Nabu Casa, the commercial part of the Open Home Foundation, which runs Home Assistant, has just launched the Home Assistant Connect Aux-2, a multifunction box designed to help you add more non-smart devices to your smart home. It’s part of Home Assistant’s ongoing efforts to be easier to use. And it’s working.
I’ve been testing the Aux-2 for a couple of days and, as expected, found it useful and surprisingly easy to set up. The Aux-2 is a $69 box the size of a deck of cards. It has 2.4GHz Wi-Fi, Bluetooth, Ethernet, USB-A, USB-C, a digital/analog audio jack, a Grove port for interacting with peripherals like sensors, buttons, and LEDs, and a pair of RS-232 serial ports.
You can connect Bluetooth devices with Home Assistant settings. Its USB port allows you to connect a Nabu Casa Z-Wave or Zigbee antenna in case your Home Assistant hub is not in a good location. You can control devices such as TVs, AV receivers, solar inverters and more via the serial connector. And you can connect an amplifier or powered speakers to its audio jack to stream music to older audio equipment.
All of these things take advantage of Home Assistant’s capabilities as an open source platform. The Aux-2 is based on ESPHome, an open platform for making DIY smart home devices from flexible and affordable ESP boards, and uses existing Home Assistant/ESPHome integrations for all its functions. Serial integration was developed earlier this year; Music Assistant and SendSpin, which power the audio output feature, are in active development.
I have a Home Assistant setup, but even after several years it is not my main smart home platform simply due to friction and time constraints. Instead, I have a hodgepodge of Google Home, Apple Home, and a few devices that are only on Home Assistant. The situation is not ideal.
But the Aux-2’s capabilities intersect perfectly with two things I intended to do anyway, one of which I’m already using Home Assistant for. First, I have a refrigerator in the garage because I live in Texas. I also have children, which means that sometimes the refrigerator or freezer door is left open. I want to know when that happens before all my food goes bad.
A couple of years ago, I set up some Aqara temperature sensors, connected them to Home Assistant via a now-discontinued Zigbee dongle, and set up automation to alert me if the refrigerator or freezer gets too hot. But they frequently lose connection (probably because they’re inside a refrigerator in the garage), chew up coin-cell batteries, and don’t have screens, which means I also keep a cheap Acu-rite hygrometer in the refrigerator so I can check the temperature without taking out my phone. Someone told me about Govee’s Bluetooth hygrometers, but I would need a Bluetooth proxy to connect them to Home Assistant. That’s a feature of the Aux-2.
I also have a pair of in-wall speakers in my living room that I’ve never used. I had intended to buy an amplifier, but analysis paralysis occurred. Will I receive a Wiim amplifier? A stereo receiver? A cheap Bluetooth amplifier? Do I try to get them to work with my four Sonos speakers? Maybe my old Google Home speaker? It turns out that I don’t do anything for five years. Maybe Aux-2 can help.
Setting up the Aux-2 was much easier than I expected. I connected it to my computer via USB-C and was able to download and install the latest firmware directly from a browser. I could also add my Wi-Fi credentials. I then unplugged it, moved it to my media console and plugged it into power (requires USB-C or Power over Ethernet) and did the rest of the setup in the Home Assistant interface.
In HA, I was prompted to install ESPHome, which discovered the Aux-2 and sent me to a “config your ESPHome device page” that walked me through the capabilities. Enabling the Bluetooth proxy required a couple of clicks; I added Govee Bluetooth integration, put batteries in the sensors and they appeared automatically. Fortunately, they kept their Bluetooth connection through three walls and a refrigerator, and now my refrigerator’s monitoring settings are working again.
The audio capability took a little longer, but most of it was spent connecting the speakers to the amplifier I ended up purchasing and setting up Music Assistant, which I didn’t have installed. Music Assistant sits on the Home Assistant hardware and can play from many different services, from Spotify to YouTube Music, local files and more, and to There are many different outputs, such as Sonos, Wiim, AirPlay, Google Cast and others, but you need to set them all up, and that took a bit of time. It’s not a lot of time: less than half an hour in total.
I can now play music on the in-wall speakers using Music Assistant. Sendspin, the whole-home audio standard (also developed by the Open Home Foundation), is supposed to let you group together speakers of different protocols under certain conditions, but I haven’t gotten around to it yet. The standard is still in development and I’ve been busy too, so I’m not sure if it’s my problem or theirs.
I’d also like to see the Aux-2 appear as an AirPlay or Spotify Connect target, which (again) is probably just something I need to configure.
Serial control is the Aux-2’s most intriguing feature, and unfortunately, it’s the one I haven’t had time to test yet. But the ability to connect things like solar inverters, TVs, and receivers is fascinating and I want to delve deeper when I get the chance. Maybe I’ll connect it to my LG TV.
The Aux-2 doesn’t do anything you can’t already do with an ESP32 board and various accessories, or even other ESP-based devices. The Apollo Automations Cast-1, for example, costs $35 and supports the same music streaming and Bluetooth proxy features that I’m using from the Aux-2 right now. You could create something even cheaper with DIY parts.
That’s not a knock against Aux-2. that’s all spot. The ecosystem is open by design, which I find endlessly refreshing. Both Nabu Casa and Apollo fund the Open Home Foundation, which develops Home Assistant and ESPHome (and Sendspin and Music Assistant), and both provide hardware that’s a little easier to use than DIY options. But nothing stops you from creating your own devices. It is actively encouraged.
I bought a three-pack of ESP32 boards for $16 three years ago. I could have built a Bluetooth proxy out of one of those. I could have built an LED driver. I could have built a soil sensor, a media player, or any of a dozen other things. I didn’t do anything at all.
But now that I’ve used the Aux-2 and dipped my toe into the ESPHome waters, maybe willpower.
