# Building a Custom Meshtastic Node with ESP32 + SX1262 (DIY Guide) I want this guide to constantly evolve. If you want to suggest changes I could make I have uploaded the markdown file from which this blog post is being generated here: For changes you want to suggest, email me here: [merlin@merlin-glander.de](mailto:merlin@merlin-glander.de) This guide documents how to build a **fully custom Meshtastic node** using a generic **ESP32 DevKit** and an **SX1262 LoRa module**, powered from a **single 18650 battery** with proper charging, protection, and voltage regulation. The focus of this guide is **doing it the correct way**: * No runtime pin hacks * No trial-and-error wiring * No prebuilt Meshtastic boards * Fully reproducible and explainable If you are comfortable with soldering and the terminal, this guide is for you. --- ## Why Build a Custom Node? Building your own Meshtastic node gives you: * Full control over hardware and power design * Better understanding of how Meshtastic actually works * Flexibility to reuse parts you already have * No vendor lock-in * Easier debugging and modification later This setup is electrically equivalent to many commercial nodes — just without the markup. --- ## Important Concepts (Read This First) ### Radio pins are compile-time only Meshtastic **does not allow changing LoRa radio pins at runtime** via the CLI or the mobile app. All radio pin assignments: * Are defined in firmware * Must be compiled in * Require a rebuild if you change wiring If you try to set radio pins using the CLI, it will **not work**. --- ### SX1262 is not “just SPI” Unlike older SX127x radios, the SX1262 **requires additional control signals**: * `BUSY` — mandatory * `DIO1` — mandatory (interrupt/IRQ) * `NRST` — strongly recommended If any of these are missing or miswired, the radio will fail with: ``` SX126x init result -2 ``` This error almost always means **wiring**, not software. --- ## Hardware Used ### Core electronics * ESP32 DevKit (ESP32-WROOM-32, e.g. `esp32doit-devkit-v1`) * SX1262 LoRa module (RA-62 / HT-RA62 / LLCC68-compatible) * 18650 Li-ion battery ### Power system * TP4056 **with battery protection** * MT3608 DC-DC boost converter ### Misc * USB cable (flashing/debugging) * Jumper wires or soldered connections * Antenna appropriate for your region (EU868 / US915, etc.) ⚠️ **SX1262 is 3.3 V only. Never connect it to 5 V.** --- ## Power System Design (Battery + Charging) This build uses a **safe and robust battery system** suitable for unattended operation. ### Components and roles #### TP4056 (with protection) * Charges a single 18650 cell via USB * Includes: * Over-charge protection * Over-discharge protection * Short-circuit protection * Battery connects to `B+ / B-` * Load is taken from `OUT+ / OUT-` #### MT3608 boost converter * Boosts battery voltage (≈3.0–4.2 V) * Output is adjusted to **5.0 V** * Feeds the ESP32 via its **VIN / VN** pin --- ### Power wiring overview ``` 18650 Battery │ ▼ TP4056 (with protection) ├─ B+ / B- → Battery └─ OUT+ / OUT- → MT3608 input │ ▼ MT3608 (set to 5.0 V) │ ▼ ESP32 VIN / VN ``` ### Why this works well * ESP32 receives stable voltage even as battery discharges * Battery is protected from damage * Charging and load paths are properly isolated * SX1262 is powered from ESP32’s onboard 3.3 V regulator --- ## SX1262 ↔ ESP32 Pin Assignment This is the **exact pin mapping used in the working firmware**. | SX1262 Pin | ESP32 GPIO | Purpose | | ---------- | ---------- | ------------------------ | | VCC | 3V3 | Radio power | | GND | GND | Common ground | | NSS (CS) | GPIO5 | SPI chip select | | SCK | GPIO18 | SPI clock | | MOSI | GPIO23 | SPI data (ESP32 → radio) | | MISO | GPIO19 | SPI data (radio → ESP32) | | NRST | GPIO14 | Radio reset | | DIO1 | GPIO26 | Radio interrupt (IRQ) | | BUSY | GPIO25 | Radio busy indicator | | DIO2 | — | Not used | | DIO3 | — | Not used | | TXEN | — | Not used | | RXEN | — | Not used | --- ## Wiring Checklist Before powering on: * MT3608 output verified at **5.0 V** * ESP32 powered via **VIN / VN** * SX1262 powered from **3V3** * NSS → GPIO5 * BUSY → GPIO25 * DIO1 → GPIO26 * NRST → GPIO14 * All grounds connected * Antenna attached Most SX1262 problems are wiring mistakes — triple-check this. --- ## Getting the Meshtastic Firmware Meshtastic uses **PlatformIO**, not the Arduino IDE. ```bash git clone https://github.com/meshtastic/firmware.git cd firmware git checkout develop ``` --- ## Creating a Custom Variant Meshtastic organizes board definitions as **variants**. Create a new variant directory: ```bash cd variants mkdir esp32_devkit_sx1262 ``` Directory structure: ``` variants/esp32_devkit_sx1262/ ├── platformio.ini └── variant.h ``` --- ## `platformio.ini` (Exact Working Configuration) ```ini [env:esp32_devkit_sx1262] extends = esp32_base board = esp32doit-devkit-v1 build_flags = ${esp32_base.build_flags} -D PRIVATE_HW -I variants/esp32_devkit_sx1262 lib_deps = ${esp32_base.lib_deps} ``` ### What this does * Uses Meshtastic’s ESP32 defaults * Targets a generic ESP32 DevKit * Marks this as private/custom hardware * Ensures your variant header is included --- ## `variant.h` (Exact Working Configuration) ```c #pragma once // Minimal custom variant for ESP32 DevKit + external SX1262 module // --- Radio selection --- #define USE_SX1262 // --- SX1262 control pins --- #define SX126X_CS 5 // NSS / CS #define SX126X_RESET 14 // NRST #define SX126X_BUSY 25 // BUSY #define SX126X_DIO1 26 // DIO1 (IRQ) // --- SPI bus (ESP32 VSPI) --- #define LORA_SCK 18 #define LORA_MOSI 23 #define LORA_MISO 19 // Compatibility with older Meshtastic code paths #define LORA_CS SX126X_CS #define LORA_DIO1 SX126X_DIO1 // Maximum safe output power for most SX1262 modules #define SX126X_MAX_POWER 22 // Enable these ONLY if your module explicitly requires them // #define SX126X_DIO3_TCXO_VOLTAGE 1.8 // #define SX126X_DIO2_AS_RF_SWITCH ``` --- ## Building the Firmware From the firmware root: ```bash pio run -e esp32_devkit_sx1262 ``` If the build complains about `mklittlefs`, install a prebuilt `mklittlefs` binary and ensure it is available in your `PATH`. --- ## Flashing the ESP32 ```bash pio run \ -e esp32_devkit_sx1262 \ -t upload \ --upload-port /dev/serial/by-id/usb-1a86_USB_Serial-if00-port0 ``` A successful flash ends with: ``` Hash of data verified. Hard resetting via RTS pin... [SUCCESS] ``` --- ## Verifying Radio Initialization Open a serial monitor: ```bash picocom -b 115200 /dev/serial/by-id/usb-1a86_USB_Serial-if00-port0 ``` Expected output: ``` SX126xInterface(cs=5, irq=26, rst=14, busy=25) SX126x init result 0 ``` If you see `init result -2`, recheck wiring. --- ## Connecting to Meshtastic ### Serial ```bash meshtastic --port /dev/serial/by-id/usb-1a86_USB_Serial-if00-port0 --info ``` ### Bluetooth * Open the Meshtastic mobile app * Connect via BLE to `Meshtastic_XXXX` --- ## Setting the Regulatory Region Always set the correct region: ```bash meshtastic --port /dev/serial/... --set lora.region EU_868 ``` --- ## Common Pitfalls * Confusing GPIO numbers with board pin labels * Leaving BUSY unconnected * Powering SX1262 from 5 V * Feeding raw battery voltage into VIN * Expecting radio pin configuration via CLI * Forgetting the antenna --- ## Final Thoughts This build gives you: * A safe battery-powered Meshtastic node * Full hardware control * A clean, maintainable firmware setup * Zero dependence on proprietary boards Once the SX1262 initializes correctly, Meshtastic is extremely stable and reliable. Happy building 🛰️