HC-SR04 ultrasonic distance with ESP32

Supply 5 V Bus GPIO Measures distance

Pins and ESP32 wiring

Pin	Role	ESP32 pin	Notes
VCC	Power	VIN	Needs 5 V: use VIN
TRIG	Input (the ESP32 drives it)	D25	A 10 µs HIGH pulse starts a measurement
ECHO	Output (the part drives it)	D26	Outputs 5 V: use a voltage divider (e.g. 1 kΩ + 2 kΩ) before the ESP32 pin
GND	Ground	GND

Suggested wiring for the 30-pin ESP32 DevKit, avoiding flash, input-only and strapping pins. BoardPilot checks it for you as you wire.

This module is sold for 5 V. Its outputs may be 5 V: use a level shifter or a voltage divider on ESP32 inputs.

on 3.3 V boards: ECHO outputs 5 V. On a 3.3 V board, put a voltage divider (for example 1 kΩ and 2 kΩ) between ECHO and the pin. (Cytron / ElecFreaks HC-SR04 user manual, Electric parameters: working voltage DC 5 V)
It needs 5 V on VCC. At 3.3 V most modules give no echo or wrong distances. (Cytron / ElecFreaks HC-SR04 user manual, Electric parameters: working voltage DC 5 V)
Leave at least 60 ms between measurements, or the echo of the last one is measured again. (Cytron / ElecFreaks HC-SR04 user manual, Timing diagram: measurement cycle over 60 ms)

Cytron / ElecFreaks HC-SR04 user manual, Pins VCC, Trig, Echo, GND; 10 µs trigger pulse; 5 V supply

Part data: CC BY 4.0, free to reuse with credit to BoardPilot.