AHT20 with Raspberry Pi Pico

Wiring for the AHT20 temperature + humidity 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.
• I2C uses the board’s default pins GP4 (SDA) and GP5 (SCL). Most modules include pull-up resistors; if the part is not found, check them and swap-test SDA/SCL.

Test code (Arduino)

#include <Wire.h>

void setup() {
  Serial.begin(115200);
  Wire.begin();  // SDA = GP4, SCL = GP5 (the board's default I2C pins)
  Wire.beginTransmission(0x38);
  bool found = Wire.endTransmission() == 0;
  Serial.println(found ? "AHT20 temperature + humidity found at 0x38" : "Not found: check power, GND and SDA/SCL");
}

void loop() {}

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 AHT20?

VIN → 3V3(OUT), GND → GND, SCL → GP5, SDA → GP4.

Does the AHT20 work with the Raspberry Pi Pico at 3.3 V?

Yes: the AHT20 runs at 3.3-5 V and the Raspberry Pi Pico uses 3.3 V signals, so no level shifting is needed.

What is the I2C address of the AHT20?

0x38. An I2C scan (BoardPilot does it for you) shows which one your module uses.

Full Raspberry Pi Pico pinout · AHT20 temperature + humidity: all pins and data

The AHT20 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

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