Code now shows temperature and humidity infinitely until keyboard interrupt.

DHT11_Python/LICENSE.md

@@ -0,0 +1,21 @@
+MIT License
+
+Copyright (c) 2016 Zoltan Szarvas
+
+Permission is hereby granted, free of charge, to any person obtaining a copy
+of this software and associated documentation files (the "Software"), to deal
+in the Software without restriction, including without limitation the rights
+to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all
+copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+SOFTWARE.

DHT11_Python/README.md

@@ -0,0 +1,44 @@
+# DHT11 Python library
+
+This simple class can be used for reading temperature and humidity values from DHT11 sensor on Raspberry Pi.
+
+# Installation
+
+To install, just run following:
+
+```
+pip install dht11
+```
+
+# Usage
+
+1. Instantiate the `DHT11` class with the pin number as constructor parameter.
+2. Call `read()` method, which will return `DHT11Result` object with actual values and error code.
+
+For example:
+
+```python
+import RPi.GPIO as GPIO
+import dht11
+
+# initialize GPIO
+GPIO.setwarnings(False)
+GPIO.setmode(GPIO.BCM)
+GPIO.cleanup()
+
+# read data using pin 14
+instance = dht11.DHT11(pin = 14)
+result = instance.read()
+
+if result.is_valid():
+    print("Temperature: %-3.1f C" % result.temperature)
+    print("Humidity: %-3.1f %%" % result.humidity)
+else:
+    print("Error: %d" % result.error_code)
+```
+
+For working example, see `dht11_example.py` (you probably need to adjust pin for your configuration)
+
+# License
+
+This project is licensed under the terms of the MIT license.

