# Adafruit TCA8418 Keypad Matrix and GPIO Expander Breakout
## Overview
It's a GPIO expander, it's a keypad matrix driver... it's the **Adafruit TCA8418 Keypad Matrix and GPIO Expander Breakout** - a cute and powerful I2C GPIO expander _and _keypad matrix driver! This chip is quite fancy, with the ability to act as your I2C multi-tool for handling keypads, buttons or LEDs.
This chip has 18 total 'I/O' pins, 10 columns and 8 rows. You can of course arrange them as a matrix of buttons for a total of 80 switches. Or you can use any subset as individual GPIO input or outputs. The nicest part of the keypad driver is that it has a 10-element event queue, so even if you don't get to the interrupt immediately, keypress and release events will be held for you. Since it's I2C, it's very easy to use with any microcontroller or computer.
GPIO expanders work like this: you have a board with some number of GPIO but not enough for your project - maybe you need more buttons or LEDs. [You _could_ upgrade to a board with massive number of GPIO like the Grand Central](https://www.adafruit.com/?q=grand+central&sort=BestMatch), or you could pop on one of these boards.
Connect it over I2C and then you can send/receive I2C commands to control the GPIO pins to write and read them. It's going to be slower than direct GPIO access, but maybe that doesn't matter if it takes a millisecond instead of a microsecond. You only need the two I2C pins, and you can even share the I2C port with other sensors and devices. Heck, you can even add more expanders for massive I/O control!
For GPIO expansion, any of the 18 pins can be used as input or output. For inputs, you can also set an optional pull-up and an interrupt output on the INT pin for rising or falling signals. There's also a debouncer that can add a little low-pass filtering for noisy tactile switches. For outputs, you can set them high or low, great for basic LED driving.
[We've written both Arduino](https://github.com/adafruit/Adafruit_TCA8418) and [CircuitPython/Python libraries](https://github.com/adafruit/Adafruit_CircuitPython_TCA8418) for the TCA8418, so you can get started whether you have an Arduino-compatible UNO or a Raspberry Pi 4 - or anything in between. [There's also a Linux Kernel driver module](https://github.com/torvalds/linux/blob/master/drivers/input/keyboard/tca8418_keypad.c) if you want to have this natively supported by a single-board-computer.
To get you going fast, we spun up a custom-made PCB in the [**STEMMA QT** form factor](https://www.adafruit.com/?q=stemma%20qt%20sensor "STEMMA QT form factor"), making it easy to interface with. There's a built in 3.3V regulator and level shifting on the I2C lines so you can use this with 3V or 5V microcontrollers.
The [STEMMA QT connectors](https://learn.adafruit.com/introducing-adafruit-stemma-qt/what-is-stemma-qt) on either side are compatible with the [SparkFun Qwiic](https://www.sparkfun.com/qwiic) I2C connectors. This allows you to make solderless connections between your development board and the TCA8418 or to chain it with a wide range of other sensors and accessories using a [**compatible cable**](https://www.adafruit.com/?q=stemma%20qt%20cable). [**QT Cable is not included** , but we have a variety in the shop](https://www.adafruit.com/?q=stemma+qt+cable&sort=BestMatch).
# Adafruit TCA8418 Keypad Matrix and GPIO Expander Breakout
## Pinouts
The default I2C address is **0x34.**
## Power Pins
- **VIN** - this is the power pin. Since the keypad chip uses 3 VDC, we have included a voltage regulator on board that will take 3-5VDC and safely convert it down. To power the board, give it the same power as the logic level of your microcontroller - e.g. for a 5V microcontroller like Arduino, use 5V.
- **3Vo** - this is the 3.3V output from the voltage regulator, you can grab up to 100mA from this if you like.
- **GND** - common ground for power and logic.
## I2C Logic Pins
- **SCL ** - I2C clock pin, connect to your microcontroller I2C clock line. This pin is level shifted so you can use 3-5V logic, and there's a **10K pullup** on this pin.
- **SDA ** -I2C data pin, connect to your microcontroller I2C data line. This pin is level shifted so you can use 3-5V logic, and there's a **10K pullup** on this pin.
