Documentation

// HC-SR04 with RGB Light:
// - Trigger on D2, Echo on D3
// - RGB_IN on D6 (4 WS2812B pixels onboard)
// - Prints distance over Serial and colors LEDs by range.

#include <Adafruit_NeoPixel.h>

#define TRIG_PIN   2
#define ECHO_PIN   3
#define LED_PIN    6
#define NUM_LEDS   4

Adafruit_NeoPixel strip(NUM_LEDS, LED_PIN, NEO_GRB + NEO_KHZ800);

void setup() {
  pinMode(TRIG_PIN, OUTPUT);
  pinMode(ECHO_PIN, INPUT);
  digitalWrite(TRIG_PIN, LOW);
  strip.begin();
  strip.setBrightness(40);  // 0-255; keep low to avoid overheating
  strip.show();
  Serial.begin(9600);
}

float readDistanceCm() {
  digitalWrite(TRIG_PIN, LOW);  delayMicroseconds(2);
  digitalWrite(TRIG_PIN, HIGH); delayMicroseconds(10);
  digitalWrite(TRIG_PIN, LOW);

  unsigned long duration = pulseIn(ECHO_PIN, HIGH, 30000UL);
  if (duration == 0) return -1;  // timeout / out of range
  return duration * 0.0343f / 2.0f;
}

void setAll(uint8_t r, uint8_t g, uint8_t b) {
  for (int i = 0; i < NUM_LEDS; i++) strip.setPixelColor(i, r, g, b);
  strip.show();
}

void loop() {
  float cm = readDistanceCm();
  Serial.print("Distance: ");
  Serial.print(cm);
  Serial.println(" cm");

  if (cm < 0)        setAll(0, 0, 50);     // no echo = blue
  else if (cm < 15)  setAll(255, 0, 0);    // very close = red
  else if (cm < 50)  setAll(255, 120, 0);  // mid = orange
  else                setAll(0, 200, 0);    // far = green

  delay(80);
}

# Install: sudo pip3 install rpi_ws281x --break-system-packages
# Run:     sudo python3 hcsr04_rgb.py
# Wiring:  Trig=GPIO23, Echo=GPIO24 (via divider), RGB_IN=GPIO18 (via shifter).

import time
import RPi.GPIO as GPIO
from rpi_ws281x import PixelStrip, Color

TRIG = 23
ECHO = 24

NUM_LEDS  = 4
LED_PIN   = 18        # must be PWM-capable
LED_FREQ  = 800000
LED_DMA   = 10
LED_INV   = False
LED_BRT   = 40
LED_CH    = 0

strip = PixelStrip(NUM_LEDS, LED_PIN, LED_FREQ, LED_DMA, LED_INV, LED_BRT, LED_CH)
strip.begin()

GPIO.setmode(GPIO.BCM)
GPIO.setup(TRIG, GPIO.OUT, initial=GPIO.LOW)
GPIO.setup(ECHO, GPIO.IN)

def ping_cm():
    GPIO.output(TRIG, True); time.sleep(1e-5); GPIO.output(TRIG, False)
    t0 = time.time()
    while GPIO.input(ECHO) == 0 and time.time() - t0 < 0.03: start = time.time()
    while GPIO.input(ECHO) == 1 and time.time() - t0 < 0.06: stop  = time.time()
    try:
        return (stop - start) * 17150.0
    except UnboundLocalError:
        return -1.0

def set_all(color):
    for i in range(NUM_LEDS):
        strip.setPixelColor(i, color)
    strip.show()

try:
    while True:
        cm = ping_cm()
        print(f"Distance: {cm:.1f} cm")
        if cm < 0:        set_all(Color(0, 0, 50))
        elif cm < 15:     set_all(Color(255, 0, 0))
        elif cm < 50:     set_all(Color(255, 120, 0))
        else:             set_all(Color(0, 200, 0))
        time.sleep(0.1)
except KeyboardInterrupt:
    set_all(Color(0, 0, 0))
    GPIO.cleanup()

# Uses a ready-made NeoPixel driver (e.g. 'neopixel' module on MicroPython).
# Wiring: Trig=GP2, Echo=GP3 (via divider), RGB_IN=GP6 (via shifter).

from machine import Pin, time_pulse_us
import time, neopixel

TRIG = Pin(2, Pin.OUT)
ECHO = Pin(3, Pin.IN)

NUM_LEDS = 4
np = neopixel.NeoPixel(Pin(6), NUM_LEDS)

def ping_cm():
    TRIG.value(0); time.sleep_us(2)
    TRIG.value(1); time.sleep_us(10); TRIG.value(0)
    us = time_pulse_us(ECHO, 1, 30_000)
    return -1 if us <= 0 else (us / 58.0)

def set_all(r, g, b):
    for i in range(NUM_LEDS):
        np[i] = (r, g, b)
    np.write()

while True:
    cm = ping_cm()
    print("Distance:", cm, "cm")
    if cm < 0:        set_all(0, 0, 30)
    elif cm < 15:     set_all(60, 0, 0)
    elif cm < 50:     set_all(60, 30, 0)
    else:             set_all(0, 40, 0)
    time.sleep(0.08)