# PIR Motion Detection with Raspberry Pi
# COMP-556 Assignment 1 - Response Time Comparison
# Modified to match Arduino code functionality and measure response time

import RPi.GPIO as GPIO
import time

# Pin configuration - Using consistent pin numbering
LED_PIN = 18      # GPIO 18 for LED
PIR_PIN = 17      # GPIO 17 for PIR sensor

# Setup GPIO
GPIO.setmode(GPIO.BCM)
GPIO.setup(PIR_PIN, GPIO.IN)
GPIO.setup(LED_PIN, GPIO.OUT)

print("Raspberry Pi PIR Motion Detection - Response Time Test")

# Initialize state variables
state = False  # Equivalent to LOW in Arduino

try:
    while True:
        start_time = time.time()  # Start timing measurement
        
        pir_value = GPIO.input(PIR_PIN)  # Read PIR sensor
        
        if pir_value == GPIO.HIGH:       # Motion detected
            GPIO.output(LED_PIN, GPIO.HIGH)  # Turn LED ON
            response_time = (time.time() - start_time) * 1000000  # Convert to microseconds
            
            if not state:  # If state was LOW
                print(f"Motion detected! Response Time: {response_time:.2f} μs")
                state = True  # Update state to HIGH
                
        else:  # No motion detected
            GPIO.output(LED_PIN, GPIO.LOW)  # Turn LED OFF
            if state:  # If state was HIGH
                print("Motion stopped!")
                state = False  # Update state to LOW
        
        time.sleep(0.5)  # Delay between readings (500ms like Arduino)

except KeyboardInterrupt:
    print("Program stopped by user")
    GPIO.cleanup()  # Clean up GPIO