PlantSensor

ESP32-C3 LoRa plant monitor. Wakes every 15 minutes from deep sleep, reads soil moisture (capacitive), ambient light (LDR), temperature and humidity (DHT11), then transmits via LoRa 868 MHz to a combined receiver (MailboxSensor).

Features

• Deep sleep between readings (15 min interval, configurable)
• Sequence number persisted across deep sleep via RTC_DATA_ATTR
• ACK protocol — waits for receiver acknowledgment
• RGB LED status blinks (red = dry/dark, yellow = ok, green = good)
• Calibration constants for soil sensor (dry/wet raw ADC values)
• Packet format: P,<seq>,<batteryMv>,<soilRaw>,<lightRaw>,<tempCx10>,<humPct>

Hardware

Component	GPIO
Capacitive soil sensor	0 (ADC)
DHT11	1
LDR	2 (ADC)
LoRa SCK	4
LoRa MISO	5
LoRa MOSI	6
LoRa SS	7
LoRa RST	8
LoRa DIO0	3
LED Red	9
LED Green	10

Sensor Calibration

Edit these constants in Plant_sensor.ino to match your soil sensor:

const int SOIL_DRY   = 2876;  // ADC reading in dry air
const int SOIL_WET   = 1941;  // ADC reading fully submerged
const int LIGHT_DARK   = 4095;
const int LIGHT_BRIGHT = 1130;

Setup

Flash Plant_sensor/Plant_sensor.ino to an ESP32-C3.

FQBN

esp32:esp32:esp32c3

Libraries required

• LoRa by Sandeep Mistry
• DHT sensor library by Adafruit
• SPI (bundled with ESP32 Arduino core)

Home Assistant

Data is received and published to MQTT by the MailboxSensor receiver node, which includes full MQTT auto-discovery for plant entities (soil %, light %, temperature, humidity, battery, RSSI).