HC-SR04 with Raspberry Pi Pico

Wiring for the HC-SR04 ultrasonic distance 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

HC-SR04 pin	Role	Raspberry Pi Pico pin	Notes
VCC	Power	VBUS	Needs 5 V: use VBUS
TRIG	Input to the part	GP15	A 10 µs HIGH pulse starts a measurement
ECHO	Output from the part	GP14
GND	Ground	GND

Check before you power it on

Supply: 5 V from the VBUS pin.
The HC-SR04 works at 5 V, so its output (ECHO → GP14) can reach 5 V. The Raspberry Pi Pico pins take only 3.3 V: add a voltage divider (for example 1 kΩ and 2 kΩ) or a level shifter on that wire.

Test code (Arduino)

void setup() {
  Serial.begin(115200);
  pinMode(15, OUTPUT);  // TRIG on GP15
  pinMode(14, INPUT);   // ECHO on GP14
}

void loop() {
  digitalWrite(15, LOW);  delayMicroseconds(2);
  digitalWrite(15, HIGH); delayMicroseconds(10);
  digitalWrite(15, LOW);
  long us = pulseIn(14, HIGH, 30000);
  Serial.println(us / 58.0);  // distance in cm
  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 HC-SR04?

VCC → VBUS, TRIG → GP15, ECHO → GP14, GND → GND.

Does the HC-SR04 work with the Raspberry Pi Pico at 3.3 V?

The HC-SR04 works at 5 V, so its output (ECHO → GP14) can reach 5 V. The Raspberry Pi Pico pins take only 3.3 V: add a voltage divider (for example 1 kΩ and 2 kΩ) or a level shifter on that wire.

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

Download BoardPilot

Full Raspberry Pi Pico pinout · HC-SR04 ultrasonic distance: all pins and data

The HC-SR04 on other boards

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