microReticulumTbeam/exercises/01_lora_ascii_pingpong

Exercise: LoRa Transmission Validation (SX1262)

Overview

This exercise validates raw LoRa packet transmission from the LILYGO T-Beam SUPREME V3.0 using the onboard SX1262 radio.

The objective is to:

1. Transmit deterministic LoRa packets at known parameters.

2. Confirm successful reception using:

   • A second T-Beam
   • A Waveshare SX1303 concentrator sniffer
   • Or any SDR/LoRa receiver configured with identical PHY settings

3. Verify correct alignment of frequency, spreading factor, bandwidth, and coding rate.

This is a PHY-layer validation exercise, not LoRaWAN.

---

Hardware

Transmitter

• Board: LILYGO T-Beam SUPREME V3.0
• MCU: ESP32-S3
• Radio: SX1262
• Antenna: 915 MHz tuned antenna
• Power: USB-C or 18650 battery

Receiver / Sniffer

Any device capable of raw LoRa reception with manual PHY configuration:

• Second T-Beam (SX1262)
• Waveshare SX1303 + lora_pkt_fwd
• SDR with LoRa demodulator

---

LoRa Radio Specifications

The sniffer must match these parameters exactly.

Parameter	Value
Radio Chip	SX1262
Frequency	915.000 MHz
Modulation	LoRa
Bandwidth	125 kHz
Spreading Factor	SF8
Coding Rate	4/5
Preamble Length	8 symbols
Sync Word	0x12 (Public LoRa)
CRC	Enabled
IQ Inversion	Disabled
Output Power	14 dBm (default)

---

Important Notes for Sniffer Operators

1. Frequency

Ensure your sniffer JSON or configuration file contains:

"freq": 915000000

If using SX130x HAL:

915000000

No offset. No channel hopping.

---

2. Spreading Factor

Must be:

SF8

If the sniffer is set to multi-SF mode, confirm that SF8 is enabled.

---

3. Bandwidth

125000 Hz

Not 250 kHz. Not 500 kHz.

---

4. Coding Rate

4/5

Some interfaces represent this as:

CR = 1

---

5. Sync Word

If your sniffer filters on sync word:

0x12

This is the public LoRa sync word (not LoRaWAN private).

---

Expected Packet Behavior

The transmitter:

• Sends a short ASCII payload
• Repeats at a fixed interval
• Does not use LoRaWAN
• Does not use encryption
• Does not use MAC layer framing

Sniffer output should display:

• RSSI
• SNR
• SF8
• BW125
• Payload length matching transmitter

---

Confirming Correct Alignment

A properly aligned sniffer will show:

• Stable RSSI
• Correct SF detection (SF8)
• Clean CRC pass
• No excessive packet loss at short range

If you see:

• No packets → Check frequency mismatch first.
• Packets but CRC fail → Check bandwidth mismatch.
• Packets only intermittently → Check spreading factor.

---

SX1262 SPI Mapping (T-Beam SUPREME)

For reference, the radio is connected as follows:

Signal	ESP32-S3 Pin
SCK	12
MISO	13
MOSI	11
CS	10
RESET	5
BUSY	4
DIO1	1

These match the board’s hardware routing.

---

Build & Flash

PlatformIO

1. Open project folder
2. Select correct environment
3. Compile
4. Upload via USB-C
5. Monitor serial output

Arduino IDE

• Board: ESP32S3 Dev Module
• Flash: 8MB
• PSRAM: QSPI
• Upload speed: 921600
• USB Mode: CDC and JTAG

---

Purpose of This Exercise

This exercise verifies:

• SPI communication with SX1262
• Radio configuration correctness
• Antenna functionality
• Sniffer alignment
• Baseline RF performance

It is intended as the foundational RF validation step before:

• Reticulum interface integration
• microReticulum radio abstraction
• LoRa time-synchronized experiments
• Multi-node field testing

---

If You Cannot See Packets

Work through this checklist:

1. Confirm antenna attached.
2. Confirm sniffer at 915 MHz.
3. Confirm SF8.
4. Confirm BW125.
5. Reduce distance to < 2 meters.
6. Increase TX power to 17–20 dBm for testing.
7. Confirm no regional regulatory lock mismatch.

---

Relationship to main.cpp

This README corresponds to the current exercise implementation in:

main.cpp

See source for definitive parameter values

If you modify radio parameters in code, update this README accordingly.