Category: Raspberry Pi

Hardware Attached on Top (HAT) and add-on boards for Raspberry Pi

Transform Wii Nunchuk into a USB-C Joystick for Your PC with ANAVI Handle


Let’s explore how to retrofit a classic Wii Nunchuk controller using ANAVI Handle, an open source hardware USB-C adapter that lets you connect a wired Nunchuk controller to any modern PC, be it a laptop or desktop. In this tutorial, you will learn how to configure the Nunchuk as a joystick and enjoy the open-source game “Tiny Crate”, all within your web browser.

Hardware Requirements

To get started, you’ll need:

  • A personal computer
  • A USB Type-C cable
  • An ANAVI Handle along with a Wii Nunchuk (or another compatible controller)

Software Configuration

Begin by connecting your Wii Nunchuk controller to your computer using the ANAVI Handle, an open-source hardware adapter. Next, edit the config.json file to enable joystick mode by adding:

{
    "type": "joystick"
}

The ANAVI Handle’s default open-source firmware (written in CircuitPython) uses the analog stick and buttons on the Nunchuk to control movement in joystick mode. After modifying config.json, disconnect and reconnect the ANAVI Handle to apply the changes.

The ANAVI Handle’s RGB LED provides visual feedback on the connection status:

  • A green light indicates a successfully connected Nunchuk controller.
  • A blue light shows the controller has been disconnected from the ANAVI Handle.
  • A red light signals an absent or improperly connected Nunchuk controller.

In the video, you’ll see the green light illuminated, confirming that everything is functioning correctly.

To quickly verify that your controller is working in joystick mode, load the HTML5 Gamepad Test in a modern web browser. This open-source tool is available on GitHub under the MIT license and provides a simple way to check your controller’s functionality.

Let’s Play!

Once everything is set up, you’re ready to dive into games that support joysticks!

While preparing this video, I discovered an incredible game called Tiny Crate. It’s a 2D puzzle game with charming pixel art graphics and joystick compatibility. Despite being a puzzle game, its game play evokes a sense of nostalgia for classic jump-and-run titles. Tiny Crate is an open-source game, with its source code available on GitHub. Developed using the Godot game engine, it’s playable on multiple platforms including Windows, macOS, Linux, and even Android.

I featured Tiny Crate while demonstrating the ANAVI Handle during the “Show and Tell” segment of Pi Wars, a Raspberry Pi-based, non-destructive robotics competition. Pi Wars 2024 took place on April 20th-21st in Cambridge, UK, attracting 58 teams of robot engineers. During my demonstration, children of all ages were captivated by Tiny Crate, so much so that many were too absorbed in solving game levels to notice the ANAVI Handle or the Nunchuk controller. This speaks volumes about the quality of Tiny Crate and the effectiveness of the ANAVI Handle in seamlessly converting the Nunchuk controller into a USB HID device.

If you’re passionate about gaming innovation and eager for a new experience, all you need is a Nunchuk controller and an ANAVI Handle. After a successful crowdfunding campaign ANAVI Handle is available at Crowd Supply. We will soon stock it at our other distributors. Follow this guide and get ready to enjoy hours of fun with your favorite games!

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Classical Gaming on a PC with RetroPie and Nintendo Wii Nunchuk Controller

Thanks to open source it is possible to enjoy your favorite arcade, home-console, and classic PC games on a budget setup. In this video tutorial, we will transform an old netbook into a portable retro-gaming machine using Raspberry Pi OS and RetroPie.

RetroPie is a software package designed to enable the emulation of classic video game consoles that sits on top of a full OS. In this tutorial we will install it on top of a Linux distribution. RetroPie allows users to play games from a wide range of vintage systems by using emulators for platforms such as:

  • Atari 2600, 5200, 7800, Lynx
  • Commodore 64
  • Nintendo Entertainment System (NES), Super NES (SNES), Nintendo 64 (N64), Game Boy, Game Boy Advance
  • Sega Genesis/Mega Drive, Sega CD, Sega 32X, Sega Master System, Game Gear
  • Sony PlayStation 1

Required Hardware

This is the required hardware for this tutorial:

  • Personal computer (PC). For example an old netbook like Acer Aspire One D257 or Asus EeePC (or similar) with an Intel Atom or AMD CPU is a great fit.
  • ANAVI Handle open source hardware USB adapter for Wiimote attachments
  • Wii Nunchuk controller (or another compatible controller)

Software

Follow the steps below to install and configure all the required software on your computer.

