from machine import Pin, time_pulse_us
from time import sleep, sleep_ms, sleep_us
  

# Ultrasonic Sensor Pins
TRIG = Pin(15, Pin.OUT)
ECHO = Pin(14, Pin.IN)

# CSV file name
log_file = "/distance_log.csv"

# Create CSV file and add header if it doesn't exist
with open(log_file, "a") as f:
    f.seek(0, 0)
    if not f.read(1):
        f.write("Sr No.,Distance (cm)\n")

# Function to measure distance
def get_distance():
    TRIG.low()
    sleep_ms(2)

    TRIG.high()
    sleep_us(10)
    TRIG.low()

    duration = time_pulse_us(ECHO, 1, 30000)

    # If no echo is received
    if duration < 0:
        return -1

    # Convert time to distance in cm
    distance = (duration * 0.0343) / 2

    return round(distance, 2)

# Serial number
sr_no = 1

# Main loop
while True:

    distance = get_distance()

    # Save to CSV file
    with open(log_file, "a") as f:
        f.write(str(sr_no) + "," + str(distance) + "\n")

    # Display on Serial Monitor
    print("Reading", sr_no, ": Distance =", distance, "cm")

    sr_no += 1

    # Wait 0.5 seconds before next reading
    sleep(0.5)