T-Beam LoRa “Hello” Link (Sender + Receiver) — RadioLib (SX1262, 868 MHz)

A minimal two-device project using two LILYGO T-Beam V1.2 (ESP32 + SX1262) boards to communicate over LoRa in the EU 868 MHz band.

One T-Beam acts as a Sender and periodically transmits a short text message ("hello").
The other T-Beam acts as a Receiver and continuously listens, printing received messages plus signal quality information (RSSI/SNR) to the serial monitor.

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What is LoRa (in plain words)?

LoRa is a long-range, low-power radio technology.
Think of it like “walkie-talkies for tiny data”:

• ✅ Works over long distances (often hundreds of meters to kilometers depending on environment)
• ✅ Uses very little power
• ✅ Sends small messages (not suitable for high-speed data like Wi‑Fi)

In this project, LoRa is used to send a simple text message from one board to another.

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Software Overview

This repository contains two independent firmware programs:

• main_send.cpp — runs on the Sender T-Beam
  Sends "hello" every 2 seconds.

• main_receive.cpp — runs on the Receiver T-Beam
  Listens for incoming messages and prints them to Serial.

Both programs use the RadioLib library to control the SX1262 LoRa radio on the T-Beam.

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Program Logic (How it works)

1) Sender (main_send.cpp)

1. Starts the serial port (so you can see logs on your PC).
2. Initializes the SX1262 radio at 868.0 MHz.
3. Every 2 seconds:
   • Transmits the text message "hello".
   • Prints whether the transmission succeeded.

Key idea: the sender does not “connect” like Bluetooth/Wi‑Fi. It simply broadcasts a LoRa packet.

2) Receiver (main_receive.cpp)

1. Starts the serial port.
2. Initializes the SX1262 radio at 868.0 MHz (must match the sender).
3. Continuously calls radio.receive(...):
   • If a message arrives, it prints:
     • the received text
     • RSSI (signal strength)
     • SNR (signal quality)

Key idea: the receiver is always listening. When a packet arrives, it reads it and reports signal metrics.

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Features

• ✅ Simple “Hello World” LoRa link (Sender → Receiver)
• ✅ Uses EU 868 MHz frequency
• ✅ Serial logging for easy debugging
• ✅ Receiver prints RSSI and SNR
• ✅ Built with PlatformIO + Arduino framework
• ✅ Uses RadioLib (SX1262 support)

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Hardware / Components Used

Boards

• 2× LILYGO T-Beam V1.2
  • MCU: ESP32
  • LoRa radio: SX1262
  • GPS: NEO-M8N
  • PMU: AXP2101
  • USB-UART: CH9102
  • Flash: 4MB, PSRAM: 8MB
  • Marking: LILYGO 868/915 MHz Model: LORA32 SX1262

Region / Frequency

• Europe (EU): 868 MHz is used in the code:
  • static const float LORA_FREQ = 868.0;

⚠️ Always follow your local radio regulations (frequency, transmit power, duty cycle).

Dependencies / Libraries Used

• Arduino framework (ESP32)

• RadioLib by Jan Gromeš

  Used to control the SX1262 LoRa radio. In PlatformIO, you typically add:

  lib_deps = jgromes/RadioLib Build & Flash (PlatformIO)

Prerequisites

• Install VS Code

• ✅ Install the PlatformIO extension

• Connect your T-Beam via USB (CH9102 driver may be required depending on your OS)

• Compile & Upload

• Platform IO requires, that the main program is named main.cpp, and any other file with the suffix .cpp will be used when compiling code. Therefore, when compiling and uploading the program for sender, (Sender T-Beam connected with USB cable to computer) the file main_sender.cpp must be renamed to main.cpp, and the file main_receive.cpp must be renamed to main_receive.xxx. Then, after the sender program has been compiled and uploaded, vice versa, the main_sender.cpp must be renamed to main_sender.xxx and the main_receive.cpp must be renamed to main.cpp. And then connect the receiver device to the computer and compile and upload the receiver program.

• Open the sender project and run:

• Build

• Upload

• Monitor (Serial Monitor at 115200 baud) -Repeat for the receiver project.

-Serial Monitor Settings -Baud rate: 115200

Sender output example:

-SX126x Sender starting...

• Radio init OK

• Sending: hello

• TX success

• Receiver output example:

• SX126x Receiver starting...

• Radio init OK

• Listening...

• RX: hello

• RSSI: -xx dBm, SNR: x.x dB

Usage

• Flash Receiver firmware to one T-Beam.

• Flash Sender firmware to the other T-Beam.

• Power both devices (USB or battery).

• Open serial monitors:

• Receiver should print "hello" whenever it receives a packet.

• Sender should report successful transmissions.

• If you see TX success but no RX:

• Ensure both use the same frequency (868.0)

• Ensure LoRa parameters match (SF/BW/CR if you set them)

• Verify antenna is connected

• Verify correct SX1262 pin mapping (RST/BUSY/DIO1/NSS)

Future Improvements

• Add a real ACK (acknowledgement) message:
• Receiver sends back “ACK”
• Sender waits for ACK and retries if not received
• Add message counters and timestamps
• Add configurable LoRa parameters (SF/BW/CR) via #define or Serial commands
• Add encryption/authentication (basic integrity protection)
• Add deep sleep for low-power battery operation
• Add structured payloads (JSON or binary packets)

Acknowledgements

• RadioLib library by Jan Gromeš and contributors
• LILYGO for the T-Beam hardware platform

License

• This project is licensed under the MIT License. See the LICENSE file for details.

Images

2. 3.