Step 1: Install Raspberry Pi OS for Desktop

Raspberry Pi Desktop for PC and Mac is a 32-bit GNU/Linux operating system designed for older and less powerful computers. It’s based on Debian, a popular Linux distribution, and includes the Raspberry Pi OS desktop environment along with a set of recommended software. If you have an aging computer that can’t handle modern commercial operating systems, Raspberry Pi OS can revitalize it, making it usable again. To get started, download the OS, flash the ISO file onto a USB drive, boot from the USB on your computer, and proceed with the installation.

Step 2: Install RetroPie

Follow the official documentation for installing RetroPie on a PC running Debian or Ubuntu. Use the RetroPie setup script to perform a Basic Install.

Step 3: Transfer ROM files

After RetroPie is installed, you’ll need to move ROM files for your favorite games into the correct directories. If you followed the steps above, the main directory for all ROMs is located at ~/RetroPie/roms (or /home/pi/RetroPie/roms, which is the same). There are subdirectories for each supported emulated system, such as NES, SNES, and others.

Step 4: Connect ANAVI Handle and Nunchuk

The next step is to connect a Wii Nunchuk controller to your computer using our open-source hardware adapter. Edit config.json and enable keyboard mode:


{
    "type": "keyboard"
}

ANAVI Handle comes with open source firmware written in CircuitPython. The keyboard mode includes a D-pad (directional pad, aka arrows), along with A and B keys. Save the changes to config.json. Ensure they take effect by disconnecting and then reconnecting the ANAVI Handle. After that configure the controls in RetroPie using the Nunchuk controller and ANAVI Handle.

The RGB LED on ANAVI Handle indicates the connection state

Connection States Through RGB LED

The default open-source firmware uses the RGB LED to display three different connection states:

  • A green light means the Nunchuk controller is properly connected.
  • A blue light indicates the controller has been disconnected from the ANAVI Handle.
  • A red light warns that the Nunchuk controller is missing or not connected correctly.

In the demo video, you’ll see the green light on, signaling that you’re ready to enjoy some classic games!

Enjoy Retro Gaming on the Go

Once everything is set up, you can begin your retro-gaming adventure! Power on your computer. RetroPie will start automatically (unless you’ve configured it differently), allowing you to dive into a world of classic arcade, home console, and homebrew games. Whether you’re fighting aliens or challenging a heavyweight champ, a whole world of gaming awaits you. heavyweight champ, a whole world of gaming is waiting for you.

If you have an old Netbook, give it a second chance as portable gaming machine! Get a Nunchuk controller and our open source ANAVI Handle, follow this tutorial, and get ready to relive the golden age of gaming!

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ANAVI Arrows and ANAVI Macro Pad 12 Are Open Source Hardware Certified

The ANAVI Macro Pad 12 and ANAVI Arrows have received official certification from the Open Source Hardware Association (OSHWA). OSHWA, a non-profit organization based in the United States, manages the Certified Projects Directory and hosts the annual Open Hardware Summit. Notably, the summit takes place in different cities, and in 2024, it is scheduled to be held in Montreal, Canada.

The printed circuit boards of ANAVI Macro Pad 12 and ANAVI Arrows were designed the open source software KiCad

The certification program by OSHWA ensures that a project’s understanding of “open source hardware” is in harmony with the wider community’s definition of open source hardware. Subsequently, OSHWA assigns a unique identification number (UID) to every certified hardware version. This UID commonly comprises a blend of a country code and a numerical sequence, ensuring that each certified hardware version possesses a distinct identifier. For our two new keyboards, the UIDs are:

BG000094 for ANAVI Arrows version 1.0
BG000095 for ANAVI Macro Pad 12 version 1.0

The OSHW Certification Mark serves a dual role: not only does it display the project’s unique certification ID, but it also streamlines navigation and information retrieval. In this context, the “BG” prefix signifies the country code for Bulgaria, indicating that these mechanical keyboards are crafted in Plovdiv, the second-largest city in Bulgaria and the oldest continually inhabited European city with over 6000 years of history. What sets our keyboards apart is their complete adherence to open-source principles. This means that every facet of their design and functionality is open and freely accessible to everyone. Our dedication to openness extends to utilizing only free and open source software in various project aspects, including designing the printed circuit board, creating acrylic enclosures, developing firmware, and thoroughly documenting the entire process.