DHT11_Python/dht11/__init__.py

@@ -0,0 +1,203 @@
+import time
+import RPi
+
+
+class DHT11Result:
+    'DHT11 sensor result returned by DHT11.read() method'
+
+    ERR_NO_ERROR = 0
+    ERR_MISSING_DATA = 1
+    ERR_CRC = 2
+
+    error_code = ERR_NO_ERROR
+    temperature = -1
+    humidity = -1
+
+    def __init__(self, error_code, temperature, humidity):
+        self.error_code = error_code
+        self.temperature = temperature
+        self.humidity = humidity
+
+    def is_valid(self):
+        return self.error_code == DHT11Result.ERR_NO_ERROR
+
+
+class DHT11:
+    'DHT11 sensor reader class for Raspberry'
+
+    __pin = 0
+
+    def __init__(self, pin):
+        self.__pin = pin
+
+    def read(self):
+        RPi.GPIO.setup(self.__pin, RPi.GPIO.OUT)
+
+        # send initial high
+        self.__send_and_sleep(RPi.GPIO.HIGH, 0.05)
+
+        # pull down to low
+        self.__send_and_sleep(RPi.GPIO.LOW, 0.02)
+
+        # change to input using pull up
+        RPi.GPIO.setup(self.__pin, RPi.GPIO.IN, RPi.GPIO.PUD_UP)
+
+        # collect data into an array
+        data = self.__collect_input()
+
+        # parse lengths of all data pull up periods
+        pull_up_lengths = self.__parse_data_pull_up_lengths(data)
+
+        # if bit count mismatch, return error (4 byte data + 1 byte checksum)
+        if len(pull_up_lengths) != 40:
+            return DHT11Result(DHT11Result.ERR_MISSING_DATA, 0, 0)
+
+        # calculate bits from lengths of the pull up periods
+        bits = self.__calculate_bits(pull_up_lengths)
+
+        # we have the bits, calculate bytes
+        the_bytes = self.__bits_to_bytes(bits)
+
+        # calculate checksum and check
+        checksum = self.__calculate_checksum(the_bytes)
+        if the_bytes[4] != checksum:
+            return DHT11Result(DHT11Result.ERR_CRC, 0, 0)
+
+        # ok, we have valid data
+
+        # The meaning of the return sensor values
+        # the_bytes[0]: humidity int
+        # the_bytes[1]: humidity decimal
+        # the_bytes[2]: temperature int
+        # the_bytes[3]: temperature decimal
+
+        temperature = the_bytes[2] + float(the_bytes[3]) / 10
+        humidity = the_bytes[0] + float(the_bytes[1]) / 10
+
+        return DHT11Result(DHT11Result.ERR_NO_ERROR, temperature, humidity)
+
+    def __send_and_sleep(self, output, sleep):
+        RPi.GPIO.output(self.__pin, output)
+        time.sleep(sleep)
+
+    def __collect_input(self):
+        # collect the data while unchanged found
+        unchanged_count = 0
+
+        # this is used to determine where is the end of the data
+        max_unchanged_count = 100
+
+        last = -1
+        data = []
+        while True:
+            current = RPi.GPIO.input(self.__pin)
+            data.append(current)
+            if last != current:
+                unchanged_count = 0
+                last = current
+            else:
+                unchanged_count += 1
+                if unchanged_count > max_unchanged_count:
+                    break
+
+        return data
+
+    def __parse_data_pull_up_lengths(self, data):
+        STATE_INIT_PULL_DOWN = 1
+        STATE_INIT_PULL_UP = 2
+        STATE_DATA_FIRST_PULL_DOWN = 3
+        STATE_DATA_PULL_UP = 4
+        STATE_DATA_PULL_DOWN = 5
+
+        state = STATE_INIT_PULL_DOWN
+
+        lengths = [] # will contain the lengths of data pull up periods
+        current_length = 0 # will contain the length of the previous period
+
+        for i in range(len(data)):
+
+            current = data[i]
+            current_length += 1
+
+            if state == STATE_INIT_PULL_DOWN:
+                if current == RPi.GPIO.LOW:
+                    # ok, we got the initial pull down
+                    state = STATE_INIT_PULL_UP
+                    continue
+                else:
+                    continue
+            if state == STATE_INIT_PULL_UP:
+                if current == RPi.GPIO.HIGH:
+                    # ok, we got the initial pull up
+                    state = STATE_DATA_FIRST_PULL_DOWN
+                    continue
+                else:
+                    continue
+            if state == STATE_DATA_FIRST_PULL_DOWN:
+                if current == RPi.GPIO.LOW:
+                    # we have the initial pull down, the next will be the data pull up
+                    state = STATE_DATA_PULL_UP
+                    continue
+                else:
+                    continue
+            if state == STATE_DATA_PULL_UP:
+                if current == RPi.GPIO.HIGH:
+                    # data pulled up, the length of this pull up will determine whether it is 0 or 1
+                    current_length = 0
+                    state = STATE_DATA_PULL_DOWN
+                    continue
+                else:
+                    continue
+            if state == STATE_DATA_PULL_DOWN:
+                if current == RPi.GPIO.LOW:
+                    # pulled down, we store the length of the previous pull up period
+                    lengths.append(current_length)
+                    state = STATE_DATA_PULL_UP
+                    continue
+                else:
+                    continue
+
+        return lengths
+
+    def __calculate_bits(self, pull_up_lengths):
+        # find shortest and longest period
+        shortest_pull_up = 1000
+        longest_pull_up = 0
+
+        for i in range(0, len(pull_up_lengths)):
+            length = pull_up_lengths[i]
+            if length < shortest_pull_up:
+                shortest_pull_up = length
+            if length > longest_pull_up:
+                longest_pull_up = length
+
+        # use the halfway to determine whether the period it is long or short
+        halfway = shortest_pull_up + (longest_pull_up - shortest_pull_up) / 2
+        bits = []
+
+        for i in range(0, len(pull_up_lengths)):
+            bit = False
+            if pull_up_lengths[i] > halfway:
+                bit = True
+            bits.append(bit)
+
+        return bits
+
+    def __bits_to_bytes(self, bits):
+        the_bytes = []
+        byte = 0
+
+        for i in range(0, len(bits)):
+            byte = byte << 1
+            if (bits[i]):
+                byte = byte | 1
+            else:
+                byte = byte | 0
+            if ((i + 1) % 8 == 0):
+                the_bytes.append(byte)
+                byte = 0
+
+        return the_bytes
+
+    def __calculate_checksum(self, the_bytes):
+        return the_bytes[0] + the_bytes[1] + the_bytes[2] + the_bytes[3] & 255

