gistfile1.txt

#include <Servo.h>

static const uint8_t SERVO_PIN = 9;
static const uint8_t TRIG_PIN  = 10;
static const uint8_t ECHO_PIN  = 11;

Servo s;

long readDistanceCm() {
  // Trigger pulse
  digitalWrite(TRIG_PIN, LOW);
  delayMicroseconds(2);
  digitalWrite(TRIG_PIN, HIGH);
  delayMicroseconds(10);
  digitalWrite(TRIG_PIN, LOW);

  // Echo pulse width (timeout ~ 25 ms => ~4m max)
  unsigned long us = pulseIn(ECHO_PIN, HIGH, 25000UL);
  if (us == 0) return -1; // timeout / no echo

  // Sound speed: 343 m/s => 29.1 us per cm round-trip is 58.2 us per cm
  long cm = (long)(us / 58UL);
  return cm;
}

void setup() {
  Serial.begin(115200);

  pinMode(TRIG_PIN, OUTPUT);
  pinMode(ECHO_PIN, INPUT);

  s.attach(SERVO_PIN);
  s.write(90);
  delay(400);
}

void loop() {
  // sweep 20 -> 160
  for (int angle = 20; angle <= 160; angle += 10) {
    s.write(angle);
    delay(180); // give servo time to move

    long cm = readDistanceCm();
    Serial.print("angle=");
    Serial.print(angle);
    Serial.print(" cm=");
    Serial.println(cm);

    delay(60);
  }

  // sweep back 160 -> 20
  for (int angle = 160; angle >= 20; angle -= 10) {
    s.write(angle);
    delay(180);

    long cm = readDistanceCm();
    Serial.print("angle=");
    Serial.print(angle);
    Serial.print(" cm=");
    Serial.println(cm);

    delay(60);
  }
}