The printed circuit boards for ANAVI Arrows and ANAVI Macro Pad 12 were designed with the open source software KiCad on Ubuntu Linux distribution. Furthermore, we use open source firmware called KMK, written in CircuitPython. Soon QMK firmware will be also ported to both keyboards. Open source ensures transparency, sharing knowledge and hopefully fostering collaboration and innovation within the community.

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Mastering Gesture Recognition with Raspberry Pi and APDS9960 Low-Cost Sensor

In the world of electronics and IoT, gesture recognition has emerged as a fascinating and practical technology. Whether it’s controlling your favorite gadgets with the wave of a hand or adding a touch of magic to your projects, gesture recognition sensors play a pivotal role. Among the numerous sensors available, the APDS9960 stands out as a versatile and widely used I2C sensor at a very affordable price. In this blog post, we will take you on a journey through the fascinating world of gesture recognition using the APDS9960 sensor on a Raspberry Pi and any of our popular add-on boards: ANAVI Infrared pHAT, ANAVI Light pHAT, ANAVI Gardening uHAT, ANAVI Info uHAT as well as ANAVI Miracle uHAT and ANAVI CO2 uHAT (both of which are in final development).

What is APDS9960?

APDS9960 is an I2C (Inter-Integrated Circuit) sensor produced by Broadcom (formerly Avago Technologies). It is known for its versatility and is commonly used for gesture recognition, proximity sensing, ambient light sensing, and color sensing applications. Gestures are detected at a distance of 10 to 20 cm. The sensor has built-in UV and IR filters for better recognition. Its wide range of applications makes it a favorite choice among electronics enthusiasts, engineers, and hobbyists. Ovewr the years APDS9960 has been integrated in many popular consumer electronic devices, including Samsung Galaxy S5 smartphone.

In this tutorial, we will explore how to set up gesture detection on a Raspberry Pi running the Raspberry Pi OS Linux distribution. Specifically, we will use the APDS9960 I2C sensor connected to a Raspberry Pi uHAT (add-on board) and a mini OLED SSD1306 I2C yellow-blue display.

BH1750 I2C light sensor attached to ANAVI CO2 uHAT and a Raspberry Pi single board computer running GNU Linux distribution

🔌 Hardware Setup

Both APDS9960 sensor and the mini yellow-blue SSD1306 OLED display rely on the serial communication protocol I2C that allows multiple electronic devices to communicate with each other using only two wires: serial data (SDA) and serial clock (SCL). Raspberry Pi single board computers have two different I2C busses. The primary I2C bus is at GPIO 2 (physical pin 3 for SDA) and GPIO3 (physical pin 6 for SCL). These pins should be used to attach APDS9960 and the mini OLED display to the Raspberry Pi. Also APDS9960 should be connected to 3.3V and GND pins of the Raspberry Pi to be powered. This makes 4 wires in total to attach the sensor. ANAVI HATs (Hardware Attached on Top) for Raspberry Pi offer dedicated slots for I2C sensors. On ANAVI Info uHAT and ANAVI CO2 uHAT there are even dedicated slots for the mini OLED display.

Of course the OLED display is optional and as an alternative we offer a simple command-line Python3 example for APDS9960 which can function without the OLED display.

🖥️ Software Setup

The software setup is straight forward: install Raspberry Pi OS on microSD card, boot your Raspberry Pi and enable I2C using raspi-config. More details are available in the user’s manual for our HATs.

