Creating the Automation

The first thing we need to do is create an Automation that will pass data from Home Assistant to our MQTT topics whenever that information is updated. To do this you will want to open the main menu on the left side of the Home Assistant screen.

The Trigger

Now that we have our Automation created, we need to tell it when this automation should be executed. This is called the Trigger and there are many ways we can set it up. For this example we will set our automation to trigger whenever the weather report from Home Assistant changes its State.

The From, To, and For options are useful if you want this to trigger only if the weather changes from sunny to rainy, but we want this to trigger whenever there is any change to this entity. So we will leave these blank and any change to the weather.home entities state will result in this automation running.

You can add as many triggers as you want and if any of them are true, then the automation will run.

Conditions are similar to Triggers but are not required. If you set any Conditions, all of them need to be True for the Automation to be executed. An example of how this could be used would be to make it so that this automation only ran if someone was home and the sun is up.

Actions

Now we get to the fun part, were we tell the automation what to do once triggered. You can have this do as many things as you like, but for this example we will simply format a message for MQTT that contains the current weather and temperature. This process uses Data Templates from Home Assistant so that we can get additional data attributes from the weather.home entity.

topic: pyportal/feed1
payload_template: >- 
  {{ states('weather.home') }} and {{ state_attr('weather.home', 'temperature') }}°
retain: true
qos: 2

topic: pyportal/feed1
payload_template: >- 
  {{ states('weather.home') }} and {{ state_attr('weather.home', 'temperature') }}°
retain: true
qos: 2

• Topic: The MQTT topic that you want to publish to.
• Retain: Is this message flagged to be retained.
• QOS: Quality of Service for this message. QOS of 2 ensures that the message is delivered no more or less than one time.
• Payload Template: This allows you to pull data from the Home Assistant local API and format it into a message string. 
  
  • {{ states('entity_id') }} - prints the current State of the stated Entity.
  • {{ state_attr('entity_id', 'entity_attribute') }} - prints the value of a particular attribute from a stated Entity.

Now you should be able to click the Save icon at the bottom right of the screen.

You will want to create another one of these for pyportal/feed2 and any other data that does not already use MQTT before displaying on your PyPortal.

Going Further

If you want to format your message so that it displays information on multiple lines, you can use \n to indicate a new line. Here is an example using data from some sensors pulling data from the OneBusAway REST API:

topic: pyportal/feed1
payload_template: |-
  {{ states('sensor.next_bus') }}mins 
        Then: {{states('sensor.2nd_bus') }}mins 
          and: {{ states('sensor.3rd_bus') }}mins
retain: true
qos: 2

topic: pyportal/feed1
payload_template: |-
  {{ states('sensor.next_bus') }}mins 
        Then: {{states('sensor.2nd_bus') }}mins 
          and: {{ states('sensor.3rd_bus') }}mins
retain: true
qos: 2

For this to work well you would also want to add triggers for each of the sensors, so that data is updated with the latest information for all three sensors.