d7main/ESP32_EnvironmentalNode: eSP32-C3 Environmental Monitoring Node (ESP-IDF)

A low-power environmental monitoring firmware built with native ESP-IDF v5.x and PlatformIO (no Arduino framework). Wakes from Deep Sleep, reads sensors, evaluates a configurable soil moisture threshold, dispatches alerts over one or more webhook channels, and returns to sleep.

An on-demand SoftAP Web Portal — launched by holding a physical button — handles all runtime configuration without serial re-flashing.

Hardware & Screenshots

Web Configurator UI	Hardware MVP	Wiring Schematic

Features

• Pure ESP-IDF v5.x — no Arduino wrappers, no bloat.
• Deep Sleep — timer wakeup via RTC; configurable interval (DEFAULT_SLEEP_SEC, default 30 min).
• On-Demand Web Portal — hold GPIO9 (BOOT button) ≥ 3 s to launch the SoftAP configurator at 192.168.4.1. Live sensor telemetry updates every 7 s while the portal is open.
• Multi-Channel Alerts — Telegram Bot API, Discord Webhook, and Custom JSON Webhook. Each channel is independent; a failed channel does not block the others.
• Configurable Threshold — soil alert threshold (%) stored in NVS, adjustable via the portal.
• NVS Persistence — Wi-Fi credentials, notification tokens/URLs, ADC calibration bounds, and alert threshold survive power cycles.
• Sensors — capacitive soil moisture (ADC), BMP280 (I²C, temperature + pressure), DHT22 (1-Wire, temperature + humidity).

Target Hardware

GPIO assignments are defined in include/config.h and selectable per target via build_flags in platformio.ini.

Strapping pin note: GPIO2 on ESP32-C3 controls boot mode. Pulling it LOW during power-on enters JTAG/download mode. Use GPIO9 (BOOT button) for the config trigger instead — it is safe to hold LOW at any time.

Quick Start

Prerequisites

• PlatformIO Core or the VS Code PlatformIO extension
• USB cable to ESP32-C3 dev board

Build

git clone https://github.com/your-username/ESP32_EnvironmentalNode.git
cd ESP32_EnvironmentalNode
pio run --environment esp32_c3

Upload & Monitor

pio run --target upload --target monitor --environment esp32_c3

Monitor baud rate: 115200.

First-Time Setup

1. Flash the firmware. On first boot is_configured = false, so the device immediately launches the SoftAP.
2. Connect a phone or laptop to Wi-Fi SSID d7main_sensor (password: admin123).
3. Open http://192.168.4.1 in a browser.
4. Fill in the form and click Write to NVS & Reboot:

To re-enter the portal at any time: hold GPIO9 (BOOT button) for ≥ 3 seconds.

Sensor Calibration

The moisture percentage is computed linearly from two ADC calibration points:

moisture_pct = (v_dry - soil_mv) * 100 / (v_dry - v_wet)

Typical values: v_dry ≈ 2600 mV, v_wet ≈ 1200 mV (varies by sensor and supply voltage).

Alert Channels

Telegram

Requires a bot token and chat ID. Alert text is sent as a text message via sendMessage.

Discord Webhook

POST to the configured URL with:

{ "content": "<alert message>" }

Custom Webhook

POST to the configured URL with a full sensor payload:

{
  "event":    "alert",
  "message":  "Low soil moisture alert!\nMoisture: 18% ...",
  "soil_mv":  2350,
  "temp":     23.1,
  "humidity": 58.0
}

All channels: Content-Type: application/json, 6-second timeout per request.

Firmware Boot Cycle

Power on / Deep Sleep wakeup
│
├─ NVS init → load config
├─ is_configured?
│   ├─ No  → launch SoftAP + Web Portal (blocks until form submit + reboot)
│   └─ Yes →
│       ├─ Spawn button monitor task (GPIO9 hold = portal escape hatch)
│       ├─ Read sensors (soil ADC, BMP280, DHT22)
│       ├─ Calculate moisture %
│       ├─ Connect Wi-Fi STA
���       │   ├─ moisture < threshold → sys_alerts_send() [Telegram / Discord / Custom]
│       │   └─ moisture OK         → log, skip alerts
│       └─ Deep Sleep (DEFAULT_SLEEP_SEC = 1800 s)

NVS Key Map

NVS namespace: storage (see NVS_NAMESPACE in config.h).

Project Structure

ESP32_EnvironmentalNode/
├── include/
│   ├── config.h          # GPIO map, sleep interval, AP credentials
│   ├── sys_nvs.h         # Config struct + NVS API
│   ├── sys_wifi.h        # Wi-Fi, Web Portal, sys_alerts_send()
│   ├── hal_bmp280.h
│   ├── hal_dht22.h
│   ├── hal_i2c.h
│   └── hal_moisture.h
├── src/
│   ├── main.c            # App entry, boot cycle, operational loop
│   ├── sys_nvs.c         # NVS load/save
│   ├── sys_wifi.c        # AP/STA, HTTP server, alert dispatch
│   ├── hal_bmp280.c
│   ├── hal_dht22.c
│   ├── hal_i2c.c
│   └── hal_moisture.c
├── partitions.csv        # Custom partition table (2 MB flash)
└── platformio.ini