🐍 Python3 Scripts

The heart of our demonstration are scripts written in the Python 3 programming language. We’ve tailored the script to work seamlessly with Raspberry Pi OS, but it should also run smoothly on any other GNU Linux distribution. These scripts rely on popular Python3 libraries like PIL and Luma OLED. You can find the source code on GitHub for reference and further experimentation:
https://github.com/AnaviTechnology/anavi-examples/tree/master/sensors/APDS-9960/python

There are two different Python 3 scripts to demonstrate APDS9960 gesture detection:

  • gesture-oled.py for detecting gestures and showing them on the mini OLED display as in the video
  • gesture.py for detecting gesture and printing them in the command-line interface (use this one if don’t have a suitable mini OLED display)

👁️ Real-Time Gesture Detection

Experience the magic as the APDS9960 sensor detects your hand movements, including swipes, taps, and more. Witness how your Raspberry Pi interprets and responds to these gestures in real-time, opening up a world of interactive possibilities. The video provides insights into potential issues you might face during setup and offers practical tips to ensure a seamless experience.

🎓 Conclusion

APDS9960 sensor and Raspberry Pi combination offer a compelling glimpse into the exciting world of gesture-based interaction. Instead of using a breadboard and multiple wires it is always easier to rely on one of our add-on boards like ANAVI Infrared pHAT, ANAVI Light pHAT, ANAVI Gardening uHAT, ANAVI Info uHAT, ANAVI Miracle uHAT and ANAVI CO2 uHAT.

So, if you are ready to embark on this exciting journey into gesture recognition technology, grab your Raspberry Pi, APDS9960 sensor, and let’s get started!

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ANAVI Macro Pad 12 and ANAVI Arrows: Manufacturing Progress

After our crowdfunding campaign concluded successfully, we immediately started the manufacturing phase without delay. Thankfully, we had the foresight to ensure we had all the necessary components in stock ahead of time. Just recently, we happily received the first batch of ANAVI Arrows and Macro Pad 12 printed circuit boards, which are adorned with surface mount components on both sides.

ANAVI Arrows and ANAVI Macro Pad 12

We are already in the process of locally producing our second batch, and we expect it to be ready by the end of September. These printed circuit boards are meticulously gold-plated to guarantee the highest quality.

XIAO module with Raspberry Pi RP2040 assembled on the mini mechanical keyboard ANAVI Arrows

Additionally, the acrylic enclosures were laser cutted in August. Our next steps include programming CircuitPython and the KMK firmware, testing, and packaging all keyboards.

Once again,thank you for your support of ANAVI Macro Pad 12 and ANAVI Arrows. Stay tuned for more exciting updates in the coming weeks!

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Understanding I2C: Exploring OLED Displays and Peripherals on Futuristic Mechanical Keyboards

I2C (Inter-Integrated Circuit) is a popular serial communication protocol that allows multiple integrated circuits to communicate with each other over a short distance, typically limited to a few meters. Each device on the bus has a unique address, identifying it and allowing it to communicate individually. The protocol was developed by Philips (now NXP Semiconductors) in the 1980s. Over the years it has become a standard for communication between various electronic components in embedded devices. I2C can be used to connect various peripherals, such as sensors, displays and EEPROMs. The mini OLED yellw-blue displays on our compact mechanical keyboards ANAVI Macro Pad 12 and ANAVI Arrows are connected to the Raspberry Pi RP2040 microcontrollers over I2C.

ANAVI Arrows and ANAVI Macro Pad 12 are open source mechanical keyboards with mini OLED I2C displays

I2C is easy to use becase it requires only two wires for communication:

  • SDA (Serial Data) for transmitting and receiving data between devices
  • SCL (Serial Clock) for a clock signal to synchronizes the data transfer between the devices

The core component of our hot-swappable mechanical keyboards ANAVI Macro Pad 12 and ANAVI Arrows is Seeed Studio XIAO RP2040 module. This is actually a tiny development board suitable for surface-mount technology (SMT) assembly and equipped with a Raspberry Pi RP2040 32-bit dual-core ARM Cortex M0+ MCU, 264 KB SRAM, 2 MB Flash memory, 11 GPIO pins and USB-C connector. The I2C interface is located on pins D4 (for SDA) and D5 (for SCL) of XIAO RP2040.

