"""
IR sensor: helps the robot stay on the path (like a black line).
Ultrasonic sensor: detects obstacles in front and stops or turns the robot.
Together: the robot follows the path safely without crashing into anything.
"""

from machine import Pin, time_pulse_us
from time import sleep

# --- Ultrasonic Pins ---
trigger = Pin(3, Pin.OUT)
echo = Pin(2, Pin.IN)

# --- IR Sensor Pin ---
ir_sensor = Pin(15, Pin.IN)

SOUND_SPEED = 0.0343  # cm/us

def read_distance():
    trigger.low()
    sleep(0.002)
    trigger.high()
    sleep(0.01)
    trigger.low()
    duration = time_pulse_us(echo, 1, 30000)  
    distance = (duration * SOUND_SPEED) / 2
    return distance

while True:
    dist = read_distance()
    ir_state = ir_sensor.value()  
    
    print("Distance: {:.2f} cm | IR Sensor: {}".format(dist, ir_state))
    
    if dist < 20:
        print("⚠️ Obstacle too close!")
    
    if ir_state == 0:
        print("⚠️ Line detected!")
    
    sleep(0.5)