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Component list

  1. Raspberry Pi
  2. DHT11/22 or AM2302 temperature and humidity sensor
  3. 4.7K or 10K resister
  4. Breadboard
  5. Jumper wires

1. RPI and sensor Hardware preparation

First of all follow the tutorial on this url to prepare the RPI and sensor hardware.Temperature monitoring with Raspberry Pi and DHT11/22 temperature and humidity sensor

You only need to follow the steps from 1 to 4. Assuming that now we have the working scripts read_temperature.sh and read_humidity.sh you can follow the instructions given below.

2. GadgetKeeper configuration

Follow the Instructions in this url and implement the remote property. Implement Remote Property

Use 10000 like bigger value instead of 1000 as the timeout value in the step 2.

3. MQTT client preparation

  1. create a directory MQTT

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    sudo mkdir MQTT
                          cd MQTT/

  2. Download the mosquitto from this site or simply use the following command. http://mosquitto.org/download/

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    sudo wget http://mosquitto.org/files/source/mosquitto-1.0.2.tar.gz
  3. I used this mosquitto-1.0.2.tar.gz version for this tutorial

  4. Follow these commands to install mosquitto

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    sudo apt-get install libwrap0-dev
                          tar zxf mosquitto-1.0.2.tar.gz
                          cd mosquitto-1.0.2/
                          make
                          sudo make install
                          sudo ldconfig
                          sudo make clean
                          sudo iptables -A INPUT -p tcp -m tcp --dport 1883 -j ACCEPT

  5. If it fails the compile process try the following supportive commands on the terminal to install the dependency libraries. Then compile again

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    sudo apt-get install libssl-dev
                          sudo apt-get install python-mosquitto

  6. Next step is to prepare the MQTT client script to communicate with gadgetkeeper MQTT server. Following Python script can be used to do it. First go to the gadgetkeeper directory we created on the Temperature monitoring with Raspberry Pi and DHT11/22 temperature and humidity sensor tutorial. Then create a file as follows

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    cd /root/gadgetkeeper/
                          sudo nano mqtt_listner.py

    Then paste the following Python code on it.

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    #!/usr/bin/python
     
                          import time
                          import mosquitto
                          import random
                          import commands
     
                          ###############################################
     
                          # change this thing ID as required
                          THING_ID="c91d2bdbbf3911e3ab9651a372c40aa5"
                          BROKER_NAME="api.gadgetkeeper.com"
     
                          ###############################################
     
                          topic = 'thing.' + THING_ID
                          broker = BROKER_NAME
                          client_name = "device-1"
                          last_id = ""
     
                          def on_message(mosq, obj, msg):
                          global last_id
                          print 'Request: ' +  msg.payload
                          id,jsn,cmd = msg.payload.split(',', 2 );
                          #print id
                          #print jsn
                          #print cmd
                          if last_id == id:
                          print 'Update successful'
                          return
                          last_id = id
                          #data_val = 20.00
                          #data_val = random.uniform(1.5, 100.9) #genarate random value for testing
                          #read temperature from the sensor
                          shl_cmd = '/root/gadgetkeeper/read_temperature.sh'
                          #read humidity from the sensor
                          #shl_cmd = '/root/gadgetkeeper/read_humidity.sh'
                          data_val = commands.getoutput(shl_cmd)
                          if data_val:
                          print 'Sensor reading: ' + data_val
                          else:
                          time.sleep(2) #delay 2s and try again
                          data_val = commands.getoutput(shl_cmd)
                          if data_val:
                          print 'Sensor reading: ' + data_val
                          else:
                          data_val = -1000.0 # If sensor reading fails assign this value
                          print 'Sensor read error'
                          reply_msg = id + ',' + jsn + ',' + "\"result\":" + str(data_val) + '}'
                          print 'Response: ' + reply_msg
                          #client_rply = mosquitto.Mosquitto("device-1")
                          #client_rply.connect(broker)
                          #client_rply.publish(topic, reply_msg ,0)
     
                          reply_msg_new = reply_msg.replace('"', '\\"')
                          shl_cmd = '/usr/local/bin/mosquitto_pub  -h ' + broker + ' -p  1883 -t ' + topic + ' -m "' + reply_msg_new + '"'
                          #print shl_cmd
                          reply_prog = commands.getoutput(shl_cmd)
     
                          client = mosquitto.Mosquitto(client_name)
                          client.connect(broker)
                          client.subscribe(topic,0)
                          client.on_message = on_message
                          while True:
                          client.loop(15)
                          time.sleep(2)

  7. Now simply run this script as follows

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    sudo python mqtt_listner.py

                                                                                                                                                                                           

  8. Make sure that port 1883 is not blocked by the firewall.

4. Test the communication

Now you can use the "Get property value" step on the Implement Remote Property .Simply click on "Get" button and it should fetch the new value (Temperature or Humidity) from the RPI via the MQTT protocol.

Sensor read error will be shown as below (If the sensor is not available or fetching the temperature or humidity value from the sensor is failed, then the following response will be received from the MQTT client. You can assign any value for this as the error code on the python script. I have used -1000 to indicate error readings)

This window shows the communication between the client and server.

Following window shows a successful sensor reading upload to the server. Here the sensor value is 62.33

This window shows the communication between the client and server.

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