Seeed Studio XIAO RP2040 module on ANAVI Macro Pad 12 mechanical keyboard

A yellow-blue mini OLED I2C display is included in all kits with ANAVI Macro Pad 12 and ANAVI Arrows. It has 4 pins: GND (ground), VCC (supply voltage), SCL, and SDA. This display relies on SSD1306, a single-chip CMOS OLED/PLED driver with controller for organic / polymer light emitting diode dot-matrix graphic display system which consists of 128 segments and 64 commons. It is the same display we include in our other mechanical keyboards like the ANAVI Macro Pad 10 and ANAVI Macro Pad 8, Internet of Things devices like the ANAVI Thermometer and ANAVI Gas Detector, tools like ANAVI Fume Extractor, and Raspberry Pi add-on boards like ANAVI Info uHAT. This versatile mini OLED display is a great fit for many projects, You can pick one up at Mouser if you need a spare.

Mini yellow-blue 0.96″ OLED display attached to ANAVI Macro Pad 12 with QMK firmware for mechanical keyboards

There is a dedicated slot for the display on the printed circuit board. Just plug the mini OLED display into it and then connect the mechanical keyboard to a computer. In every kit with ANAVI Macro Pad 12 and ANAVI Arrows, you will find four additional male-to-female jumper wires included, providing you with an exciting opportunity to get creative with your project. If you decide to design your own 3D printed case for the keyboard, these jumper wires may become handy. They grant you the flexibility to reposition the mini OLED display to a location of your choice within the case.

ANAVI Macro Pad 12 is compatible the two most popular open source firmwares for mechanical keyboards: KMK and QMK. KMK is written in CircuitPython and QMK in the C programming language. Both support OLED displays over I2C.

Out of the box ANAVI Macro Pad 12 and ANAVI Arrows come with the KMK firmware. It uses the extension Peg Oled Display based on the open source CircuitPython libraries Adafruit_CircuitPython_DisplayIO_SSD1306 and Adafruit_CircuitPython_Display_Text. This extension allows your keyboard to display images or text and even to react to the currently selected keyboard layer.

ANAVI Macro Pad 12 with a breadboard and additional I2C peripherals

Makers with advanced skills have a fantastic opportunity to extend the capabilities of the keyboard project by adding more I2C peripherals. Using a breadboard and without any soldering, makers can easily connect additional I2C peripherals, such as sensors or other modules that communicate via I2C, to the existing setup. This allows them to expand the project’s functionalities and explore various creative ideas. Those seeking a more permanent and tailored extension can even design their own custom I2C add-on printed circuit board. The mini OLED displays included in the kits work out of the box, but it is important to be aware that incorporating any other I2C devices into the keyboard will require adjusting the KMK firmware to support the additions.

Support our crowdfunding campaign and get the open source mechanical keyboards ANAVI Macro Pad 12 and ANAVI Arrows with a mini OLED display for real-time notifications and customizable graphics at your fingertips. Learn how to use I2C and unleash your creativity by extending the keyboard with additional peripherals!

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KMK: Harnessing the Potential of Open Source and CircuitPython to Energize Mechanical Keyboards

Within the realm of computer keyboards, a remarkable open-source firmware called KMK has surfaced, captivating enthusiasts from all corners. KMK possesses a potent capability to revolutionize mechanical keyboards into personalized instruments, enabling users to venture into uncharted territories of customization and productivity.

KMK Open Source Mechanical Keyboard Firmware Written in CircuitPython

CircuitPython is an open-source programming language that runs on microcontrollers used in various embedded applications, including mechanical keyboards like ANAVI Macro Pad 12 and ANAVI Arrows from our crowdfunding campaign at Crowd Supply. Built upon the foundations of Python, CircuitPython is specifically crafted to cater to the requirements of resource-limited embedded devices housing microcontrollers. One of the standout merits of CircuitPython lies in its user-friendly nature and effortless adaptability, particularly beneficial for newcomers who may not possess extensive coding expertise.

ANAVI Arrows and ANAVI Macro Pad 12 with the open source firmware KMK written in CircuitPython

The source code of KMK is readily available on GitHub, released under the GPLv3 license. The inception of KMK can be traced back to 2018. Notably, the KMK source code follows a coding style that employs the Python code formatter, known as Black, and embraces the usage of single quotes.

