well, if you try to do...
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### STEMMA QT / Qwiic JST SH 4-pin Cable - 100mm Long
[STEMMA QT / Qwiic JST SH 4-pin Cable - 100mm Long](https://www.adafruit.com/product/4210)
This 4-wire cable is a little over 100mm / 4" long and fitted with JST-SH female 4-pin connectors on both ends. Compared with the chunkier JST-PH these are 1mm pitch instead of 2mm, but still have a nice latching feel, while being easy to insert and remove.
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### STEMMA QT / Qwiic JST SH 4-Pin Cable - 50mm Long
[STEMMA QT / Qwiic JST SH 4-Pin Cable - 50mm Long](https://www.adafruit.com/product/4399)
This 4-wire cable is 50mm / 1.9" long and fitted with JST SH female 4-pin connectors on both ends. Compared with the chunkier JST PH these are 1mm pitch instead of 2mm, but still have a nice latching feel, while being easy to insert and remove.
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This 4-wire cable is a little over 150mm / 6" long and fitted with JST-SH female 4-pin connectors on one end and premium Dupont male headers on the other. Compared with the chunkier JST-PH these are 1mm pitch instead of 2mm, but still have a nice latching feel, while being easy to insert...
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### JST SH 4-pin Cable with Alligator Clips - STEMMA QT / Qwiic
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This cable will make it super easy to use our plug-and-play STEMMA QT boards with boards like Circuit Playground. On one end you get a Qwiic / STEMMA QT connector (technically known as a JST SH 4-pin plug) into 4 individual wires with grippy alligator clips. We're carrying these to...
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## Related Guides
- [Adafruit LTC4311 I2C Extender / Active Terminator](https://learn.adafruit.com/adafruit-ltc4311-i2c-extender-active-terminator.md)
- [Adafruit TCA4307 Hot-Swap I2C Buffer](https://learn.adafruit.com/adafruit-tca4307.md)
- [How to Scan and Detect I2C Addresses](https://learn.adafruit.com/scanning-i2c-addresses.md)
- [Working with Multiple Same Address I2C Devices](https://learn.adafruit.com/working-with-multiple-i2c-devices.md)
- [I2C Addresses and Troublesome Chips](https://learn.adafruit.com/i2c-addresses.md)
- [Adafruit TCA9548A 1-to-8 I2C Multiplexer Breakout](https://learn.adafruit.com/adafruit-tca9548a-1-to-8-i2c-multiplexer-breakout.md)
- [MIDI Laser Harp with Time of Flight Distance Sensors](https://learn.adafruit.com/midi-laser-harp-time-of-flight-sensors.md)
- [Adafruit IO Basics: Digital Input](https://learn.adafruit.com/adafruit-io-basics-digital-input.md)
- [CurieBot: Arduino 101 Mini Robot Rover](https://learn.adafruit.com/curiebot-arduino-101-mini-robot-rover.md)
- [Adafruit AS7341 10-Channel Light / Color Sensor Breakout](https://learn.adafruit.com/adafruit-as7341-10-channel-light-color-sensor-breakout.md)
- [Character LCD with Raspberry Pi or BeagleBone Black](https://learn.adafruit.com/character-lcd-with-raspberry-pi-or-beaglebone-black.md)
- [Adafruit LSM6DS3TR-C + LIS3MDL - Precision 9 DoF IMU](https://learn.adafruit.com/adafruit-lsm6ds3tr-c-lis3mdl-precision-9-dof-imu.md)
- [Circuit Playground Musical Glove](https://learn.adafruit.com/cpx-musical-glove.md)
- [Chumby Hacker Board](https://learn.adafruit.com/chumby-hacker-board.md)
- [Adafruit LPS28 Pressure Sensor](https://learn.adafruit.com/adafruit-lps28-pressure-sensor.md)