TrailText – an ESP32 and LoRa off-grid messaging app

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GitHub - brunokeymolen/lora: LoRa (Long Range) communication related projects · GitHub

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LoRa Experiments for Heltec WiFi LoRa 32

Two practical ESP32-S3 + SX1262 projects for testing LoRa links and sending text when normal networks are unavailable.

Projects

TrailText

Text when networks fail.

A BLE-to-LoRa messenger for Heltec WiFi LoRa 32 V4.3 boards.<br>A phone connects over BLE, the ESP32 encrypts the message with AES-256-GCM,<br>and the SX1262 radio carries it over LoRa to another device.

Firmware guide<br>Flutter app guide<br>Firmware source

LoRa<br>Ping-Pong

LoRa Ping-Pong

A simple range, antenna, and radio sanity test.

Flash the same firmware to two Heltec boards, press the user button,<br>and measure round-trip time, RSSI, and SNR. It is the fastest way to<br>prove the radio path before moving on to encrypted messaging.

Ping-Pong guide<br>Firmware source

LoRa Ping-Pong Hardware

TrailText Screenshots

What This Repo Gives You

Area<br>TrailText<br>LoRa Ping-Pong

Purpose<br>Encrypted off-grid text messaging<br>Link/range test between two boards

Hardware<br>Heltec WiFi LoRa 32 V4.3, ESP32-S3 + SX1262<br>Heltec WiFi LoRa 32 V4, ESP32-S3 + SX1262

Radio<br>LoRa 868 MHz EU defaults<br>LoRa 868 MHz EU defaults

Phone app<br>Flutter app over BLE<br>Not required

Security<br>AES-256-GCM over LoRa with shared PSK<br>Plain diagnostic packets

Display<br>OLED status and message feedback<br>OLED RTT/RSSI/SNR feedback

Color Palette

The visual identity follows the TrailText logo: deep night blue for the field,<br>cyan for the radio trail, and orange for location/signal accents.

Color<br>Use<br>Hex

Night background<br>#001B36

TrailText cyan<br>#00CFC8

Signal orange<br>#FF9F1C

Recommended Path

Start with LoRa Ping-Pong to confirm both boards, antennas, pins, frequency, and range.

Flash TrailText firmware once the radio link is known-good.

Build the TrailText Flutter app, connect over BLE, and send messages over LoRa.

Hardware Notes

Item<br>Notes

Boards<br>Heltec WiFi LoRa 32 V4 / V4.3

MCU<br>ESP32-S3

Radio<br>SX1262

Region defaults<br>868 MHz EU

Display<br>On-board OLED

Antenna<br>Attach before powering or transmitting

Always attach the antenna before powering a LoRa board. Transmitting without an antenna can damage the SX1262 radio front end.

Repository Layout

lora-ping-pong/ Range and radio link test firmware<br>lora-text/firmware/ TrailText ESP-IDF firmware<br>lora-text/app/ TrailText Flutter app source<br>lora-text/app/src/assets/images/<br>TrailText PNG logo assets<br>LICENSE.txt Creative Commons BY-NC-SA 4.0 notice

License

(C)2026 Bruno Keymolen bruno.keymolen@gmail.com

TrailText and the source in this repository are licensed under<br>Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International.

See LICENSE.txt and<br>creativecommons.org/licenses/by-nc-sa/4.0/.

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