KMK firmware runs on Raspberry Pi RP2040 microcontoller which is in the core of Seeed Studio XIAO RP2040 module

The hardware requirements for microcontrollers to run KMK are: a minimum of 256KB of flash storage, support HID over USB and/or Bluetooth, CircuitPython version 7.0 or newer. With its impressive hardware capabilities, the Raspberry Pi RP2040 microcontroller is a perfect fit for CircuitPython and KMK. Because of this we selected Seeed Studio’s XIAO module with RP2040 for ANAVI Macro Pad 12 and ANAVI Arrows.

KMK offers many key features:

  • Key Mapping: Customize key assignments to suit individual preferences
  • Macros: Create and assign macros for automating tasks or executing commands
  • Layers: Define multiple virtual layers for accessing different functions or modes
  • LED Control: Customize backlighting and LED behavior
  • Rotary Encoder: Rotary encoders for various functions like volume control or scrolling.
  • Mini OLED Display: Compatibility with mini OLED displays, allowing users to display custom information or visuals on their keyboards
Back-light and under-light effects with KMK firmware on the mechanical keyboards ANAVI Macro Pad 12 and ANAVI Arrows

KMK supports many mechanical keyboards, including ANAVI Macro Pad 12 and ANAVI Arrrows. Although you are free to change to another firmware at any time, both ANAVI Macro Pad 12 and ANAVI Arrrows out of the box will come with KMK pre-installed.

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ANAVI Macro Pad 10 & Knobs are Funded!

The launch of our crowdfunding campaign was a blast! ANAVI Macro Pad 10, ANAVI Knobs 3, and ANAVI Knob 1 were all fully funded and all stretch goals were met in the first week. Thanks to all backers and Crowd Supply for bringing life to these three entirely open source projects!

As part of the covered stretch goals, each kit will include stickers from ANAVI Technology and KiCad, the free and open source CAD software used for designing the printed circuit boards of the keyboards. Furthermore, ANAVI Macro Pad 10 kits will include 32 super-cool emoji stickers. You can stick them on the top or sides of the translucent keycaps. Last but not least, we’ll be publishing various video tutorials to ensure getting started is easy.

One more thing… Recently, our mini mechanical keyboards were featured in an article by CNX Software. This is a very popular website with news and tutorials about embedded systems, makers, and open source hardware. It was started in 2010 by Jean-Luc Aufranc. By the way it is worth keep an eye on CNX Software because there are always news about interesting gadgets!

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ANAVI Macro Pad 10 and Knobs Coming Soon

With Crowd Supply we are preparing a new crowdfunding campaign for 3 open source hardware mechanical keyboards: ANAVI Macro Pad 10, ANAVI Knobs 3 and ANAVI Knob 1.

ANAVI Macro Pad 10, ANAVI Knobs 3 and ANAVI Knob 1

There are many common things between these 3 mini mechanical keyboards:

  • Seeed XIAO RP2040 – a power module with USB-C and Raspberry Pi RP2040 MCU from Seeed Studio
  • Rotary encoders
  • KMK – an open source firmware for mechanical keyboards written in CircuitPython
  • Open source hardware designed with the free and open source software KiCad

Subscribe at our pre-launch page at Crowd Supply to be the first to know when we launch the crowdfunding campaign!

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Exploring I2C buses on ANAVI Info uHAT

I2C stands for Inter-Integrated Circuit, pronounced eye-squared-C, and alternatively known as IIC. It is a synchronous, multi-controller/multi-target (controller/target), packet switched, single-ended, serial communication bus. This protocol is suitable for devices wired at short distances, no more than 2-3m. We use I2C in pretty much all our open source products: Internet of Things, mechanical keyboards and Raspberry Pi HATs.

Anavi Info uHAT
I2C sensor modules attached to ANAVI Info uHAT

I2C was originally developed in 1982 by Philips. While that makes it 40 years old, it is still a very convenient and widely used bus. There are many I2C sensors and peripherals. It is in pretty much every smartphone, embedded electronics, microcontroller, personal computer and of course Raspberry Pi.

