Documentation

// Capacitive Soil Moisture Sensor V1.2 - Arduino
// AOUT -> A0, VCC -> 5V, GND -> GND

const int SOIL_PIN = A0;

// Calibrate these for your sensor + soil:
const int DRY_VALUE = 590;  // raw ADC reading in dry air
const int WET_VALUE = 250;  // raw ADC reading fully submerged

void setup() {
  Serial.begin(9600);
}

void loop() {
  int raw = analogRead(SOIL_PIN);

  // Constrain and map to 0-100% (higher = wetter)
  int clamped = constrain(raw, WET_VALUE, DRY_VALUE);
  int percent = map(clamped, DRY_VALUE, WET_VALUE, 0, 100);

  Serial.print("Raw: ");
  Serial.print(raw);
  Serial.print("  Moisture: ");
  Serial.print(percent);
  Serial.println("%");

  delay(1000);
}

// Capacitive Soil Moisture Sensor V1.2 - ESP32
// AOUT -> GPIO34, VCC -> 3.3V, GND -> GND

const int SOIL_PIN = 34;

// 12-bit ADC: 0-4095. Calibrate these:
const int DRY_VALUE = 3000;
const int WET_VALUE = 1200;

void setup() {
  Serial.begin(115200);
  analogReadResolution(12);
  analogSetAttenuation(ADC_11db); // full 0-3.3V range
}

void loop() {
  int raw = analogRead(SOIL_PIN);
  int clamped = constrain(raw, WET_VALUE, DRY_VALUE);
  int percent = map(clamped, DRY_VALUE, WET_VALUE, 0, 100);

  Serial.printf("Raw: %d  Moisture: %d%%\n", raw, percent);
  delay(1000);
}

# Capacitive Soil Moisture Sensor V1.2 - Raspberry Pi
# Requires an MCP3008 ADC over SPI.
# pip install adafruit-circuitpython-mcp3xxx

import time
import board
import busio
import digitalio
from adafruit_mcp3xxx.mcp3008 import MCP3008
from adafruit_mcp3xxx.analog_in import AnalogIn

spi = busio.SPI(clock=board.SCK, MISO=board.MISO, MOSI=board.MOSI)
cs = digitalio.DigitalInOut(board.D8)
mcp = MCP3008(spi, cs)
chan = AnalogIn(mcp, 0)  # MCP3008 CH0

# Calibrate (0-65535 scale from adafruit lib)
DRY_VALUE = 48000
WET_VALUE = 20000

while True:
    raw = chan.value
    clamped = max(WET_VALUE, min(DRY_VALUE, raw))
    percent = int((DRY_VALUE - clamped) * 100 / (DRY_VALUE - WET_VALUE))
    print(f"Raw: {raw}  Voltage: {chan.voltage:.2f}V  Moisture: {percent}%")
    time.sleep(1)

# Capacitive Soil Moisture Sensor V1.2 - Pico (MicroPython)
# AOUT -> GP26 (ADC0), VCC -> 3V3, GND -> GND

from machine import ADC, Pin
import time

soil = ADC(Pin(26))

# 16-bit value on Pico (read_u16). Calibrate:
DRY_VALUE = 50000
WET_VALUE = 22000

while True:
    raw = soil.read_u16()
    clamped = max(WET_VALUE, min(DRY_VALUE, raw))
    percent = int((DRY_VALUE - clamped) * 100 / (DRY_VALUE - WET_VALUE))
    print("Raw:", raw, " Moisture:", percent, "%")
    time.sleep(1)