Passing values from a networked RPi (without HASS.IO) to a HASS.IO RPi via MQTT

Installation Home Assistant OS
1

I need some guidance figuring out the basic logic for the following project:

I want to pass along system and other data from a networked RPi (that has no HASS.IO installation) to the HASS.IO RPi. In the simplest case, that would be the CPU temperature readings of the networked RPi.

I have learned how to publish MQTT messages from the HASS.IO to the other RPi and that works very well.

But how do I send MQTT messages with values back from the other RPi to HASS.IO so that they are being displayed in a HA panel?

Or is this a time for appdaemon? Any thoughts?

2

Here’s an example with a bash script.

1 Like
3

Sounds like the exact match to what I am looking to do. Thanks Rainer, will try this afternoon and report back!

4

I have Paho installed as MQTT client and I just can’t figure out what

/usr/bin/mosquitto_pub -r -t "$TOPIC" -m "$PAYLOAD" -h "$MQTT"

would be for Paho in a non Python shell script.

5

Paho is a python client.
For the bash you need mosquitto-clients.
sudo apt install mosquitto-clients

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6

Sorry for the delay, I now have MQTT with python scripts up and running. Now I just have one question left:

create mqtt sensor in ha

Would you have an example config entry for the sensor acting upon mqtt payloads?

7

You can take the MQTT Sensor or the MQTT Binary Sensor for it.
Here’s the mqtt sensor for the example script.

sensor:
  - platform: mqtt
    name: ha_gw01_i2cbus
    state_topic: 'home/sensors/minibian/i2c_bus'
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8

So I got the MQTT Binary Sensor working fine. Now it’s time to get the MQTT switch working.

I am a bit confused to what exactly state/command/availability topics do. Availability topic as I understand it is a general message if the switch can be reached. It is controlled with “online” and “offline”.
State topic would then be a regular feedback message from the controlled device (as @VDRainer described it in the bash script). I can control it by sending messages with “ON” and “OFF”.
What doesn’t work in my case is the Command message. When I send “ON” or “OFF” to the command_topic nothing happens.

This is what my configurations.yaml looks like:

# MQTT Switch
switch:
  - platform: mqtt
    name: "Bilderrahmen an/aus"
    icon: mdi:panorama
    state_topic: "frame/monitor"
    command_topic: "frame/monitor/set"
    availability_topic: "frame/monitor/available"
    payload_on: "ON"
    payload_off: "OFF"
    state_on: "ON"
    state_off: "OFF"
    optimistic: false
    qos: 0
    retain: true

I am looking for clues why messages to the command_topic don’t cause the Switch to to turn on/off…

9

And if it’s of any help finding out what I may be doing wring, this is the MQTT config part with the topics.

  "mqttusers": [
    {
      "username": "xx",
      "password": "xxx",
      "readonly": false,
      "topics": [
        "frame/monitor",
        "frame/monitor/set",
        "frame/monitor/available"
      ]
    }
  ]
10

I found out where my logic was wrong: command_topic can only be activated through flicking the HA switch directly, it apparently can’t be remote controlled through MQTT.

Now everything works fine! :hugs:

11

For those who are interested in the python script I am using to pass on the information on the display status:

#!/usr/bin/env python3

import paho.mqtt.client as mqtt
import subprocess

client = mqtt.Client()
client.username_pw_set( "username" , "password" )

client.connect("brokerIP", port, 60)

# Send availability notice
client.publish("frame/monitor/available", "online")

# hdmi status display_power
display_status = subprocess.run(['vcgencmd', 'display_power'], stdout=subprocess.PIPE).stdout.decode('utf-8') # check display status
display_status_value = display_status[14:15] # cut display status from result
print(display_status_value) # 0 oder 1

if display_status_value == "0":
    client.publish("frame/monitor", "OFF")
else:
    client.publish("frame/monitor", "ON")
12

And for the CPU temperature:

#!/usr/bin/env python3

import paho.mqtt.client as mqtt
import subprocess

client = mqtt.Client()
client.username_pw_set( "username" , "password" )

client.connect("brokerIP", port, 60)

# Give availability notice
client.publish("frame/cpu_temp/available", "online")

# CPU temperature
cpu_temp = subprocess.run(['vcgencmd', 'measure_temp'], stdout=subprocess.PIPE).stdout.decode('utf-8') # measure CPU temperature
cpu_temp_value = cpu_temp[5:9] # cut temperature from result
cpu_temp_value_int = int(round(float(cpu_temp_value), 0)) # convert string into number, round and make integer
print(cpu_temp_value_int)

client.publish("frame/cpu_temp", cpu_temp_value_int)