WS2812B-2020 8x8

Devais - Handheld AI Assistant Device

A battery-powered, pocket-sized AI assistant with a push-to-talk interface. Designed as a walkie-talkie style device that solves the common problem of AI apps responding to hesitation during speech.

Overview

Form Factor: Stick-shaped handheld device (~30x30x150mm)
Power: 18650 battery with USB-C charging
Interface: Push-to-talk button, status LEDs, speaker and microphone
Connectivity: Bluetooth Low Energy (nRF52840)

Hardware Components

Core Controller

• Seeed XIAO nRF52840 - Ultra-low power microcontroller with BLE
  • Superior battery efficiency vs ESP32 alternatives
  • 20.8 days idle battery life (vs 8.3 days for ESP32-C3)
  • 5 days continuous audio streaming (vs 27 hours for ESP32-C3)

Audio System (I2S Bus Architecture)

• INMP441 - MEMS I2S microphone
• MAX98357A - I2S Class D amplifier
• Compact speaker
• Shared clock signals with separate data lines for efficiency

User Interface

• Tactile push-to-talk button
• Power/mode button
• Status LEDs (power, connectivity, activity)

Power

• 18650 Li-ion battery
• USB-C charging port
• Efficient power management optimized for audio streaming

Project Structure

devais/
├── cad/              # 3D CAD models (CadQuery scripts)
├── firmware/         # nRF52840 firmware
├── docs/             # Documentation, wiring diagrams
├── hardware/         # PCB designs, schematics
└── README.md

Getting Started

Prerequisites

• Python 3.14
• uv (Python package manager)
• Prusa MK3S or compatible 3D printer

Installation

# Clone the repository
git clone https://github.com/stigsb/devais.git
cd devais

# Install dependencies with uv
uv sync

# Activate virtual environment
source .venv/bin/activate  # Linux/Mac
# or
.venv\Scripts\activate     # Windows

Running CAD Scripts

# Generate the enclosure model
python cad/enclosure.py

# Output will be in cad/output/ as STL files

Design Principles

1. Intentional Interaction - Push-to-talk prevents accidental triggers and hesitation issues
2. Battery Efficiency - Component selection optimized for multi-day battery life
3. Pocket Portability - Narrow form factor fits comfortably in pocket or hand
4. Programmatic CAD - Python-based modeling enables iterative design and parameter adjustment

Status

• Component selection and power analysis
• I2S audio architecture design
• Wiring diagram and pin assignments
• 3D enclosure design (in progress)
• PCB layout
• Firmware development
• Prototype assembly

Location

Trondheim, Norway

License

TBD