- **[STEMMA QT](https://learn.adafruit.com/introducing-adafruit-stemma-qt) - **These connectors allow you to connectors to dev boards with **STEMMA QT** connectors or to other things with [various associated accessories](https://www.adafruit.com/?q=JST%20SH%204).
## GPIO Pins
- **C0** - **C9** - GPIO or column pins in a keypad matrix. Column number corresponds with pin number
- **R0** - **R7** - GPIO or row pins in a keypad matrix. Row number corresponds with pin number
## Other Pins
- **INT ** - Open-drain active-low interrupt output
- **RST** - Active-low reset input
## Power LED
- **Power LED - ** This LED is a green LED located on the front of the board. It is labeled **on**.
# Adafruit TCA8418 Keypad Matrix and GPIO Expander Breakout
## Python & CircuitPython
It's easy to use the **TCA8418** with Python or CircuitPython, and the [Adafruit\_CircuitPython\_TCA8418](https://github.com/adafruit/Adafruit_CircuitPython_TCA8418) module. This module allows you to easily write Python code that reads the TCA8418's GPIO pins as a GPIO expander or keypad matrix. You can use this breakout with any CircuitPython microcontroller board or with a computer that has GPIO and Python [thanks to Adafruit\_Blinka, our CircuitPython-for-Python compatibility library](https://learn.adafruit.com/circuitpython-on-raspberrypi-linux).
## CircuitPython Microcontroller Wiring
First, wire up a TCA8418 and keypad to your board exactly as shown below. Here's an example of wiring a Feather M4 to the breakout with I2C using one of the handy [**STEMMA QT**](https://learn.adafruit.com/introducing-adafruit-stemma-qt) connectors:
**TCA8418**
- **Board 3V** to **breakout VIN (red wire)**
- **Board GND** to **breakout** **GND (black wire)**
- **Board SCL** to **breakout**** SCL (yellow wire)**
- **Board SDA** to **breakout**** SDA (blue wire)**
**Keypad**
- **Pin 1** to **breakout C3**
- **Pin 2** to **breakout C2**
- **Pin 3** to **breakout C1**
- **Pin 4** to **breakout C0**
- **Pin 5** to **breakout R2**
- **Pin 6** to **breakout R1**
- **Pin 7** to **breakout R0**
You can also use standard **0.100" pitch** headers to wire it up on a breadboard:
**TCA8418**
- **Board 3V** to **breakout VIN (red wire)**
- **Board GND** to **breakout** **GND (black wire)**
- **Board SCL** to **breakout**** SCL (yellow wire)**
- **Board SDA** to **breakout**** SDA (blue wire)**
**Keypad**
- **Pin 1** to **breakout C3**
- **Pin 2** to **breakout C2**
- **Pin 3** to **breakout C1**
- **Pin 4** to **breakout C0**
- **Pin 5** to **breakout R2**
- **Pin 6** to **breakout R1**
- **Pin 7** to **breakout R0**
## Python Computer Wiring
Since there's _dozens_ of Linux computers/boards you can use, below shows wiring for Raspberry Pi. For other platforms, [please visit the guide for CircuitPython on Linux to see whether your platform is supported](https://learn.adafruit.com/circuitpython-on-raspberrypi-linux).
Here's the Raspberry Pi wired to the breakout using I2C and a [**STEMMA QT**](https://learn.adafruit.com/introducing-adafruit-stemma-qt) connector:
**TCA8418**
- **Pi 3V** to **breakout VIN (red wire)**
- **Pi GND** to **breakout** **GND (black wire)**
- **Pi SCL** to **breakout**** SCL (yellow wire)**
- **Pi SDA** to **breakout**** SDA (blue wire)**
**Keypad**
- **Pin 1** to **breakout C3**
- **Pin 2** to **breakout C2**
- **Pin 3** to **breakout C1**
- **Pin 4** to **breakout C0**
- **Pin 5** to **breakout R2**
- **Pin 6** to **breakout R1**
- **Pin 7** to **breakout R0**
Finally here is an example of how to wire up a Raspberry Pi to the sensor using a solderless breadboard:
**TCA8418**
- **Pi 3V** to **breakout VIN (red wire)**
- **Pi GND** to **breakout** **GND (black wire)**
- **Pi SCL** to **breakout**** SCL (yellow wire)**
- **Pi SDA** to **breakout**** SDA (blue wire)**
**Keypad**
- **Pin 1** to **breakout C3**
- **Pin 2** to **breakout C2**
- **Pin 3** to **breakout C1**
- **Pin 4** to **breakout C0**
- **Pin 5** to **breakout R2**
- **Pin 6** to **breakout R1**
- **Pin 7** to **breakout R0**
## Python Installation of TCA8418 Library
You'll need to install the **Adafruit\_Blinka** library that provides the CircuitPython support in Python. This may also require enabling I2C on your platform and verifying you are running Python 3. [Since each platform is a little different, and Linux changes often, please visit the CircuitPython on Linux guide to get your computer ready](https://learn.adafruit.com/circuitpython-on-raspberrypi-linux)!
