readings.py

#!/usr/bin/python
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#
# ultrasonic_1.py
# Measure distance using an ultrasonic module
#
# Author : Matt Hawkins
# Date   : 09/01/2013

# Import required Python libraries
import time
import RPi.GPIO as GPIO

# Imports for Google Sheet
import json
import gspread
from oauth2client.service_account import ServiceAccountCredentials
import datetime

# Use BCM GPIO references
# instead of physical pin numbers
GPIO.setmode(GPIO.BCM)

# Define GPIO to use on Pi
GPIO_TRIGGER = 11
GPIO_ECHO = 9

# You need to change the variable "compensation" according to the distance from the edge of the pit to the sensor
compensation = -11

print "Ultrasonic Measurement"

# Set pins as output and input
GPIO.setup(GPIO_TRIGGER,GPIO.OUT)  # Trigger
GPIO.setup(GPIO_ECHO,GPIO.IN)      # Echo

# Set trigger to False (Low)
GPIO.output(GPIO_TRIGGER, False)

# Allow module to settle
time.sleep(0.5)

# Send 10us pulse to trigger
GPIO.output(GPIO_TRIGGER, True)
time.sleep(0.00001)
GPIO.output(GPIO_TRIGGER, False)
start = time.time()
while GPIO.input(GPIO_ECHO)==0:
  start = time.time()

while GPIO.input(GPIO_ECHO)==1:
  stop = time.time()

# Calculate pulse length
elapsed = stop-start

# Distance pulse travelled in that time is time
# multiplied by the speed of sound (cm/s)
distance = elapsed * 34000

# That was the distance there and back so halve the value
distance = distance / 2
distance = distance + compensation

print "Distance : %.1f" % distance

# Reset GPIO settings
GPIO.cleanup()


# Upload info to Google Sheet
scope = ['https://spreadsheets.google.com/feeds']
credentials = ServiceAccountCredentials.from_json_keyfile_name('creds9.json', scope)

gc = gspread.authorize(credentials)
wks = gc.open("Readings")
wksheet = wks.worksheet("Last")

now = datetime.datetime.now()

d = wksheet.cell(1,1)
d.value = now
v = wksheet.cell(1,2)
v.value = distance

#wksheet.update_cells([d,v])