TrailLink - Communication Device
A lightweight, battery-efficient peer-to-peer (P2P) communication system designed to keep hiking groups connected—even in remote areas with no Wi-Fi or cellular service. Check out our final video! (Shout out to Alex Apollonov!)
Overview
TrailLink is a simple and reliable messaging device that uses the ESP-NOW protocol to enable short, predefined message exchanges between hikers. Whether you’re hiking, camping, or in areas with limited connectivity, TrailLink ensures your group stays in touch.
🛠 Built with ESP32 S3
📶 Communicates using ESP-NOW (no internet required)
📬 Supports predefined messages for efficient interaction
🔋 Battery-efficient and portable
📦 3D-printed enclosure for durability in the field
Problem
When hiking in groups across remote terrains, physical distance can lead to disconnection and safety concerns. Cellular and Wi-Fi networks often fail in such environments, making a dedicated offline communication system essential.
Key Features
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Battery Efficient: Runs on a 9V battery with power regulation
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P2P Mesh Networking: Uses ESP-NOW for direct or relayed communication
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Simple UI: OLED screen for reading messages and button-based input
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Inbox System: View received messages
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Message Relay: Messages can hop across intermediate devices
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Transmission Range: ~150m verified range
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Scalable: Supports 4+ users per group and up to 35 messages per package
System Architecture
📦 Hardware
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ESP32 S3 Dev Module
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OLED Display (I2C interface)
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Push Buttons for input
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9V Battery + Voltage Regulator
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Custom PCB (Designed in KiCad)
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3D Printed Enclosure with access for USB-C charging, buttons, and battery
🧠 Software
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ESP-NOW Protocol for low-power, low-latency communication
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Message State Machine for managing send/receive/relay
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Predefined Message System for quick, structured communication
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Inbox and Bulletin Board System: Savepoint-based messaging
Device Block Diagram
Message Relay Mechanism
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Messenger Mode: Users carry and forward messages physically across nodes.
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Bulletin Board Mode: Devices left at fixed locations act as message savepoints.
State Diagram
The device follows a structured flow:
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Start State
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Action Decision (Send, Receive, or Pair)
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Based on input:
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Send → Carry/Broadcast Message
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Receive → Display or Store Message
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Results
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✅ Tested Transmission Range: 150 meters
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✅ Support for Groups: 4+ users
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✅ Scalability: Up to 35 messages per transmission
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✅ Reliable P2P Communication without needing Wi-Fi or mobile data
Authors
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Keng-Lien Lin
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Roberto Reyes
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Hou Dren Yuen
Developed as part of ECE 196 (Spring 2025) at UC San Diego - Department of Electrical and Computer Engineering