Once that's done, from your command line run the following command:
- `pip3 install adafruit-circuitpython-tca8418`
If your default Python is version 3, you may need to run `pip` instead. Make sure you aren't trying to use CircuitPython on Python 2.x, it isn't supported!
## CircuitPython Usage
To use with CircuitPython, you need to first install the TCA8418 library, and its dependencies, into the **lib** folder on your **CIRCUITPY** drive. Then you need to update **code.py** with the example script.
Thankfully, we can do this in one go. In the example below, click the **Download Project Bundle** button below to download the necessary libraries and the **code.py** file in a zip file. Extract the contents of the zip file, and copy the **entire **** lib ** ** folder ** and the ** code.py ** file to your ** CIRCUITPY** drive.
Your **CIRCUITPY/lib** folder should contain the following folders and file:
- **adafruit\_bus\_device/**
- **adafruit\_register/**
- **adafruit\_tca8418.mpy**
## Python Usage
Once you have the library `pip3` installed on your computer, copy or download the following example to your computer, and run the following, replacing **code.py** with whatever you named the file:
`python3 code.py`
## Keypad Example Code
https://github.com/adafruit/Adafruit_CircuitPython_TCA8418/blob/main/examples/tca8418_3x4_noOLED.py
**If running CircuitPython:** Once everything is saved to the **CIRCUITPY** drive, [connect to the serial console](https://learn.adafruit.com/welcome-to-circuitpython/kattni-connecting-to-the-serial-console) to see the data printed out!
**If running Python: ** The console output will appear wherever you are running Python.
In the example, the TCA8418 is instantiated on I2C. Then, the keypad matrix is setup. The key names are setup in a matrix as well.
In the loop, every time you press or release a key the key event is printed to the REPL, followed by the row, column and key name that was used in the event.
## GPIO Expander Example Code
**TCA8418**
- **Board 3V** to **breakout VIN (red wire)**
- **Board GND** to **breakout **** GND (black wire)**
- **Board SCL** to **breakout**** SCL (yellow wire)**
- **Board SDA** to **breakout**** SDA (blue wire)**
**LED**
- **Anode** to **breakout R0 (green wire)**
- **Cathode** to **board GND (black wire)**
**Button**
- **Input** to **breakout R1 (pink wire)**
- **GND** to **board GND (black wire)**
https://github.com/adafruit/Adafruit_CircuitPython_TCA8418/blob/main/examples/tca8418_gpiobutton.py
In the GPIO expander example, the TCA8418 is instantiated on I2C. Then, `R0` is setup as and output for the LED and `R1` is setup as an input for the button.
In the loop, every time the button is pressed, the LED turns off. When the button is released, the LED turns on.
# Adafruit TCA8418 Keypad Matrix and GPIO Expander Breakout
## Python Docs
# Adafruit TCA8418 Keypad Matrix and GPIO Expander Breakout
## Arduino
Using the TCA8418 with Arduino involves wiring up the breakout to your Arduino-compatible microcontroller, installing the [Adafruit\_TCA8418](https://github.com/adafruit/Adafruit_TCA8418) library and running the provided example code.
## Wiring
Wire as shown for a **5V** board like an Uno. If you are using a ** 3V** board, like an Adafruit Feather, wire the board's 3V pin to the TCA8418 VIN.
