New & Reviewed

Build it With: Onion Omega2

DIYODE Magazine

Issue 7, January 2018

What’s better than a Raspberry Pi that is one-third the size of an Arduino and won’t make you cry? An Onion. An Onion Omega2, that is!

Built for IoT applications, Onion are proving increasingly popular amongst makers for their ultra-compact form factor, and powerful performance. And with it's ultra-compact form factor and solid processing power, the Onion Omega2 is a very versatile board. What's important to consider with Onion is that it's really an embedded-application powerhouse. Unlike a Raspberry Pi, there's no HDMI display, so it's not quite like a mini computer. However running Linux LEDE, it provides the functionality of a computer, reaching beyond the capabilities of a single-application Arduino too.

Rather than Onion being part of a large board to break out all the functionality, everything is available for you to hard wire. This key design consideration solves some of the challenges with “minifying” larger Arduino projects, since you’re already working with a small board. It’s then your job to build it up with the features you need, rather than scale back the features you don’t. One key benefit of this approach is if you’re integrating it into your own PCB for a specific application, there’s no “surplus” hardware taking up valuable space in your case. Since “using” your programmed device is probably going to be where the Onion lives long-term, making a programming board something of a “temporary dock” feels like a smart decision to us. Once it’s coded up there’s no excess baggage and it’s easily integrated into your hardware.

We can hear you shaking your head... “but can’t you just code up an ATmega328p too?”. Sure, yes you can. However with an Omega2, you have so much more functionality. It may not have plugs and sockets mounted to a board, but you still have a full USB 2.0 interface (can be used for expanding storage or connecting peripherals), Ethernet connection, and WiFi b/g/n to get you connected to whatever you want. These are fairly important considerations, and represent huge advantages over a similar sized Arduino Nano or similar. What’s more, you can break out those important Ethernet connections such as part of your broader hardware installation, rather than trying to “hack” the onboard connections into a case (which often limits mounting options).

In addition to the general connectivity, the Omega2 has more I/O than you can poke a stick at, and likely more than you’ll use in one application. It provides I2C, I2S (an electrical serial bus interface standard used for connecting digital audio devices together), SPI, 2 UARTS (one used by the system), and more. There’s 15 GPIO with 2 hardware PWM for fantastic interfacing capability too. The 2 x 16 header breaks out easily, and provides a U.FL connector to optionally connect an external WiFi antenna to expand your range.


We all know it’s not just about hardware, and Onion haven’t forgotten this either. Running Linux LEDE (that’s Linux Embedded Development Environment) it’s a powerful framework to bring the code language of your choice for development. Whether you come from an Arduino background with C as your preferred language, or are a Raspberry Pi fanatic and Python is your go-to, you’ll feel right at home with both options available. What’s really awesome about a Linux platform however, is the availability of virtually all languages. If you come from a web background and PHP or NodeJS is more your style, then those options are available to you too.

So while it’s difficult to compare, you get the programming flexibility of a Raspberry Pi, with the embedded intent of an Arduino. And all with the critical connectivity you need for full-scale IoT deployment - AWESOME! The Omega2 boards are 3.3V TTL, which isn’t much of an issue, but worthy of remark. Many Arduino modules will work with 3.3V or 5V anyway, and it’s a fairly simple process to step down if they don’t anyway.


It’s important to note, while we think the tiny form factor is great for deployment, we all know it’s not quite as friendly for development. But Onion have this covered as there’s a huge range of boards and docks to do all sorts of things. From a breadboard breakout (somewhat similar to the Raspberry Pi t-style breadboard breakout) to give you easily identifiable connectivity, to an Arduino shield which allows you to connect many Arduino shields to interface too. These boards often provide a USB connector, power interface, and more, to make development a snatch.


Overall we’re super impressed with the Onion Omega2 boards. We’re going to dive in and play with the OLED display and some other hardware supplied, so keep an eye out for an update on these too.

Onion have gone to great lengths to provide clear documentation to all prudent resources, and the community around the products is building.

What's Inside?

Inside both Onion Omega2 models, you’ll find a powerful 580MHz processor, to grind out those computations. In each Omega2 you’ll also find USB 2.0, WiFi, Ethernet, SPI, I2S, I2C, UART, and 15 GPIO with 2 PWM.

There are two flavours of the Onion Omega2 depending on your taste (okay, that’s enough food puns, but we couldn’t resist). Most functionality is identical (and both run Linux) but the Omega2 Plus has a little extra potential. Here are the differences compared:

Omega2:Omega2 Plus:

For more information check out

The Onion Omega2 and additional accessories are available at Core Electronics