def read_distance():
    """Reads distance from HC-SR04."""
    # Send trigger pulse
    try:
        trigger.off()
        sleep(0.000002)  # Ensure it's low
        trigger.on()
        sleep(0.00002)   # 20 microsecond pulse
        trigger.off()

        print("[DEBUG] Trigger pulse sent")

        # Measure echo pulse
        pulse_duration = time_pulse_us(echo, 1, 23529)  # Timeout for 400 cm range
        print(f"[DEBUG] Pulse duration (us): {pulse_duration}")

        if pulse_duration < 0 or pulse_duration > 23529:  # Invalid duration
            print("[ERROR] Pulse duration out of range or timeout")
            return None

        # Calculate distance
        distance = (pulse_duration * 0.0343) / 2  # Convert to cm
        return round(distance, 2)
    except Exception as e:
        print("[ERROR] Exception occurred:", str(e))
        return None