ESP32 LoRaWAN Industrial Node

Industrial low-power telemetry boilerplate for ESP32 + LoRa-E5 + ADS1115.
4-20 mA acquisition, compact binary payload, LoRaWAN uplink, immediate deep sleep.

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Overview

This repository provides a production-oriented firmware foundation for industrial IoT nodes where energy budget and deterministic behavior matter.

Each wake cycle does exactly one job:

1. Wake from deep sleep (15-minute interval)
2. Read a 4-20 mA loop through ADS1115
3. Convert to engineering units (0-100 psi)
4. Pack data into a 4-byte binary payload
5. Send LoRaWAN uplink through Seeed LoRa-E5 (AT modem)
6. Enter deep sleep immediately after TX completion

No JSON, no String, no delay() loops.

Why AT Modem (LoRa-E5) Instead of LMIC

The Seeed LoRa-E5 module already contains an STM32WLE5 and integrated LoRaWAN stack.

For this hardware profile, the correct architecture is:

• ESP32 handles sensing and system orchestration
• LoRa-E5 handles LoRaWAN via UART AT commands

MCCI LMIC is generally used when the ESP32 directly drives a raw LoRa transceiver (e.g., SX127x/SX126x over SPI).

Key Features

• Non-blocking event-driven finite state machine
• Deep sleep first design (battery-focused)
• ADS1115 high-resolution acquisition over I2C
• Compact big-endian payload encoding
• Retry strategy for join/uplink with bounded attempts
• Doxygen-style inline code documentation

Hardware Configuration

ESP32 <-> ADS1115 (I2C)

• GPIO21 -> SDA
• GPIO22 -> SCL
• ADS1115 address: 0x48
• Input channel: A0

ESP32 <-> LoRa-E5 (UART2)

• GPIO16 <- LoRa-E5 TX
• GPIO17 -> LoRa-E5 RX
• UART baudrate: 9600

4-20 mA Front-end

Default shunt resistor in code:

• Rshunt = 165R (0.1% recommended)
• 4 mA -> ~0.66 V
• 20 mA -> ~3.30 V

Engineering conversion:

• I(mA) = Vshunt / Rshunt * 1000
• psi = clamp((I - 4) / 16, 0..1) * 100

Payload Specification

Uplink payload size: 4 bytes (big-endian)

Bytes	Field	Unit	Scale
0..1	Pressure	psi	value / 100
2..3	Loop current	mA	value / 100

Example decoding:

• 0x1388 -> 50.00 psi
• 0x07D0 -> 20.00 mA

State Machine

stateDiagram-v2
  [*] --> ModemPing
  ModemPing --> ModemSetMode
  ModemSetMode --> ModemSetRegion
  ModemSetRegion --> ModemSetAdr
  ModemSetAdr --> ModemSetPort
  ModemSetPort --> ModemSetAppEui
  ModemSetAppEui --> ModemSetDevEui
  ModemSetDevEui --> ModemSetAppKey
  ModemSetAppKey --> ModemJoin
  ModemJoin --> SensorStartConversion
  ModemJoin --> JoinRetryWait
  JoinRetryWait --> ModemJoin
  SensorStartConversion --> SensorWaitConversion
  SensorWaitConversion --> SendUplink
  SendUplink --> EnterSleep
  SendUplink --> UplinkRetryWait
  UplinkRetryWait --> ModemJoin
  UplinkRetryWait --> SendUplink
  EnterSleep --> [*]

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Repository Layout

• src/main.cpp: firmware state machine and integration logic
• platformio.ini: board setup, dependencies, build-time credentials
• docs/hardware.md: wiring and electrical integration notes
• docs/commissioning.md: LoRaWAN OTAA provisioning checklist
• docs/power-optimization.md: power and autonomy guidance
• docs/payload-decoder.js: payload decoder for TTN / ChirpStack
• docs/assets/industrial-node-logo.svg: README visual asset

Quick Start

1. Configure OTAA credentials

Edit platformio.ini build flags:

• LORAE5_REGION
• LORAE5_APP_EUI
• LORAE5_DEV_EUI
• LORAE5_APP_KEY
• LORAE5_UPLINK_PORT

2. Build and flash

pio run
pio run -t upload
pio device monitor

3. Validate runtime sequence on serial monitor

Expected command flow:

• AT
• AT+MODE=LWOTAA
• AT+DR=<REGION>
• AT+ID=AppEui,...
• AT+ID=DevEui,...
• AT+KEY=APPKEY,...
• AT+JOIN
• AT+MSGHEX="..."

Successful uplink ends with +MSGHEX: Done, then the node enters deep sleep.

Network Decoder

Use payload-decoder.js in The Things Stack or adapt it for ChirpStack to decode the 4-byte uplink into:

• pressure_psi
• loop_current_ma

Power Optimization Notes

• Wakeup interval defaults to 15 minutes (esp_sleep timer)
• TX completion leads directly to deep sleep transition
• AT+LOWPOWER is sent to the LoRa-E5 before sleeping (best effort)
• Bounded retry policy prevents uncontrolled active-time growth

Recommended Next Improvements

• Persist a lightweight session state strategy to reduce OTAA joins in battery deployments
• Add supply-voltage measurement so the uplink can include node health, not just process value
• Add a production secrets override flow for CI/local builds instead of editing credentials inline
• Add calibration constants for the analog front-end to compensate resistor and sensor tolerance

Useful References

• Seeed LoRa-E5 product page
• Seeed LoRa-E5 AT Command Specification (PDF)

License

This project is released under the MIT License.