# Code based on a great tutorial by Matt from raspberrypi-spy.co.uk
# of how to use the MCP3008 IC chip with modifications by me, Bryce M
# for the specific type of weather sensors we are using
#DHT library from Adafruit for the temperature and humidity sensor
import spidev
import time
import os
import Adafruit_DHT
dht = Adafruit_DHT.AM2302
#Open SPI bus
spi = spidev.SpiDev()
spi.open(0,0)
# Function to read SPI data from MCP3008
# Channel must be an integer 0-7
def ReadChannel(channel):
adc = spi.xfer2([1,(8+channel)<<4,0])
data = ((adc[1]&3) << 8) + adc[2]
return data
def GetRainfall():
rainfall = ReadChannel(1)
rRef = ReadChannel(2)
# Calculates the resistance of the ETape water strip
# Vout = (R2 * Vin) / (R1+R2)
rainfall = (rainfall * 470) / (1023 – rainfall)
rRef = (rRef * 470) / (1023 – rRef)
return rainfall, rRef
def GetTempHumid():
humid, temp = Adafruit_DHT.read(dht, 22)
# If either reading returns null/none the value is assigned to be -1
if humid is None:
humid = -1
if temp is None:
temp = -1
# Returns humidity in percentage and temp in Celsius
return humid, temp
def GetWindSpeed():
speed = ReadChannel(0)
# Determine voltage
voltage = (speed * 3.3)/float(1023)
# Use voltage to determine speed
# voltage/meters per second ratio:
# 0.47V = 0 m/s — 2V = 32.4 m/s
speed = ((voltage – 0.47) * 16.2)
#Disregard voltage if not necessary
#Returns speed in meters per second
return round(speed, 2), round(voltage, 2)
def SpeedToMPH(speed):
“””Converts meters per second windspeed to miles per hour”””
# 1 mile = 1609.34 meters
speed = (speed * 3600) / 1609.3
return round(speed, 2)
def TempToFahrenheit(temp):
temp = ((temp * 9) / 5) + 32
return round(temp, 2)
def RainfallToInches(rainfall, rRef):
rainfall = (rainfall – previous) / float(150)
rainfall = round(rainfall, 2)
return rainfall
def RainfallToCentimeters(rainfall, rRef):
rainfall = (rainfall – previous) / float(60)
rainfall = round(rainfall, 2)
return rainfall
delay = 6
while True:
#Read in data
humid, temp = GetTempHumid()
speed, voltage = GetWindSpeed()
rainfall, rRef = GetRainfall()
#Example print
print “———————-”
print(“Speed: {} ({}V)”.format(speed,voltage))
print(“Temp: {} Humidity {}”.format(round(temp, 2), round(humid, 2)))
print(“Rainfall {} – {}”.format(rainfall, rRef))
time.sleep(delay)
