100% Local, 0% Cloud: A Privacy-First Brain for Your Google Home Mini

When choosing a smart speaker for your home, there are two main options: buy an off-the-shelf device, or hack something together yourself. Commercial devices are polished and will look good in your home, but they send audio recordings from inside your home to the cloud. Yikes! DIY solutions can be designed with privacy in mind, keeping all processing and data local. However, they tend to take the form of a bare development board and a mess of wires — perhaps with a shoddy, 3D-printed case.

MiciMike was designed to give us the best of both worlds. It is a drop-in replacement PCB for the board found in first-generation Google Home Mini smart speakers. Swap in a MiciMike and you have a smart speaker that not only looks great, but that is also a fully local, privacy-respecting Home Assistant voice device.

Instead of relying on cloud services, the MiciMike board runs a local voice pipeline powered by an ESP32-S3 microcontroller and an XMOS XU316 voice processor. The design reuses much of the original hardware from the Google Home Mini — including the speaker, power daughterboard, touch sensors, and enclosure — while replacing the proprietary electronics with an open, community-driven platform.

This approach allows owners of older smart speakers to reclaim their devices from the cloud and integrate them into a local smart home ecosystem. Once installed, the modified device can interact directly with a Home Assistant setup to control lights, trigger automations, or manage media playback. Importantly, audio capture, wake-word detection, and preprocessing all happen locally on the device. Speech recognition and text-to-speech processing are handled by Home Assistant, which can run entirely on local hardware if the user prefers.

The hardware itself includes a two-microphone MEMS array designed for voice capture, along with four individually addressable RGB LEDs that provide feedback to the user. The board’s dimensions and mounting points match the original mainboard, allowing it to slot neatly into the first-generation Home Mini chassis without modification.

Firmware for the device is based on ESPHome and draws architectural inspiration from the Home Assistant Voice Preview Edition. However, the MiciMike hardware requires its own dedicated configuration to account for the different components used in the board.

Both the hardware and software are planned to be released as open source, with schematics, PCB layouts, and firmware configuration files made available to the community. The hardware will be published under the CERN-OHL-S v2 license, encouraging others to study, modify, and improve the design.

The price and release date have not yet been announced, but you can sign up for notifications over at Crowd Supply to stay in the know.