Understanding Raspberry Pi HATs: Expanding Your Pi’s Capabilities
Ready to supercharge your Raspberry Pi’s abilities. Adding better AI capabilities, or purely just adding more storage? Then HATs are the perfect solution!
Raspberry Pi first introduced their official HATs (Hardware Attached on Top) to the world in July 2014, offering a range functionalities. From AI to sensors, display and storage HATs. There a HAT for almost any project out there. Today we’ll be exploring the different HATs that you can start including in your projects.
What Exactly is a HAT?
A HAT is an officially recognized add-on board that directly connects to a Raspberry Pi’s 40-pins header. While there are a variety of boards that are able to connect to a Raspberry Pi, HATs work with specific standards which helps ensure the consistency and their plug-n-play nature. The name is more than just a clever acronym, it refers to how to boards sits atop a Raspberry Pi, aligning perfectly with the mounting holes for a secure fit.
The HAT Standard:
- Includes a tiny EEPROM (Electrically Erasable Programmable Read-Only Memory) chip. This chip stores the configuration information which is used to automatically identify the board and setup the GPIO pins and drivers.
HAT vs pHAT and Bonnets
While browsing for add-ons, you might also come across pHATs (PHATs or Pi HATs) and “Bonnets.” The main distinction is their size and adherence to the full HAT standard. A pHAT is a smaller version, typically designed to match the footprint of the compact Raspberry Pi Zero. Most importantly, these boards often lack the EEPROM chip, meaning you may need to perform some manual software configuration to get them to work. The term “Bonnet” is a generic name used for some smaller add-on boards, particularly by Adafruit, that also may not follow the official HAT specification.
Exploring Popular Types of HATs
1. Sensor and Environmental HATs
These HATs are designed to help your Raspberry Pi interact with the physical world by collecting data. They are perfect for projects that involve environmental monitoring, weather stations, or data logging. A prime example is the official Sense HAT, which includes an array of sensors for temperature, pressure, and humidity, as well as a gyroscope, accelerometer, and magnetometer. It was even used by the Astro Pi project aboard the International Space Station.
2. Audio HATs
While the Raspberry Pi can output audio through its HDMI or USB ports, Audio HATs dramatically improve sound quality. These boards often include high-quality Digital-to-Analog Converters (DACs), which are essential for audiophile-grade music players and media centers. The HiFiBerry DAC+ is a popular choice for building a home audio system with your Pi, providing crystal-clear sound output.
3. Motor and Robotics HATs
If your project requires movement, a Motor and Robotics HAT is a must-have. These HATs provide the power and control necessary to drive motors, servos, and other mechanical components. They are a staple for anyone building a robot, a remote-controlled car, or any other kinetic project. The Adafruit Motor HAT is a well-known example that allows you to control multiple DC or stepper motors with ease.
4. Display HATs
Display HATs add a visual interface to your Raspberry Pi, allowing you to create custom readouts, dashboards, or even small, portable gaming systems. They come in many forms, from simple character displays to full-color touchscreens. Waveshare Display HATs offer a wide range of options, including LCD and e-paper screens, perfect for projects that require a visual component without the bulk of a full-sized monitor.
5. Power and Communication HATs
These HATs solve common power and networking challenges. For projects in remote locations without a power outlet, a PoE+ (Power over Ethernet) HAT is invaluable, allowing the Pi to receive both power and data through a single Ethernet cable. Other HATs in this category can add cellular, GPS, or other communication modules to expand the Pi’s connectivity beyond Wi-Fi and Bluetooth.
6. AI and Storage HATs
With the increasing demand for advanced computing, this new category of HATs is gaining popularity. These boards enable the Raspberry Pi to handle demanding tasks like machine learning, computer vision, and fast data access. The Raspberry Pi AI HAT+ is a great example, using a Hailo AI accelerator to perform complex AI tasks directly on the device. Additionally, M.2 HATs allow you to add high-speed NVMe solid-state drives for blazing-fast storage, making the Pi suitable for use as a file server or for other data-intensive applications.
Choosing the right HAT is as important as the project itself. Considering the following points when choosing what you need:
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Project Goal: Start with the “why.” What is the main purpose of your project? Are you trying to build a robot, a home media server, or a weather station? Your goal will immediately narrow down the category of HATs you should be looking at.
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Pi Compatibility: While many HATs work with all Raspberry Pi models that have the 40-pin GPIO header, some are designed for specific models (e.g., a PoE HAT for a Pi 4). Always double-check the product specifications to confirm compatibility with your particular Pi model.
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Software Support: A HAT is useless without the right software. Look for HATs that have well-documented drivers and libraries, preferably in a language like Python, as this will make it much easier to integrate the hardware into your code.
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Power Requirements: Most HATs draw power directly from the Raspberry Pi’s GPIO pins, but some power-hungry HATs (like those with motors or displays) may require a separate, external power supply. Make sure your power setup can handle the combined load of both the Pi and the HAT to avoid performance issues.
HATs are more than just simple accessories. They are fantastic tools that allow your Raspberry Pi to go even further beyond what it can do out of the box. In this tutorial we learned how HATs are able to be plug-n-play using EEPROM chips and the variety of categories and uses these boards have. You’re now well equipped for your next project and figuring out what addons you need for it! If you enjoyed this article make sure to check out the rest of our blog and socials where we post fantastic events that we attend or host! Have you ever used any of the HATs that I’ve mentioned above? Tell me about your project in the comments or submit it on our homepage so we can have a deeper look at it.
