Offline Mesh-Based Wireless Communication System Using ESP32 and OLED Display with ESP-NOW Protocol

Abstract

Conventional communication systems depend on internet infrastructure and cellular networks, which may become unavailable during disasters, in remote areas, or in military field operations. This paper presents the design and implementation of an Offline Mesh-Based Wireless Communication System using two ESP32 microcontrollers, a 4×4 matrix keypad for input, and a 0.91-inch OLED display (SSD1306) for real-time message rendering. The system leverages ESP-NOW, a lightweight, connectionless peer-to-peer protocol developed by Espressif Systems, enabling direct MAC-address-based data transfer without requiring a Wi-Fi router or internet access. Each node is configured as both transmitter and receiver, facilitating bidirectional communication. The prototype achieved message delivery latency below one second, a stable open-space range of approximately 60 metres, and continuous operation exceeding three hours on a 10,000 mAh power bank. The system is low-cost, portable, and can be extended to a multi-node mesh topology, demonstrating practical utility for disaster management, rural connectivity, defence communication, and IoT-based offline control systems. Each ESP32 node is configured to operate as both atransmitter and receiver, allowing bidirectional text communication between users. The system incorporates a Nokia-style multi-tap text input mechanism through the matrix keypad and displays transmitted and received messages on the OLED display. Experimental evaluation was conducted under open-air, indoor line-of-sight, andwall-obstructed environments to analyze communication performance. The prototype achieved message delivery latency below one second, communication ranges of up to 60 metres in open environments, reliable message delivery exceeding 99%, and continuous operation for more than three hours using a 10,000 mAh portable power source.

Introduction

The paper presents an Offline Mesh Chat System (OMCS), a low-cost communication solution that enables text messaging without relying on internet connectivity, mobile towers, or Wi-Fi routers. The system is designed for use in disaster situations, remote locations, and military environments where conventional communication infrastructure may be unavailable. It uses ESP32 microcontrollers, ESP-NOW wireless communication, a 4×4 matrix keypad for Nokia-style multi-tap text entry, and a 0.91-inch OLED display for message viewing. The decentralized mesh-networking approach allows devices to communicate directly without external infrastructure.

The literature review compares existing offline communication technologies, including Bluetooth Mesh, LoRa, and Wi-Fi-based microcontroller systems. Bluetooth offers limited range, while LoRa provides long-distance communication but with low bandwidth. Previous ESP32-based projects often required routers, whereas the proposed OMCS uses ESP-NOW for direct, low-latency, router-free communication. The novelty of the system lies in combining bidirectional ESP-NOW messaging with keypad input and persistent message display in a single standalone prototype.

The hardware architecture consists of an ESP32 DevKit V1, a 4×4 membrane keypad, an SSD1306 OLED display, and a regulated power source. The ESP32 handles both communication and user-interface tasks, while the keypad uses row-column scanning and multi-tap character input. Messages are displayed on the OLED screen via I²C communication. The system currently has limitations such as limited display space, lack of encryption, no message storage, and reduced durability due to breadboard-based construction.

Communication is achieved using ESP-NOW, a lightweight Wi-Fi-based protocol that operates without network association. It supports payloads up to 250 bytes, low latency, and direct communication between registered peer devices. Messages are packaged in a structure containing the sender’s MAC address and text content, allowing receivers to identify message origins. The software manages message composition, transmission, reception, and display updates through dedicated callbacks and control keys.

Performance testing showed strong results, including sub-second message latency, 99% delivery success within 60 meters, open-air communication up to 60 meters, indoor range of 40 meters, and through-wall communication up to 30 meters. Battery testing demonstrated more than 3 hours of operation using a 10 Ah power source. Compared with Bluetooth, LoRa, and Zigbee, ESP-NOW provides a favorable balance of range, speed, cost, and offline capability for real-time text communication.

Future enhancements include developing a true multi-node mesh network with routing capabilities, adding AES-128 encryption for security, implementing message history storage, upgrading to larger displays, incorporating solar-powered battery systems, and integrating LoRa modules to extend communication over much longer distances. Overall, the OMCS demonstrates an effective, affordable, and infrastructure-free communication platform suitable for emergency and remote-area applications.

Conclusion

This paper presented the design, implementation, and empirical evaluation of an Offline Mesh-Based Wireless Chat System built on ESP32 microcontrollers communicating via the ESP-NOW protocol. The system demonstrated sub-second message latency, a usable range of 60 m in open space and 30 m through a masonry wall, message delivery reliability above 99%, and battery autonomy exceeding three hours—all without any internet infrastructure. The Nokia-style multi-tap keypad combined with a persistent OLED display provides an accessible human interface. The prototype offers practical value for disaster relief, military communication, rural connectivity, and education, while serving as a springboard for more capable decentralized mesh networks.

References

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Copyright

Copyright © 2026 Atharv Dnyaneshwar Margale, Pranav Shankar Mankar, Basweshwar Gangadhar Waghmare. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.