Documentation

// JSN-SR04T Waterproof Ultrasonic - Arduino Example
// Trig->D9, Echo->D10, 5V, GND

const int trigPin = 9;
const int echoPin = 10;

long readOnceCm() {
  digitalWrite(trigPin, LOW);  delayMicroseconds(4);
  digitalWrite(trigPin, HIGH); delayMicroseconds(10);
  digitalWrite(trigPin, LOW);
  long us = pulseIn(echoPin, HIGH, 40000UL);   // 40 ms timeout
  return us == 0 ? -1 : us / 58;
}

long readMedianCm() {
  long a = readOnceCm(); delay(60);
  long b = readOnceCm(); delay(60);
  long c = readOnceCm();
  // median of three
  if ((a >= b) == (a <= c)) return a;
  if ((b >= a) == (b <= c)) return b;
  return c;
}

void setup() {
  Serial.begin(115200);
  pinMode(trigPin, OUTPUT);
  pinMode(echoPin, INPUT);
  Serial.println("JSN-SR04T ready (blind zone < ~25 cm)");
}

void loop() {
  long cm = readMedianCm();
  if (cm < 0)        Serial.println("Out of range / no echo");
  else if (cm < 25)  Serial.println("Too close (blind zone)");
  else {
    Serial.print("Distance: ");
    Serial.print(cm);
    Serial.println(" cm");
  }
  delay(300);
}

# JSN-SR04T - ESP32 MicroPython Example
# Trig->GPIO 5, Echo->GPIO 18 (via 1k/2k divider), 5V->VIN

from machine import Pin, time_pulse_us
import time

trig = Pin(5, Pin.OUT, value=0)
echo = Pin(18, Pin.IN)

def read_once_cm():
    trig.value(0); time.sleep_us(4)
    trig.value(1); time.sleep_us(10)
    trig.value(0)
    us = time_pulse_us(echo, 1, 40000)   # 40 ms timeout
    return -1 if us < 0 else us // 58

def read_median_cm():
    vals = []
    for _ in range(3):
        vals.append(read_once_cm())
        time.sleep_ms(60)
    return sorted(vals)[1]

print("JSN-SR04T ready (blind zone < ~25 cm)")
while True:
    cm = read_median_cm()
    if cm < 0:
        print("Out of range / no echo")
    elif cm < 25:
        print("Too close (blind zone)")
    else:
        print("Distance: {} cm".format(cm))
    time.sleep(0.3)

#!/usr/bin/env python3
# JSN-SR04T - Raspberry Pi Example
# Trig->GPIO23, Echo->GPIO24 (via 1k/2k divider)

import RPi.GPIO as GPIO
import time, statistics

TRIG, ECHO = 23, 24
GPIO.setmode(GPIO.BCM)
GPIO.setup(TRIG, GPIO.OUT, initial=0)
GPIO.setup(ECHO, GPIO.IN)

def read_once_cm():
    GPIO.output(TRIG, 1); time.sleep(0.00001)
    GPIO.output(TRIG, 0)
    t0 = time.time()
    while GPIO.input(ECHO) == 0:
        if time.time() - t0 > 0.04: return -1
    start = time.time()
    while GPIO.input(ECHO) == 1:
        if time.time() - start > 0.04: return -1
    return (time.time() - start) * 17150

try:
    print("JSN-SR04T ready (blind zone < ~25 cm)")
    while True:
        vals = []
        for _ in range(3):
            d = read_once_cm()
            if d > 0: vals.append(d)
            time.sleep(0.06)
        if not vals:
            print("Out of range / no echo")
        else:
            cm = statistics.median(vals)
            if cm < 25: print("Too close (blind zone)")
            else:       print(f"Distance: {cm:.1f} cm")
        time.sleep(0.3)
except KeyboardInterrupt:
    GPIO.cleanup()
    print("Stopped by user")

# JSN-SR04T - Pico MicroPython Example (water tank level demo)
# Trig->GP3, Echo->GP2 (via 1k/2k divider), 5V->VBUS

from machine import Pin, time_pulse_us
import time

trig = Pin(3, Pin.OUT, value=0)
echo = Pin(2, Pin.IN)

TANK_DEPTH_CM = 120         # sensor face to tank bottom
SENSOR_OFFSET = 25          # keep sensor above max water by blind zone

def read_cm():
    trig.value(1); time.sleep_us(10); trig.value(0)
    us = time_pulse_us(echo, 1, 40000)
    return -1 if us < 0 else us // 58

while True:
    cm = read_cm()
    if cm < 0:
        print("No echo")
    else:
        water = TANK_DEPTH_CM - cm
        pct = max(0, min(100, water * 100 // (TANK_DEPTH_CM - SENSOR_OFFSET)))
        print("Air gap: {} cm | Water: {} cm | Tank: {}%".format(cm, water, pct))
    time.sleep(1)