Looking to measure distance using ESP32? The HC-SR04 Ultrasonic Sensor is a fantastic module for beginners and professionals alike. In this tutorial, we’ll guide you step-by-step on how to interface this sensor with an ESP32 development board using ESP-IDF. You’ll learn how the sensor works, how to connect it, and how to write the firmware to get distance measurements.
📦 Components Required
To get started, you’ll need the following components:
- ✅ ESP32 Development Board
- ✅ HC-SR04 Ultrasonic Sensor
- ✅ Micro USB Cable
- ✅ M2M Jumper Wires
- ✅ Breadboard
🧠 Understanding HC-SR04 Sensor
The HC-SR04 ultrasonic sensor is a popular device. It is cost-effective. It is used for measuring distance by utilizing the principles of sound wave reflection. It operates using the time-of-flight method. This method calculates the time it takes for sound waves to travel to an object and bounce back.
- VCC – Power supply (5V)
- Trig – Trigger pulse input
- Echo – Echo pulse output
- GND – Ground
🚀 Working Principle:
- Trigger Initiation: When the Trigger pin receives a 10µs HIGH signal, it emits a short burst of ultrasonic sound. This consists of 8 pulses at 40 kHz.
- Wave Propagation: The ultrasonic waves travel through the air until they hit an object.
- Echo Reception: Once the waves hit an object, they bounce back and are received by the sensor’s Echo pin.
- Time Measurement: The time between sending and receiving the pulse is measured in microseconds.
- Distance Calculation:
The distance to the object is calculated using the formula:
Distance (cm)=(Time (µs)×0.0343)/2
○ 0.0343 cm/µs is the speed of sound in air.
○ The time is divided by 2 because it covers both the forward and return trip.
📏 Example:
If the Echo pin remains HIGH for 500 µs, the distance is:
500×0.03432/2=8.575 cm
This real-time, accurate, and non-contact distance measurement makes the HC-SR04 ideal for robotics, object avoidance, water level monitoring, and more.
It measures distances from 2 cm to 400 cm with a precision of about 3 mm.
🔌 Circuit Connections
| HC-SR04 Pin | ESP32 GPIO |
|---|---|
| VCC | 5V(VIN) |
| GND | GND |
| Trig | GPIO 5 |
| Echo | GPIO 18 |
Tip: Use a voltage divider if you’re cautious about 5V on ESP32’s GPIOs. In many cases, the echo pin works reliably when connected directly to a 3.3V-compatible GPIO, but safety first!
🧰 ESP-IDF Project Structure
We’ll use the ESP-IDF framework to code the firmware. Make sure ESP-IDF is installed and set up.
idf.py create-project ultrasonic_sensor
cd ultrasonic_sensor
💻 Writing the Code
Here is the full C code to read distance using HC-SR04:
#include <stdio.h>
#include <stdbool.h>
#include <freertos/FreeRTOS.h>
#include <freertos/task.h>
#include <ultrasonic.h>
#include <esp_err.h>
#define MAX_DISTANCE_CM 500 // 5m max
#define TRIGGER_GPIO 5
#define ECHO_GPIO 18
void ultrasonic_test(void *pvParameters)
{
ultrasonic_sensor_t sensor = {
.trigger_pin = TRIGGER_GPIO,
.echo_pin = ECHO_GPIO
};
ultrasonic_init(&sensor);
while (true)
{
float distance;
esp_err_t res = ultrasonic_measure(&sensor, MAX_DISTANCE_CM, &distance);
if (res != ESP_OK)
{
printf("Error %d: ", res);
switch (res)
{
case ESP_ERR_ULTRASONIC_PING:
printf("Cannot ping (device is in invalid state)\n");
break;
case ESP_ERR_ULTRASONIC_PING_TIMEOUT:
printf("Ping timeout (no device found)\n");
break;
case ESP_ERR_ULTRASONIC_ECHO_TIMEOUT:
printf("Echo timeout (i.e. distance too big)\n");
break;
default:
printf("%s\n", esp_err_to_name(res));
}
}
else
printf("Distance: %0.04f cm\n", distance*100);
vTaskDelay(pdMS_TO_TICKS(500));
}
}
void app_main()
{
xTaskCreate(ultrasonic_test, "ultrasonic_test", configMINIMAL_STACK_SIZE * 3, NULL, 5, NULL);
}
Download the full code here.
🔧 Building and Flashing the Code
To build and flash the code:
idf.py build
idf.py -p /dev/ttyUSB0 flash
idf.py monitor
Make sure to replace /dev/ttyUSB0 with your actual serial port. The port will be different(like COM3, COM4, etc) if you are working on windows OS
🎯 Expected Output
After uploading the firmware and opening the serial monitor, you should see distance readings printed every second like this:
Distance: 17.32 cm
Distance: 18.04 cm
Distance: 17.58 cm
This confirms that your sensor is working correctly!
Also, watch this video to get the clear understand on how to do it practically with zero error ratio.
🎓 Conclusion
Congratulations! You’ve successfully interfaced the HC-SR04 ultrasonic sensor with the ESP32 using ESP-IDF. This foundational setup opens up many project possibilities—from robot navigation to smart parking sensors.
👉 Need Components?
You can grab all the components used in this project from the links below:
💬 Got Questions?
Leave a comment below if you’re stuck or have suggestions! You can also check out our YouTube tutorial on this same project.
Let’s innovate together — one sensor at a time!
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