Meshtastic Build on ESP32-S3: LoRa E22

Building a Meshtastic Node with ESP32-S3 and LoRa E22-900M30S: A Step-by-Step Guide

To build a Meshtastic node using an ESP32-S3 Super Mini, you'll need the following components:

• ESP32-S3 Super Mini
• LoRa module E22-900M30S
• GPS Neo-6M v2
• 0.96" OLED display (SSD1306, 128x64)
• 868 MHz LoRa antenna (5 dBi, SMA)
• USB-UART converter
• Jumper wires and breadboards

The total cost, excluding consumables, is around $20. This setup allows for a deeper understanding of the hardware and the flexibility of the ESP32-S3's GPIO matrix.

Wiring Diagram

The ESP32-S3 offers advanced remapping capabilities for SPI, I2C, and UART interfaces. Avoid using system pins (USB, boot). Example pinout for the LoRa E22-900M30S:

• SX126X_CS (NSS): GPIO 10
• LORA_SCK: GPIO 11
• LORA_MOSI: GPIO 12
• LORA_MISO: GPIO 7
• SX126X_RESET: GPIO 6
• SX126X_BUSY: GPIO 5
• SX126X_DIO1: GPIO 4

For the OLED (I2C):

• I2C_SCL: GPIO 9
• I2C_SDA: GPIO 8

The GPS Neo-6M connects only via TX (GPIO 1) to avoid conflicts with the debug UART.

Adapting the Meshtastic Firmware

Clone the firmware repository:

git clone https://github.com/meshtastic/firmware

Install PlatformIO (on macOS: brew install platformio). Navigate to variants/esp32s3/EBYTE_ESP32-S3.

Edit variant.h:

#define SX126X_CS 10   // EBYTE module's NSS pin
#define LORA_SCK 11
#define LORA_MOSI 12
#define LORA_MISO 7
#define SX126X_RESET 6
#define SX126X_BUSY 5
#define SX126X_DIO1 4

// I2C
#define I2C_SCL 9
#define I2C_SDA 8

#define HAS_SCREEN 1

#define GPS_TX_PIN 1

In platformio.ini, specify the speeds:

upload_speed = 115200
monitor_speed = 115200

Build: pio run -e EBYTE_ESP32-S3.

Flashing via External USB-UART

The built-in USB on budget ESP32-S3 Super Mini boards can be unstable. Connect the adapter:

• 5V → 5V
• GND → GND
• TX adapter → RX board
• RX adapter → TX board

Upload: pio run -e EBYTE_ESP32-S3 -t upload. For boot mode:

• Hold Boot
• Press Reset
• Release Reset
• Release Boot after 1 second

Optimization and Testing

After flashing, the node will recognize the LoRa E22-900M30S, OLED, and GPS. Test the mesh network on 868 MHz. Next, solder onto a PCB to eliminate loose wires.

Key Points:

• The flexible GPIO matrix of the ESP32-S3 simplifies custom builds.
• Base your setup on the EBYTE_ESP32-S3 variant for the E22-900M30S.
• Connect GPS only via TX to preserve the UART for debugging.
• An external USB-UART stabilizes flashing on inexpensive boards.

— Editorial Team