AHT20 with NUCLEO-F401RE

Wiring for the AHT20 temperature + humidity on the NUCLEO-F401RE (STM32F401RE, 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 pin.
• I2C uses the board’s default pins SDA/D14 (SDA) and SCL/D15 (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 = SDA/D14, SCL = SCL/D15 (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: STMicroelectronics:stm32:Nucleo_64:pnum=NUCLEO_F401RE. Plug the USB cable into the mini-USB port on the ST-LINK end. No button press is needed.

Questions

Which NUCLEO-F401RE pins do I use for the AHT20?

VIN → 3V3, GND → GND, SCL → SCL/D15 (PB8), SDA → SDA/D14 (PB9).

Does the AHT20 work with the NUCLEO-F401RE at 3.3 V?

Yes: the AHT20 runs at 3.3-5 V and the NUCLEO-F401RE 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 NUCLEO-F401RE 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 Raspberry Pi Pico 2 Raspberry Pi Pico W Raspberry Pi Pico Teensy 4.1

Other parts on the NUCLEO-F401RE

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