Capacitive soil moisture sensor with Raspberry Pi Pico

Wiring for the Capacitive soil moisture sensor v1.2 on the Raspberry Pi Pico (RP2040, 3.3 V logic), chosen with the same pin rules BoardPilot uses: default buses first, and no pins that are used for flash, USB, the debugger or booting.

Wiring

Check before you power it on

• Supply: 3.3 V from the 3V3(OUT) pin.

Good to know

• The reading depends on your soil and supply voltage. Note the values in dry air and in water, and scale between them. (DFRobot SEN0193 capacitive soil moisture sensor wiki, Calibration)

Test code (Arduino)

void setup() {
  Serial.begin(115200);
  analogReadResolution(12);
}

void loop() {
  long mv = (long)analogRead(26) * 3300L / 4095;  // AOUT on GP26
  Serial.println(mv);
  delay(200);
}

Arduino board: rp2040:rp2040:rpipico. If the board is not found, hold the BOOTSEL button while plugging in the USB cable.

Questions

Which Raspberry Pi Pico pins do I use for the Capacitive soil moisture sensor?

GND → GND, VCC → 3V3(OUT), AOUT → GP26.

Does the Capacitive soil moisture sensor work with the Raspberry Pi Pico at 3.3 V?

Yes: the Capacitive soil moisture sensor runs at 3.3-5 V and the Raspberry Pi Pico uses 3.3 V signals, so no level shifting is needed.

Full Raspberry Pi Pico pinout · Capacitive soil moisture sensor v1.2: all pins and data

The Capacitive soil moisture sensor on other boards

ESP32 DevKit Arduino Mega 2560 R3 Arduino Nano Arduino Uno R3 WeAct Black Pill STM32F411CE ESP32-C3-DevKitM-1 ESP32-S3-DevKitC-1 Nordic nRF52840 DK NUCLEO-F401RE Raspberry Pi Pico 2 Raspberry Pi Pico W Teensy 4.1

Other parts on the Raspberry Pi Pico

BME280 BMP280 DHT22 DHT11 HC-SR04 SSD1306 OLED MPU6050 DS18B20 WS2812B LED strip SG90 servo Relay module HC-SR501 PIR LCD 1602 I2C INA219 VL53L0X BH1750 MAX30102 RC522 RFID NEO-6M GPS ADS1115 TM1637 28BYJ-48 stepper L298N Potentiometer Push button LED Joystick module SD card module AHT20

Learn the basics

Lesson: ADC: reading the analog world ADC (analog-to-digital converter)