Home Assistant Connect Aux-2 Adds Legacy Gear for $69

The Home Assistant Connect Aux-2 has officially launched for $69, arriving as a compact hardware bridge from Nabu Casa designed to pull offline and legacy appliances into a unified smart home. Powered by ESPHome, its defining capability is acting as a versatile multi-tool that handles Bluetooth proxying, networked audio streaming, and RS-232 serial control right out of the box. It is tailored for Home Assistant users who want to link older electronics and distributed sensors without soldering their own microcontrollers, though early adopters should note that software features like SendSpin multi-room grouping remain works in progress, and the hardware carries a premium over basic DIY alternatives.

A Deck-of-Cards Hardware Bridge for Local Control

About the size of a deck of cards, the Aux-2 is built to solve the physical gaps in smart home installations. Instead of forcing users to relocate their primary Home Assistant server or assemble separate microcontroller projects, the Aux-2 packages standard wired and wireless connectivity into a neat plastic enclosure. It features 2.4GHz Wi-Fi, Bluetooth, an Ethernet port with Power over Ethernet (PoE) support, USB-C for power and flashing, and a USB-A port that can host a dedicated Z-Wave or Zigbee coordinator antenna.

For specialized hardware integration, the front panel hosts a 3.5mm digital/analog audio output jack, a Seeed Studio Grove port for attaching external environment sensors or LED indicators, and dual RS-232 serial ports hidden behind protective warning stickers. This port array turns the unit into a localized endpoint that can sit inside an AV cabinet, a utility closet, or near off-grid appliances while communicating back to your main server over the local network.

Reviving Cold Sensors and Inactive Audio Systems

Hands-on testing shows how quickly the Aux-2 resolves everyday connectivity headaches. In practical deployment, configuring the box as a Bluetooth proxy takes just a few clicks in the ESPHome integration interface. In one test environment, standard Zigbee temperature monitors placed inside a detached garage refrigerator suffered frequent disconnects through heavy walls and metal doors. Replaced with Bluetooth hygrometers routed through the Aux-2 proxy, the sensors maintained reliable signal transmission across three walls, restoring automated temperature alerts without needing a dedicated Zigbee repeater.

The built-in audio output addresses another common enthusiast dilemma: dormant analog audio gear. By connecting the Aux-2 to a standalone amplifier driving passive in-wall speakers, the device acts as a networked media player via Music Assistant. Music Assistant runs directly on the Home Assistant host, delivering playback from streaming sources like Spotify and YouTube Music as well as local libraries. While broad platform support like native AirPlay or Spotify Connect targeting requires additional setup, basic casting functioned within thirty minutes of unboxing.

Serial Connectivity and the DIY Value Equation

The most distinctive technical feature on the Aux-2 is its twin RS-232 serial interface. While many modern smart devices rely on cloud APIs, legacy home theater receivers, select smart TVs, and residential solar inverters still use robust, local serial protocols. Through Home Assistant’s recent serial proxy integrations, the Aux-2 allows users to send direct commands to hardware that lacks native network capabilities, bypassing cloud latency and deprecation risks entirely.

From a hardware standpoint, the Aux-2 does not perform tasks impossible on standard DIY microcontrollers. Enthusiasts can purchase bare ESP32 development boards for under ten dollars or opt for focused pre-built devices like the $35 Apollo Automations Cast-1, which provides similar Bluetooth proxying and audio casting. However, the $69 Aux-2 bundles PoE support, serial transceivers, multiple power configurations, and commercial manufacturing into a single plug-and-play package that directly funds the Open Home Foundation’s ongoing software development.

For smart home builders balancing limited free time against the desire for local, private control, the Aux-2 substantially reduces setup friction. It bridges the gap between raw breadboards and locked-down commercial hubs, proving that practical utility often matters more than raw DIY cost efficiency.

Have you integrated legacy audio equipment or serial devices into your smart home, or do you prefer building custom ESP32 nodes from scratch? Share how you balance convenience against DIY hardware in your setup.