Here is an Adafruit Metro wired up to the TCA8418 using the STEMMA QT connector:
**STEMMA**
- **Board 5V** to **breakout VIN (red wire)**
- **Board GND** to **breakout** **GND (black wire)**
- **Board SCL** to **breakout**** SCL (yellow wire)**
- **Board SDA** to **breakout**** SDA (blue wire)**
**Keypad**
- **Pin 1** to **breakout C3**
- **Pin 2** to **breakout C2**
- **Pin 3** to **breakout C1**
- **Pin 4** to **breakout C0**
- **Pin 5** to **breakout R2**
- **Pin 6** to **breakout R1**
- **Pin 7** to **breakout R0**
Here is an Adafruit Metro wired up using a solderless breadboard:
**STEMMA**
- **Board 5V** to **breakout VIN (red wire)**
- **Board GND** to **breakout** **GND (black wire)**
- **Board SCL** to **breakout**** SCL (yellow wire)**
- **Board SDA** to **breakout**** SDA (blue wire)**
**Keypad**
- **Pin 1** to **breakout C3**
- **Pin 2** to **breakout C2**
- **Pin 3** to **breakout C1**
- **Pin 4** to **breakout C0**
- **Pin 5** to **breakout R2**
- **Pin 6** to **breakout R1**
- **Pin 7** to **breakout R0**
## Library Installation
You can install the **Adafruit TCA8418 ** library for Arduino using the Library Manager in the Arduino IDE.
Click the **Manage Libraries ...** menu item, search for **Adafruit TCA8418** , and select the **Adafruit TCA8418** library:
If asked about dependencies, click "Install all".
If the "Dependencies" window does not come up, then you already have the dependencies installed.
Warning:
## Keypad Example Code
https://github.com/adafruit/Adafruit_TCA8418/blob/main/examples/tca8418_3x4_no_OLED/tca8418_3x4_no_OLED.ino
Upload the sketch to your board and open up the Serial Monitor ( **Tools -\> Serial Monitor** ) at 115200 baud. You'll see the key event, row number, column number and key name appear in the serial monitor as you press the keys.
## GPIO Example Code
**TCA8418**
- **Board 3V** to **breakout VIN (red wire)**
- **Board GND** to **breakout **** GND (black wire)**
- **Board SCL** to **breakout**** SCL (yellow wire)**
- **Board SDA** to **breakout**** SDA (blue wire)**
**Button**
- **Input** to **breakout R0 (green wire)**
- **GND** to **board GND**
https://github.com/adafruit/Adafruit_TCA8418/blob/main/examples/tca8418_gpio/tca8418_gpio.ino
Upload the sketch to your board and open up the Serial Monitor ( **Tools -\> Serial Monitor** ) at 115200 baud. All 18 of the TCA8418's inputs are read and their status, `1` for `HIGH` and `0` for `LOW`, are printed to the Serial Monitor every second.
# Adafruit TCA8418 Keypad Matrix and GPIO Expander Breakout
## Arduino Docs
# Adafruit TCA8418 Keypad Matrix and GPIO Expander Breakout
## Downloads
## Files
- [TCA8418 Datasheet](https://cdn-learn.adafruit.com/assets/assets/000/115/118/original/tca8418.pdf?1663246975)
- [EagleCAD PCB files on GitHub](https://github.com/adafruit/Adafruit-TCA8418-PCB)
- [Fritzing object in the Adafruit Fritzing Library](https://github.com/adafruit/Fritzing-Library/blob/master/parts/Adafruit%20TCA8418%20Keypad%20Matrix%20and%20GPIO%20Expander%20Breakout%20STEMMA.fzpz)
- [3D Models on GitHub](https://github.com/adafruit/Adafruit_CAD_Parts/tree/main/4918%20TCA8418%20Stemma)
## Schematic and Fab Print
## 3D Model
## Primary Products
### Adafruit TCA8418 Keypad Matrix and GPIO Expander Breakout
[Adafruit TCA8418 Keypad Matrix and GPIO Expander Breakout](https://www.adafruit.com/product/4918)
It's a GPIO expander, it's a keypad matrix driver... its the **Adafruit TCA8418 Keypad Matrix and GPIO Expander Breakout** - a cute and powerful I2C GPIO expander _and_ keypad matrix driver! This chip is quite fancy, with the ability to act as your I2C...
