HC-SR04 with NUCLEO-F401RE

Wiring for the HC-SR04 ultrasonic distance 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

HC-SR04 pin	Role	NUCLEO-F401RE pin	Notes
VCC	Power	5V	Needs 5 V: use 5V
TRIG	Input to the part	D2 (PA10)	A 10 µs HIGH pulse starts a measurement
ECHO	Output from the part	D4 (PB5)
GND	Ground	GND

Check before you power it on

Supply: 5 V from the 5V pin.
The HC-SR04 works at 5 V. On the NUCLEO-F401RE, D4 tolerate 5 V inputs, so a direct connection is fine while the board is powered.

Test code (Arduino)

void setup() {
  Serial.begin(115200);
  pinMode(PA10, OUTPUT);  // TRIG on D2
  pinMode(PB5, INPUT);   // ECHO on D4
}

void loop() {
  digitalWrite(PA10, LOW);  delayMicroseconds(2);
  digitalWrite(PA10, HIGH); delayMicroseconds(10);
  digitalWrite(PA10, LOW);
  long us = pulseIn(PB5, HIGH, 30000);
  Serial.println(us / 58.0);  // distance in cm
  delay(200);
}

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 HC-SR04?

VCC → 5V, TRIG → D2 (PA10), ECHO → D4 (PB5), GND → GND.

Does the HC-SR04 work with the NUCLEO-F401RE at 3.3 V?

Yes: the HC-SR04 runs at 5 V and the NUCLEO-F401RE uses 3.3 V signals, so no level shifting is needed.

BoardPilot checks this wiring in 3D as you build it, and finds crossed or missing wires on the real board.

Download BoardPilot

Full NUCLEO-F401RE pinout · HC-SR04 ultrasonic distance: all pins and data

The HC-SR04 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

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