Stuff that sits in the Hardware Hack Lab Barcelona.

A NodeMCU (ESP8266) connected to a range sensor (HC-SR04)

Here are the two tutorials that got me this circuit wired properly:

• Using the HC-SR04 Ultrasonic Distance Sensor with Arduino
• GPIO map for NodeMCU
• NodeMCU AMica

The key difference with these tutorials and other tutorials found online explaining the same process:

• The GPIO pins are differently ordered on an ESP6288 than on an Arduino.
• Most tutorials with the ESP8266 and HC-SR04 tell you to connect the sensor to 3.3V output from the NodeMCU board, but that did not work at all for me. Connecting to the Vin output port worked because it delivers 5V or close.

Here is the functioning code I used (it requires installation of NewPing library in Arduino IDE):

/*
  HC-SR04 Basic Demonstration
  HC-SR04-Basic-Demo.ino
  Demonstrates functions of HC-SR04 Ultrasonic Range Finder
  Displays results on Serial Monitor
 
 
  Details: https://dronebotworkshop.com/hc-sr04-ultrasonic-distance-sensor-arduino/
  GPIO map for NodeMCU: https://nodemcu.readthedocs.io/en/master/modules/gpio/
 
 
*/
 
// Include NewPing Library
#include <NewPing.h>
 
#define trigPin 2
#define echoPin 0
#define MAX_DISTANCE 400
 
NewPing sonar(trigPin, echoPin, MAX_DISTANCE);
 
float duration, distance;
int iterations = 5;
 
void setup() {
  Serial.begin (9600);
}
 
void loop() {
 
  duration = sonar.ping_median(iterations);
 
  // Determine distance from duration
  // Use 343 metres per second as speed of sound
 
  distance = (duration / 2) * 0.0343;
 
  // Send results to Serial Monitor
  Serial.print("Distance = ");
  if (distance >= 400 || distance <= 2) {
    Serial.println("Out of range");
  }
  else {
    Serial.print(distance);
    Serial.println(" cm");
    delay(500);
  }
  delay(500);
}