Out of Stock
[Buy Now](https://www.adafruit.com/product/4918)
[Related Guides to the Product](https://learn.adafruit.com/products/4918/guides)
## Featured Products
### Membrane 3x4 Matrix Keypad + extras
[Membrane 3x4 Matrix Keypad + extras](https://www.adafruit.com/product/419)
Punch in your secret key into this numeric matrix keypad. This keypad has 12 buttons, arranged in a telephone-line 3x4 grid. It's made of a thin, flexible membrane material with an adhesive backing (just remove the paper) so you can attach it to nearly anything. The keys are connected into...
In Stock
[Buy Now](https://www.adafruit.com/product/419)
[Related Guides to the Product](https://learn.adafruit.com/products/419/guides)
### 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.
In Stock
[Buy Now](https://www.adafruit.com/product/4399)
[Related Guides to the Product](https://learn.adafruit.com/products/4399/guides)
### STEMMA QT / Qwiic JST SH 4-pin Cable with Premium Female Sockets
[STEMMA QT / Qwiic JST SH 4-pin Cable with Premium Female Sockets](https://www.adafruit.com/product/4397)
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 female 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 and...
In Stock
[Buy Now](https://www.adafruit.com/product/4397)
[Related Guides to the Product](https://learn.adafruit.com/products/4397/guides)
### STEMMA QT / Qwiic JST SH 4-pin to Premium Male Headers Cable
[STEMMA QT / Qwiic JST SH 4-pin to Premium Male Headers Cable](https://www.adafruit.com/product/4209)
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...
In Stock
[Buy Now](https://www.adafruit.com/product/4209)
[Related Guides to the Product](https://learn.adafruit.com/products/4209/guides)
### 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.
Out of Stock
[Buy Now](https://www.adafruit.com/product/4210)
[Related Guides to the Product](https://learn.adafruit.com/products/4210/guides)
## Related Guides
- [Split Ortho Keyboard with TCA8418 Matrix Expanders](https://learn.adafruit.com/split-ortho-keyboard.md)
- [Adafruit ATtiny Breakouts with seesaw](https://learn.adafruit.com/adafruit-attiny817-seesaw.md)
- [Bluetooth Restroom Key Proximity Tracker](https://learn.adafruit.com/bluetooth-restroom-key-proximity-tracker.md)
- [Adafruit QT Py and NeoPixel LEDs](https://learn.adafruit.com/qt-py-and-neopixel-leds.md)
- [Adafruit AW9523 GPIO Expander and LED Driver](https://learn.adafruit.com/adafruit-aw9523-gpio-expander-and-led-driver.md)
- [Adafruit MCP3421 18-Bit ADC](https://learn.adafruit.com/adafruit-mcp3421-18-bit-adc.md)
- [Doomscroll and Chill - A Wireless BLE Scroll Wheel Remote](https://learn.adafruit.com/doomscroll-and-chill-wireless-ble-scroll-wheel-rotary-encoder-remote.md)
- [Adafruit PowerBoost 500 Shield](https://learn.adafruit.com/adafruit-powerboost-500-shield-rechargeable-battery-pack.md)
- [Adafruit AS7331 UV / UVA / UVB / UVC Sensor](https://learn.adafruit.com/adafruit-as7331-uv-uva-uvb-uvc-sensor.md)
- [Adafruit Wii Nunchuck Breakout Adapter](https://learn.adafruit.com/adafruit-wii-nunchuck-breakout-adapter.md)
- [Living Starry Night Painting](https://learn.adafruit.com/animated-starry-night-circuit-playground-express.md)
- [Adafruit EYESPI BFF](https://learn.adafruit.com/adafruit-eyespi-bff.md)
- [Solderless Robot Toy Xylophone](https://learn.adafruit.com/solderless-robot-toy-xylophone.md)
- [GitHub Actions Status Tower Light](https://learn.adafruit.com/github-actions-status-tower-light.md)
- [Adafruit PyBadge and PyBadge LC](https://learn.adafruit.com/adafruit-pybadge.md)