Introduction

I’ve always been fascinated by the fact that we can transmit data for a long distance between two devices.

The thing that is fantastic is that it can be done totally free or charge without the use of a mobile subscription.

These two devices allow to send and receive small messages using LoRa technology:

• #ESP32

• #RFM95

• #Battery

• #Antenna

• #PCBWay

#pcbway #arduino #arduinoproject #esp32 #rfm95 #lora

Video

How to change config

- In case you need to add other devices, you need to modify the "localAddress" variable and make it unique

- In case you need to address a specific device, you need to modify the "destination" variable and put the value of the device you want to message

- In case you want to message all devices, you need to put the value 255 in the "destination" variable.

- In case you want to add more messages, you need to modify the "messages.h" file and change the NUMBER_OF_STRING with a value equal to the number of messages you want to have as options. Then you need to add the string at the end of the "char arr" array.

EXPANDED TECHNICAL DETAILS

Long-Range Decentralized Messaging

This project builds a handheld text communicator capable of sending messages over several kilometers without a cellular or internet connection.

• Semtech LoRa Modulation: Uses the SX1276/SX1278 (RFM95) LoRa module. The Arduino manages the 433MHz or 915MHz spread-spectrum radio link, providing reliable communication even through dense urban environments.
• OLED UI Keyboard Matrix: Interfaces with a small matrix keyboard and a 128x64 OLED screen. The firmware handles character input, message buffering, and displaying CRC-verified incoming messages.

Reliability

• Automatic Retransmission (ARQ): Includes an acknowledgement logic; if the receiving unit doesn't acknowledge a message within 2 seconds, the Arduino automatically retransmits the packet at a higher power level.