MiciMike drop-in PCB replacement for Google Home Mini (Gen-1)

MiciMike Home Mini is a drop-in PCB replacement for the "Google Home Mini" (Google's first-generation smart speaker hardware with a Micro-USB charging port, but based on ESP32 and XMOS microcontrollers for running open-source firmware.

This is a fully open-source hardware project, taking some concep inspiration from the Onju Voice however aiming to follow Open Home Foundation's open voice assistants standard with Home Assistant Voice Preview Edition as reference for PCB designs and specifications.

Project scope

The goal of this project/repository and its sister-project is to design drop-in replacement PCBs (Printed Circuit Board) with hardware schematics following open voice assistants standard from the Open Home Foundation so that anyone can make or order from a one-stop PCB manufacturer as a custom drop-in replacement PCB for the Google Home Mini (1st Gen) to convert it into open-source voice assistant hardware.

These projects is primarly targeting people looking to repurpose their old Google Home Mini smart speakers into open-source hardware for Voice Control of Home Assistant and/or media player speaker output for Music Assistant, (the hardware can however probably also be used with other applications as well with other firmware as it is based on the popular Espressif ESP32 platform).

The hardware design will (similar to Home Assistant Voice Preview Edition) integrate an ESP32-S3 microcontroller for WiFi, BLE, and onboard wake-word detection (using the no-code ESPHome firmware firmware) + an XMOS xCORE XU316 chip for advanced audio processing (with custom firmware for microphone cleanup offloading for better voice recognition capabilities by using using locally running algorithms for Noise Suppression, Acoustic Echo Cancellation, Interference Cancellation, and Automatic Gain Control).

Again, functionality-wise it is made to be mostly hardware comatible with the Home Assistant Voice Preview Edition (a.k.a. Home Assistant Voice PE reference design (which has been released as open-source hardware design from Open Home Foundation in coolaboration with Nabu Casa). The main difference will be due to very tight constraints defined by the Google Home Mini enclosures and its other comonents, (the design of the replacement PCBs will therefore be limited by the same type of physical capacity inputs as the original hardware from Google).

As such the scope for these projects is not to develop new features/functions for the ESPHome and XMOS firmware, so if you want that then you instead need to turn to the firmware development of the Home Assistant Voice Preview Edition as well as to the upstream ESPHome repositories on GitHub:

- https://github.com/esphome/home-assistant-voice-pe

- https://github.com/esphome/esphome

- https://github.com/esphome/voice-kit-xmos-firmware

Request for collaboration and contributions

If you like to show your support me working on this project please consider buying me a coffee via Ko-fi ☕ 

For reference, you can find some more background information about the original concept/idea see and post to Home Assistant related community discussion in this Home Assistant community forum thread:

- https://community.home-assistant.io/t/any-news-on-alternative-to-onju-voice-pcb-repacement-design-for-google-nest-home-mini-speakers-with-added-xmos-chip-to-match-official-home-assistant-voice-preview-edition-reference-hardware/860001/

Tools used

- 🛠️ KiCad 9

- 🧰 SnapEDA / LCSC for footprint sourcing

Hardware specifications

- 4-layer PCB

- ESP32-S3R8 bare chip (ESP32-S3 for WiFi, BLE, and onboard wake-word detection) with 16MB flash

- XMOS XU316-1024-QF60B-C24 (XMOS XU316 xCORE DSP audio processing) with 4MB flash

- Dual I²S buses (to allow I2S interfaces at the same time, i.e. simultaneous audio output and audio input)

- AIC3204 DAC and TPA6211 PA for speaker output

- 2x MEMS microphones (dual T3902 with 68mm inter-mic spacing)

- 4x SK6812 RGB LEDs

References

Home Assistant Voice Preview Edition resources including PCB design files

- https://www.home-assistant.io/blog/2024/12/19/voice-preview-edition-the-era-of-open-voice/

- https://voice-pe.home-assistant.io/resources/

- https://support.nabucasa.com/hc/en-us/categories/24451727188125-Home-Assistant-Voice-Preview-Edition

- https://support.nabucasa.com/hc/en-us/sections/24980381645213-Resources

ESPHome firmware for Home Assistant Voice PE (which also use the same ESP32-S3 + XMOS XU316 combination):

- https://github.com/esphome/home-assistant-voice-pe

- https://esphome.github.io/home-assistant-voice-pe/

- https://voice-pe.home-assistant.io/

XMOS xCORE DSP (XU316-1024-QF60B-C32) MCU IC chip

- https://www.xmos.com/download/XU316-1024-QF60B-xcore.ai-Datasheet(3).pdf

- https://www.xmos.com/software-tools/

- https://www.xmos.com/develop/xcore-voice

- https://www.xmos.com/usb-multichannel-audio/

- https://www.xmos.com/xcore-ai

XMOS firmware from the ESPHome prokect for the Home Assistant Voice Preview Edition hardware:

- https://github.com/esphome/voice-kit-xmos-firmware

- https://github.com/esphome/xmos_fwk_rtos

- https://github.com/esphome/xmos_fwk_io

License

This project is licensed under the [CERN Open Hardware License Version 2 - Strongly Reciprocal (CERN-OHL-S v2)]

Any modified version of this hardware must also be distributed under the same license.

Disclaimer

This is a hobby project provided as is, without any guarantees. I do not take responsibility for any design errors, manufacturing issues, assembly problems, misuse, or user-induced damage. By using these files or ordering this PCB, you acknowledge that failures or malfunctions cannot be ruled out, and you do so entirely at your own risk.

Important Note

The included XMOS firmware must be requested to be flashed during the PCB order process. If the firmware is not written to the flash by the manufacturer, the hardware will not function as intended and will be unusable, unless you flash it yourself at home. This second option requires an external flash writer device.

The ESPHome configuration is heavily based on the Home Assistant Voice Preview Edition code, with some hardware-specific modifications. The code is far from perfect, but it works.

The touch configuration may need some fine-tuning, as every piece of hardware behaves slightly differently, even with the same specifications. The values you see here are what work with my enclosure and PCB. Unfortunately I haven’t found a way to do automatic calibration under ESP-IDF like we had with the Arduino framework.

An extra component is required for anyone who wants to install this PCB: a 50mm straight type A 0.5mm pitch 16 pole FPC cable. I chose this solution instead of desoldering the original FPC cable from the old board and soldering it onto the new one (the FPC soldering process is not easy). Therefore, I decided to replace the old cable with one that can be connected to FPC connectors on both sides.