DS18B20 with Seeed XIAO ESP32C3 — waterproof probe

The DS18B20 probe is sealed in steel, so it can sit in a water tank, an aquarium or soil. On the XIAO ESP32C3 it needs one data pin — D3 — and one 4.7 kΩ pull-up to 3V3.

The sketch counts the probes on the bus at start-up and prints the first probe’s temperature every second.

Wiring

Board quirks

• D3 is GPIO5. It is the C3’s ADC2 pin, which only matters for analog readings — for a digital 1-Wire bus it is a good, boot-safe choice.
• Avoid D0, D8 and D9 for the bus: they are strapping pins, and D9 is the BOOT button.
• The XIAO’s 3V3 regulator easily powers several probes (about 1.5 mA each while converting).

Code

// DS18B20 probe on a Seeed XIAO ESP32C3.
// VDD → 3V3, DQ → D3 (GPIO5) with a 4.7 kΩ pull-up to 3V3, GND → GND.
#include <OneWire.h>
#include <DallasTemperature.h>

OneWire oneWire(D3);
DallasTemperature sensors(&oneWire);

void setup() {
  Serial.begin(115200);
  delay(1500);
  sensors.begin();
  Serial.printf("DS18B20 on D3 (GPIO5) - %u sensor(s) found\n", sensors.getDeviceCount());
}

void loop() {
  sensors.requestTemperatures();
  float t = sensors.getTempCByIndex(0);
  if (t == DEVICE_DISCONNECTED_C) Serial.println("No sensor answered - check the 4.7 kOhm pull-up");
  else Serial.printf("Temperature: %.2f C\n", t);
  delay(1000);
}

// DS18B20 probe on a Seeed XIAO ESP32C3.
// VDD → 3V3, DQ → D3 (GPIO5) with a 4.7 kΩ pull-up to 3V3, GND → GND.
#include <OneWire.h>
#include <DallasTemperature.h>

OneWire oneWire(D3);
DallasTemperature sensors(&oneWire);

void setup() {
  Serial.begin(115200);
  delay(1500);
  sensors.begin();
  Serial.printf("DS18B20 on D3 (GPIO5) - %u sensor(s) found\n", sensors.getDeviceCount());
}

void loop() {
  sensors.requestTemperatures();
  float t = sensors.getTempCByIndex(0);
  if (t == DEVICE_DISCONNECTED_C) Serial.println("No sensor answered - check the 4.7 kOhm pull-up");
  else Serial.printf("Temperature: %.2f C\n", t);
  delay(1000);
}

Library: DallasTemperature (Miles Burton (also install OneWire by Jim Studt / Paul Stoffregen)) — compiled with OneWire 2.3.8.

Expected serial output

DS18B20 on D3 (GPIO5) - 1 sensor(s) found
Temperature: 24.88 C
Temperature: 24.94 C

DS18B20 on D3 (GPIO5) - 1 sensor(s) found
Temperature: 24.88 C
Temperature: 24.94 C

Common errors