Home Assistant launches Connect AUX-2, a $69 smart home multi-tool

Home Assistant is free, open-source software that runs your smart home from one place. "Open-source" means anyone can read and change the code. It works with devices from many brands, so a lamp, a speaker and a thermostat can talk to each other without a company cloud in the middle.

Nabu Casa is the company that makes the official Home Assistant hardware. It is one of the commercial partners of the Open Home Foundation, the group that runs Home Assistant. Money from products like this one helps pay for the foundation's work.

Nabu Casa calls it a smart home multi-tool. It does four main jobs:

• Streams audio. It plays music to older hi-fi gear, in sync with modern smart speakers.
• Controls serial devices. It sends commands to equipment through two RS-232 serial ports.
• Acts as a Bluetooth hub. It connects Bluetooth devices to Home Assistant. Home Assistant calls this a Bluetooth proxy.
• Hosts a Z-Wave adapter. You plug in a Connect ZWA-2, and the AUX-2 can sit anywhere in your house.

The box is about the size of a deck of cards. It has 2.4GHz Wi-Fi, Bluetooth, Ethernet, a USB-A port, a USB-C port, a combined digital and analog audio jack and a Grove port. A Grove port is a small plug for adding sensors and buttons.

Power over Ethernet, or PoE, sends power and data through one network cable. You can put the device anywhere you can run a cable, even where there is no outlet. The AUX-2 also runs on USB power and Wi-Fi.

Nabu Casa says PoE was the most requested feature. It also says PoE was most of the hardware cost, so adding extra ports turned out to be surprisingly cheap. That is how a simple PoE box grew into a multi-tool.

In real life Your Home Assistant computer lives in a basement. Your Z-Wave adapter plugged into it can barely reach the second floor. Move the adapter into the AUX-2, put the AUX-2 in a hallway upstairs, and run one cable.

Nabu Casa says there is plenty of overlooked audio gear that sounds great and sells cheap on local marketplaces. Much of it has two things: an optical digital audio input and a serial control port.

Optical audio sends sound as light through a fibre-optic cable. It carries clean, CD-quality sound. The serial port lets you control the volume, the source and the power, even from standby. That also lets you turn off an old device's poorly maintained smart features, which can waste energy while the device sits connected and waiting.

The AUX-2 has a DAC, a chip that turns digital audio into sound. Nabu Casa says it is a step up from the one in its Voice Preview Edition. The box senses whether the cable is analog or digital and switches the output by itself. It never uses more than a watt or two.

A tool called Music Assistant does the heavy lifting. It supports nearly every streaming service, plus your local files, and combines them into one library. A protocol called Sendspin lets speakers from different brands play in sync. You can group several AUX-2 boxes, or pair one with a HomePod or a Sonos speaker.

A serial port is an old, simple connection that sends commands back and forth. Solar inverters, TVs and receivers have had one on the back for decades. Professional control systems have relied on them for years.

Nabu Casa says you will not replace a solar inverter or a new TV just because the app is bad. With the AUX-2, you can replace the app and get your data back. Home Assistant already supports a growing list of serial devices. You get the right cable, plug it in and add the matching integration. Some devices need serial control switched on in their settings first.

There are two serial ports, so you can control two devices at once. Nabu Casa picked RS-232 because it was the most common connector on the devices it tested. Devices that use RS-485 can connect through the USB port with a $15 adapter, which also opens the door to Modbus equipment. Modbus is a common language for industrial and energy gear.

The serial ports use 3.5 mm connectors, the same size as headphone plugs. To stop people plugging in headphones, Nabu Casa put a sticker over them at the factory. Switches on the bottom let you swap the send and receive wires, so almost any cable should work without opening the box.

Z-Wave, Zigbee and Thread are wireless languages that smart home devices speak. Nabu Casa's adapters for them plug in by USB, which ties them to wherever your Home Assistant computer sits. The AUX-2 frees them.

• Z-Wave: Nabu Casa has tested this setup for months and says it works great.
• Zigbee: It works, but it is still very new. Nabu Casa is not advertising it yet and wants more testers.
• Thread: It does not work. Thread is too sensitive to delays to run reliably over a network.

Nabu Casa recommends a wired connection. Wi-Fi is possible, and its tests with the ZWA-2 show only a small rise in delay. But Wi-Fi can still be unstable, and with Zigbee it can add interference.

A standalone Thread border router, a device that links Thread gadgets to your network, is theoretically possible with a ZBT-2 and an AUX-2. It would need a big rewrite of the serial communication, and Nabu Casa says that work has not started.

Many Bluetooth gadgets act as if their own cloud hub is the only way to connect them. Nabu Casa says they often work better when connected straight to Home Assistant. The AUX-2 is its first device built just for that job.

There is no flashing and no setup. Once you add the box to Home Assistant, it starts finding Bluetooth devices in your home. It has an improved antenna. With Ethernet, Wi-Fi and Bluetooth no longer share one antenna, so Bluetooth gets a dedicated one. You can put several around the house.

A reviewer who tested it for a couple of days used it to bring Govee Bluetooth thermometers into Home Assistant and watch a garage fridge. The sensors kept their connection through three walls and a fridge.

Setup took a USB-C cable and a browser: the firmware (the built-in software that runs the device) installed from the browser, Wi-Fi details went in, and the rest was done inside Home Assistant. The reviewer did not test the serial ports.

Yes, and Nabu Casa wants you to. The AUX-2 is built on ESPHome, an open platform for making your own smart home devices from cheap boards. It is fully unlocked and ready for other firmware. Nabu Casa suggests turning it into a dedicated Squeezelite or Snapcast streamer, which are two ways to play music around a home.

The Grove port accepts GPIO and I2C sensors, which can measure temperature, humidity or light. Those readings show up in Home Assistant. Nabu Casa's example: add a $5 temperature sensor to watch the cooling of a server rack.

There are no clips or glue. Four Phillips screws hold it shut. Nabu Casa also plans to release the circuit board and 3D print files.

You could. The reviewer points out that the AUX-2 does nothing you could not do with an ESP32 board and some parts. They name the Apollo Automations Cast-1, which costs $35 and handles the same music casting and Bluetooth proxy jobs.

Nabu Casa does not hide from that. Its hardware is meant to speed up development of the software, and it says serial support has grown a lot this year. When you buy its products, you pay for that work. Anyone can still make a device of their own.

• Old gear gets a second life. An amplifier, a solar inverter or a TV with a serial port can join your smart home instead of going to the scrap heap.
• Fewer cloud apps. Bluetooth gadgets can connect straight to Home Assistant instead of through a maker's hub.
• Better wireless range. Put a Z-Wave adapter wherever a network cable reaches, not where your server sits.
• Check the fine print. Zigbee over the network is still in testing, and Thread does not work. Serial control needs the right cable and sometimes a setting turned on.