How to use MQTT

Connect your device to mqtt.cheerlights.com:1883 and subscribe to the “cheerlights” topic. When the CheerLights color changes, the color name will be streamed to your device. You no longer have to poll for the latest CheerLights color on the ThingSpeak API.

Here are the valid color names:

• red (#FF0000)
• green (#008000)
• blue (#0000FF)
• cyan (#00FFFF)
• white (#FFFFFF)
• oldlace / warmwhite (#FDF5E6)
• purple (#800080)
• magenta (#FF00FF)
• yellow (#FFFF00)
• orange (#FFA500)
• pink (#FFC0CB)

Check out the CheerLights API documentation for more detail.

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CheerLights Introduction

Here’s a quick introduction to the CheerLights project for those who are new to the project. Imagine 1000’s of multicolored lights all around the world synchronized to one color. When one of the lights turns red, they all turn red. To control CheerLights, send a tweet to @cheerlights or include “cheerlights” somewhere in your message with the name of a color. This will cause a chain reaction and all of the CheerLights displays and apps will change their color to red.

ThingSpeak MQTT Service

CheersLights is powered by ThingSpeak IoT. And, this year, I am happy to introduce real-time CheerLights updates using ThingSpeak’s new MQTT service. Using the MQTT service by ThingSpeak, your CheerLights change instantly. ThingSpeak has posted an example that gets a Particle Photon connected to CheerLights using MQTT. The Subscribe to Channel Updates Using Particle Photon Client example shows you how to use a Particle Photon Wi-Fi board to subscribe to channel updates from the CheerLights channel. The program displays the color read from the channel on the built-in LED on the Photon board. You can subscribe to the channel feed or directly to the color field on the CheerLights channel.

Once you learn how to use the MQTT service from ThingSpeak, you can easily adapt it to your IoT project. This is a great way to have real-time control of a device or real-time monitoring of sensors.

If you want to follow the project and see what others are building, visit CheerLights.com or follow on Twitter.

Setup ThingSpeak

• Sign up for ThingSpeak (or log in if you have an account)
• Create a new channel
• Note the Channel ID and Write API Key

Setup MQTT.fx

• Download and install MQTT.fx.
• Configure the connection profile for the desktop MQTT client.
  • Broker Address: mqtt.thingspeak.com
  • Broker Port: 1883

• Click Connect to connect to the ThingSpeak MQTT broker.

• Enter the topic channels/<channelID>/publish/<apikey> to publish data to a channel feed. Replace <channelID> with the channel ID and <apikey> with the write API key of the channel. Enter the message to publish to the channel feed. This PUBLISH message publishes a value of 45 to field 1 and 60 to field 2 of the specified channel, along with a status message MQTTPUBLISH.

• Alternatively, you can enter the topic channels/<channelID>/publish/fields/field<fieldnumber>/<apikey> to publish to a channel field. Replace <channelID> with the channel ID, <fieldnumber> with field number that want to update, and <apikey> with the write API key of the channel. Enter the message to publish to the channel field. This PUBLISH message publishes a value of 45 to field 1 of the specified channel.

Additional Resources

• MQTT Basics – Learn about the publish/subscribe architecture for connecting bandwidth and power-constrained devices over wireless networks
• MQTT Client Configuration – Learn how to set up an MQTT client to communicate with the ThingSpeak MQTT broker
• Choose Between REST and MQTT – Learn when to use REST and MQTT to update a channel

MQTT operates under a publish/subscribe model in which clients connect to the MQTT broker and either publish data or subscribe to topics to receive data from other clients.  MQTT messages can be sent using unsecured TCP, which is the easiest and has the lower RAM, CPU, and bandwidth requirements.  MQTT messages can also be sent using WebSockets.  This may be needed for situations when the standard port for MQTT, 1883, is blocked on the network.  When using MQTT over WebSockets, it is possible to encrypt the communication with SSL.  If your hardware is capable of using SSL over a WebSocket, that is the recommended method.

On the Raspberry Pi, an MQTT client library is required to send data to ThingSpeak.  Paho is an open-source MQTT client library that will be used for this example.  It has been adapted to many languages, including Python.

This example will demonstrate how to publish data to a ThingSpeak channel using the Paho library.  The CPU and RAM usage of the Raspberry Pi will be measured and published to ThingSpeak every 20 seconds.

Setup

1) Create a new channel as shown in Collect Data in a New Channel with two fields named “CPU (%)” and “RAM (%)”.

2) Create an MQTT device by clicking Devices > MQTT at the top of the ThingSpeak page, then Add Device. When setting up the device and adding the new channel to its authorized list, click Download Credentials > Plain Text. For details, see Create a ThingSpeak MQTT Device. Use the saved credentials in the Code section below.

3) Download the Paho MQTT client library for Python. You can use the command line to install the libraries. If you are using Python 2, use this code:

sudo pip install paho-mqtt
sudo pip install psutil

If you use Python 3, use this code:

sudo pip3 install paho-mqtt
sudo pip3 install psutil

Publishing to ThingSpeak Example

This example shows how simple it can be to send data to ThingSpeak using MQTT.

Three MQTT connection methods are demonstrated in this example: TCP, WebSockets, and SSL. To use a conventional TCP socket on port 1883, set useUnsecuredTCP=True.  This connection method is the simplest and requires the least system resources.  To use WebSockets on port 80, set useUnsecuredWebsockets=True.  Websockets are helpful when the default MQTT port is blocked on the local network.  Finally, if encryption is required, set useSSLWebsockets=True.   Be sure only to set one of the connection method variables to True and leave the other two False.

Also, be sure to change the channel ID and API key to your channel’s settings.

# Publich to a ThingSpeak Channel Using MQTT
# 
# This is an example of publishing to multiple fields simultaneously.
# Connections over standard TCP, websocket or SSL are possible by setting
# the parameters below.
#
# CPU and RAM usage is collected every 20 seconds and published to a
# ThingSpeak channel using an MQTT Publish
#
# This example requires the Paho MQTT client package which
# is available at: http://eclipse.org/paho/clients/python
import paho.mqtt.publish as publish
import psutil
import string

# The ThingSpeak Channel ID.
# Replace <YOUR-CHANNEL-ID> with your channel ID.
channel_ID = "<YOUR-CHANNEL-ID>"

# The hostname of the ThingSpeak MQTT broker.
mqtt_host = "mqtt3.thingspeak.com"

# Your MQTT credentials for the device
mqtt_client_ID = "<YOUR-CLIENT-ID>"
mqtt_username  = "<YOUR-USERNAME>"
mqtt_password  = "<YOUR-MQTT-PASSWORD>"

t_transport = "websockets"
t_port = 80

# Create the topic string.
topic = "channels/" + channel_ID + "/publish"

while (True):

    # get the system performance data over 20 seconds.
    cpu_percent = psutil.cpu_percent(interval=20)
    ram_percent = psutil.virtual_memory().percent

    # build the payload string.
    payload = "field1=" + str(cpu_percent) + "&field2=" + str(ram_percent)

    # attempt to publish this data to the topic.
    try:
        print ("Writing Payload = ", payload," to host: ", mqtt_host, " clientID= ", mqtt_client_ID, " User ", mqtt_username, " PWD ", mqtt_password)
        publish.single(topic, payload, hostname=mqtt_host, transport=t_transport, port=t_port, client_id=mqtt_client_ID, auth={'username':mqtt_username,'password':mqtt_password})
    except (keyboardInterrupt)
        break
    except Exception as e:
        print (e) 

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