Walter Field Node

LonePeak Radio LLC -- ESP32-S3 Cellular IoT Sensor Platform

Production firmware for the Walter Field Node -- a solar/battery-powered remote sensor platform built on the DPTechnics Walter (ESP32-S3 + Sequans GM02SP cellular modem). Deployed in the field monitoring a trailer in Utah.

What It Does

• Reads DS18B20 temperature probe on GPIO12
• Reads 0-25V trailer battery voltage on GPIO4
• Reads BME680 environmental sensor (temp, humidity, pressure, gas, air quality)
• Sends all readings as JSON telemetry via UDP every 15 minutes
• Primary transport: LTE cellular via Soracom
• Failover transport: WiFi UDP to same relay server with identical payload
• Serves a local captive portal dashboard over WiFi AP with auto-refresh
• Login-gated dashboard showing signal bars, sensor readings, uplink stats

Hardware

• MCU: DPTechnics Walter (ESP32-S3 + Sequans GM02SP cellular modem)
• Temperature: DS18B20 waterproof probe on GPIO12
• Battery monitor: 0-25V sensor module on GPIO4
• Environment: BME680 on I2C (SDA=GPIO8, SCL=GPIO9, addr 0x76)
• Cellular: LTE-M / NB-IoT via Soracom
• Power: Solar + 12V trailer battery

Wiring

DS18B20: Red -> 3V3 Black -> GND Yellow -> GPIO12 4.7k resistor between Yellow and Red (REQUIRED)

0-25V Battery Sensor: S (signal) -> GPIO4 VCC -> 3V3 GND -> GND Screw+ -> Battery positive Screw- -> Battery negative

BME680: VCC -> 3V3 GND -> GND SDA -> GPIO8 SCL -> GPIO9 CS -> 3V3 (selects I2C mode) SDO -> GND (selects address 0x76)

Telemetry JSON Fields

tc - ESP32 CPU silicon temperature C ds - DS18B20 probe temperature C vb - Trailer battery voltage V bme_t - BME680 temperature C bme_h - BME680 humidity percent RH bme_p - BME680 pressure hPa bme_g - BME680 gas resistance ohms rsrp - LTE signal power dBm rssi - LTE signal strength dBm up - Uptime seconds since boot op - Cellular operator name seq - Transmission sequence number

Setup

1. Install Arduino IDE
2. Install ESP32 board package
3. Install libraries via Arduino Library Manager:
   • OneWire by Paul Stoffregen
   • DallasTemperature by Miles Burton
   • Adafruit BME680
   • Adafruit Unified Sensor
   • WalterModem by DPTechnics
4. Copy src/config.h.example to src/config.h
5. Fill in your WiFi credentials, APN, and relay server details
6. Flash to Walter via USB

NOTE: config.h is excluded from git.

Changelog

v1.12 - WiFi telemetry failover. Cellular primary, WiFi UDP fallback. New debug counters txCell/txWifi/txFail and uplink status on dashboard. v1.11 - BME680 environmental sensor on I2C. Non-blocking state machine. New JSON fields bme_t, bme_h, bme_p, bme_g. New dashboard card. v1.10 - 0-25V trailer battery sensor on GPIO4. New vb field in JSON. v1.09 - DS18B20 temperature probe on GPIO12. Non-blocking 12-bit reads. v1.08 - UDP telemetry upload to Linode relay server. v1.07b - setRAT AUTO to clear stuck NB-IoT.

License

GNU General Public License v3.0