🏗️ Reachy Mini Architecture Deep Dive
📊 System Architecture
┌──────────────────────────────────────────────────────────┐
│ REACHY MINI ROBOT │
├──────────────────────────────────────────────────────────┤
│ │
│ ┌─────────────────────────────────────────────────┐ │
│ │ RASPBERRY PI 4 (Main Computer) │ │
│ ├─────────────────────────────────────────────────┤ │
│ │ │ │
│ │ Web Dashboard (Port 8000) │ │
│ │ ├── Uvicorn ASGI Server │ │
│ │ ├── FastAPI Application │ │
│ │ └── Static HTML/JS Interface │ │
│ │ │ │
│ │ Backend Services │ │
│ │ ├── reachy-sdk-server (NOT auto-started) │ │
│ │ ├── Motor Control Service │ │
│ │ └── Camera Service (optional) │ │
│ │ │ │
│ │ Communication Buses │ │
│ │ ├── I2C Bus → Motor Controllers │ │
│ │ ├── USB → Cameras (if connected) │ │
│ │ └── GPIO → Status LEDs │ │
│ └─────────────────────────────────────────────────┘ │
│ │ │
│ │ I2C/Serial │
│ ↓ │
│ ┌─────────────────────────────────────────────────┐ │
│ │ DYNAMIXEL MOTOR CONTROLLERS │ │
│ ├─────────────────────────────────────────────────┤ │
│ │ • XL330-M077 Smart Servos (7x) │ │
│ │ • Daisy-chained communication │ │
│ │ • Position/Speed/Torque control │ │
│ │ • 1 Mbps serial communication │ │
│ └─────────────────────────────────────────────────┘ │
└──────────────────────────────────────────────────────────┘
🔌 Communication Interfaces
1. Web Server (Port 8000)
- • Protocol: HTTP/REST API
- • Access: http://reachy-mini.local:8000
- • Pre-recorded movements only
- • Dashboard interface
- • Limited real-time control
2. gRPC SDK (Port 50055)
- • Protocol: gRPC
- • Direct motor control
- • Real-time feedback
- • Camera access
- • Custom movements
3. SSH Access (Port 22)
- • Full system control
- • Install custom software
- • Direct hardware access
- • User: pollen
- • Password: root
4. Direct Serial
- • Dynamixel Protocol 2.0
- • 1 Mbps TTL Serial
- • Raw motor packets
- • /dev/ttyUSB0
- • Complete control
🔄 Control Flow
Web Interface Flow:
Browser → HTTP → Web Server → Backend Check → Pre-recorded Move → Motors
SDK Control Flow:
Python → gRPC → SDK Server → Direct Commands → Dynamixel → Motors
Direct Hardware Flow:
Your Code → Serial Port → Dynamixel Protocol → Motor Response
⚙️ Hardware Components
🧠 Computing
- • Raspberry Pi 4
- • 4GB RAM
- • 32GB SD Card
- • Raspbian OS
- • WiFi/Ethernet
🦾 Motors
- • 7x Dynamixel XL330
- • Smart servos
- • Position feedback
- • Temperature monitoring
- • Daisy-chained
📹 Sensors
- • 2x USB Cameras
- • Stereo vision
- • V4L2 interface
- • Microphone (USB)
- • Speaker (3.5mm)
💡 Key Architectural Insights
1. Two-Stage Boot: Web server starts automatically, but motor control backend requires manual activation for safety.
2. Timeout Issue: The backend service (not web server) times out after inactivity. Our keep-alive sends periodic requests to prevent this.
3. Limited Web API: HTTP interface only plays pre-recorded movements. Real robotics requires SDK or direct control.
4. gRPC is Native: The web API is a simplified wrapper. gRPC protocol provides full access to all robot capabilities.
5. Everything is Linux: Full SSH access means you can install anything - custom servers, AI models, computer vision, etc.
🚀 Your Control Options
Current: Using web API with keep-alive for basic demos ✅
Next Level: Install reachy-sdk for direct Python control 🎯
Advanced: SSH in and deploy custom FastAPI server 🚀
Ultimate: Direct Dynamixel protocol for microsecond control 💪