ANAVI Info uHAT with 4 slots for I2C sensors and mini OLED dsiplay

Actually, since the introduction of the famous 40-pin header in 2014, Raspberry Pi single board computers have not one but two I2C buses! We use them both on ANAVI Info uHAT and our other HATs. Th first I2C bus is on pins 3 and 5. On the ANAVI Info uHAT, it is used for the three I2C slots for sensors and the 4th dedicated slot for the mini OLED display.

The I2C bus on ANAVI Info uHAT in KiCad’s Schematic Layout Editor.

The second I2C bus is on pins 27 and 28 of the Raspberry Pi and is reserved exclusively for attaching an ID EEPROM. The ID EEPROM contains a software description of the hardware so the operating system on your Raspberry Pi can automatically identify the add-on board.

The EEPROM on ANAVI Info uHAT attached on the 2nd I2C bus

The I2C bus consists of two signals: SDA (Serial Data) is a data signal, SCL (Serial Clock) is a clock signal. I2C modules also need power, so the dedicated I2C connectors on the ANAVI Info uHAT and our other open source hardware provide two additional pins for VCC and GND. Typically, the VCC for the I2C connectors on our add-on boards for Raspberry Pi are 3.3V.

The I2C bus drivers are “open drain”, which means they can only pull the corresponding signal line at low level. They cannot drive it high. To restore the signal to high when no device is asserting it low, a pull-up resistor has to be added to each signal line. For example, on the ANAVI Info uHAT, we have 4.7K pull-up resistors R4 and R5 connected to SDA and SCL.

Resistor selection varies depending on the devices attached to the bus. In some specific use cases, further adjustment of the resistance value might be required. For systems with lots of devices or longer wires, smaller resistors are better.

How to Enable I2C on Raspberry Pi OS

Raspberry Pi OS, previously known as Raspbian, is the default and recommended Linux distribution for all models and versions of the Raspberry Pi single board computer. By default, I2C is not enabled. There are several ways to enable it, but probably the easiest is using the command-line tool raspi-config to perform few basic commands:

  • Open a terminal or login remotely via SSH to your Raspberry Pi and type in the following command: sudo raspi-config
  • Select Interfacing Options > I2C and enable it
  • Reboot the board

More details are available in the user’s manual for the ANAVI Info uHAT.

I2C Addresses

Each I2C device must have a unique address. The I2C reference design has a 7-bit address space, although rarely it might be used with a 10-bit extension. The 7-bit addresses range from 0 to 127 (0 to 0x7F hexadecimal). This is a limitation because it is not possible to have two I2C devices with the same address on the same I2C bus. For example, the I2C address on the mini OLED display included in all ANAVI Info uHAT kits is 0x3C. From the software side, this address is used in the example Python 3 script to access the display.

Python3 script controlling the mini OLED display over I2C on ANAVI Info uHAT

For Linux distributions, including Raspberry Pi OS, there is a package with a heterogeneous set of I2C tools called i2c-tools. To install it on Raspberry Pi OS, open a terminal and execute: sudo apt install -y i2c-tools. Once you have it installed, you can list attached I2C devices by their addresses with i2cdetect. For example, if the HTU21 temperature and humidity sensor module is attached to the Raspberry Pi, the output will be:

pi@raspberrypi:~ $ sudo i2cdetect -y 1
     0  1  2  3  4  5  6  7  8  9  a  b  c  d  e  f
00:                         -- -- -- -- -- -- -- --
10: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
20: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
30: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
40: 40 -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
50: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
60: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
70: -- -- -- -- -- -- -- --

I2C Sensors and Peripherals

I2C Sensors and Peripherals

ANAVI Info uHAT officially supports the following I2C devices:

  • Mini OLED SSD1306 0.96″ display
  • HTU21D sensor for temperature and humidity
  • BH1750 sensor for light
  • BMP180 sensor for barometric pressure

Some of the other popular I2C sensor modules in maker community include:

  • APDS-9960 sensor for RGB color and gesture detection
  • BME680 for temperature, humidity, pressure and gas sensor
  • MCP9808 for temperature
  • MPL115A2 for barometric pressure
  • ADT7410 for temperature
  • MPU-6050 for triple axis acccelerometer and gyroscope

Which is your favorite I2C device? Join the discussion and let us know on Twitter!

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