DHT11_Python/example.py

@@ -0,0 +1,26 @@
+import RPi.GPIO as GPIO
+import dht11
+import time
+import datetime
+
+# initialize GPIO
+GPIO.setwarnings(True)
+GPIO.setmode(GPIO.BCM)
+
+# read data using pin 14
+instance = dht11.DHT11(pin=14)
+
+try:
+	while True:
+	    result = instance.read()
+	    if result.is_valid():
+	        print("Last valid input: " + str(datetime.datetime.now()))
+
+	        print("Temperature: %-3.1f C" % result.temperature)
+	        print("Humidity: %-3.1f %%" % result.humidity)
+
+	    time.sleep(6)
+
+except KeyboardInterrupt:
+    print("Cleanup")
+    GPIO.cleanup()

DHT11_Python/setup.py

@@ -0,0 +1,23 @@
+from setuptools import setup, find_packages
+
+with open("README.md", "r") as fh:
+    long_description = fh.read()
+
+setup(
+    name="dht11",
+    version="0.1.0",
+    author="Zoltán Szarvas",
+    author_email="",
+    description="Pure Python library for reading DHT11 sensor on Raspberry Pi",
+    long_description=long_description,
+    long_description_content_type="text/markdown",
+    url="https://github.com/szazo/DHT11_Python",
+    packages=find_packages(),
+    install_requires=["RPi.GPIO"],
+    classifiers=[
+        "Programming Language :: Python :: 3",
+        "License :: OSI Approved :: MIT License",
+        "Operating System :: OS Independent",
+    ],
+    python_requires='>=3.6',
+)

setup.sh

@@ -56,6 +56,7 @@ if [ ! -d "$PROJECT_DIR" ]; then
   echo -e "$line\nCreating 'dht11-sensor' in Desktop directory for current user.\n$line\n"
   mkdir -p "$PROJECT_DIR"
   cp "./temp-calc.py" "$PROJECT_DIR/"
+  cp -r "./DHT11_Python/" "$PROJECT_DIR/DHT11_Python"
   echo -e "$line\nCreated '$PROJECT_DIR' directory.\n$line\n"
 else
   echo -e "$line\n$PROJECT_DIR already exists. Please delete the folder before running this script.\n$line\n\nExiting..."
@@ -71,6 +72,12 @@ echo -e "$line\nActivating virtual environment...\n$line\n"
 source $PROJECT_DIR/bin/activate
 
 echo -e "$line\nInstalling dependencies...\n$line\n"
-pip3 install --upgrade RPi.GPIO setuptools dht11
+pip install --upgrade RPi.GPIO setuptools
+# Alternatively, instead of executing the next four lines, you can also run "pip install dht11"
+# but I've decided to keep the files for "dht11" package locally available for installation in the script.
+cd "$PROJECT_DIR/DHT11_Python"
+pip install .
+pip show dht11
+cd "$PROJECT_DIR/"
 
 echo -e "\n\n\n$line$line$line\nSetup completed.\nExecute the command 'python3 temp-calc.py' to calculate the temperature.\n# DESIGNED AND ENGINEERED BY KSHITIJ.\n# END OF SCRIPT\n$line$line$line\n\n\n"

temp-calc.py

@@ -2,12 +2,15 @@
 
 import RPi.GPIO as GPIO
 import dht11
+import time
 
 # initialize GPIO
 GPIO.setwarnings(False)
 GPIO.setmode(GPIO.BCM)
 GPIO.cleanup()
 
+try:
+  while True:
     # read data using pin 16
     instance = dht11.DHT11(pin = 16)
     result = instance.read()
@@ -17,5 +20,7 @@ if result.is_valid():
       print("Humidity: %-3.1f %%" % result.humidity)
     else:
       print("Error: %d" % result.error_code)
-
+    time.sleep(3)
+except KeyboardInterrupt:
+  print("Program stopped by user.")
   GPIO.cleanup()