Adafruit_MQTT_Library/examples/mqtt_arbitrary_data

Adafruit MQTT Library Arbitrary Data Publish Example

This example illustrates publishing an arbitrary data packet using the Adafruit MQTT library to an MQTT feed which can then be parsed by the included python subscriber client. Possible usage cases include adding metadata (collection time, sensor info etc) to a datapoint.

My motivation for this was wanting to be able to include metadata to a post. Specifically, I was playing around with a Teviso RD3024 radiation sensor, and a salvaged Americium radiation source from a smoke detector, at varying distances from the sensor. I wanted a way to associate the collection time, and distance between the source and sensor with the actual radiation reading itself.

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Installing and configuring Mosquitto broker (minimal working setup):

####Installing on Raspberry Pi/Linux:

sudo apt-get install mosquitto
cd /etc/mosquitto/
#See "Configuring Mosquitto Broker below"

####Installing On a Mac:

brew install mosquitto
cd /usr/local/etc/mosquitto
#See "Configuring Mosquitto Broker below"

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####Configuring Mosquitto broker

sudo nano mosquitto.conf

Now we have to enable a password file to correctly interface with the Adafruit MQTT library. Scroll about two thirds of the way down until you see:

# -----------------------------------------------------------------
# Default authentication and topic access control
# -----------------------------------------------------------------

You should see #password_file about a paragraph after that. Change

#password_file

To

password_file pwfile

Now ctrl-x to save and exit.

You're almost done! We just have to create and populate the password file we just configured. The default user info is:

• Arduino Subscriber:

  • Username: TestUser
  • Password: TestUser

• Python Subscriber:

  • Username: TestPy
  • Password: TestPy

touch pwfile #create the password file
mosquitto_passwd pwfile TestUser #Enter and confirm password when prompted
mosquitto_passwd pwfile TestPy #Enter and confirm password when prompted

####Running Mosquitto broker Now run Mosquitto broker to allow Arduino publisher and Python subscriber to communicate

mosquitto

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Using Example Python Subscriber:

####Installing Python subscriber Install dependencies if you haven't already

cd ../Adafruit_MQTT_Library/examples/mqtt_arbitrary_buffer/python_subscriber
pip install -r requirements.txt

####Installing Python subscriber Run python script with default values and watch your parsed data print out.

python subscriber.py #Add -h flag to see modifiable options

Assuming that the Mosquitto broker is running in the background and the Adafruit_MQTT client (Arduino) is publishing, you should see the example data print out every 10 seconds.

MQTT:  Connection successful
Connection successful
Subscribed to /feeds/arb_packet
Received char Array: "Hello!", val1: -4533, val2: 73102, val3: 3354...
Received char Array: "Hello!", val1: -4533, val2: 83611, val3: 3354...
Received char Array: "Hello!", val1: -4533, val2: 94115, val3: 3354...