MQTT - a very basic question

haffle · 2021-05-02T09:06:06.298Z

Might someone remind me how I check whether an inbound MQTT arrives at my emonPi (which I use as my sole MQTT broker) &/or is then passed on out again?

I have set a separate RPi to send out MQTT messages, but they are not arriving on may Home Assistant instance. Being able to check what is happening on the emonPi will help fault finding.

TIA

dlmpryor · 2021-05-02T12:46:02.591Z

It has been a while since I used MQTT, so I have to dig up some old notes. In the mean time, here is a link that may help.
‘’'Publishing an input with MQTT from an EmonPi - #2 by borpin

haffle · 2021-05-02T14:05:42.130Z

Many thanks @dlmpryor . From that linked thread …

Publishing an input with MQTT from an EmonPi

Anything on the broker under the base topic of emon/ will be processed as an input.

So on the basis that the inbound MQTT messages are not being shown as Inputs within my emonPi, I will take it that the messages are not arriving. They used to, but for some reason stopped, so I will have to investigate why.

A shell script on the other RPi has this content

#!/bin/bash -x
export PATH=/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:/usr/local/games:/usr/games 
sleep 20
rtl_433 -F json -M utc -R 43 | mosquitto_pub -t home/rtl_433 -l -h 192.168.2.50 -p 1883 -u emonpi -P emonpimqtt2016

But there is no home/rtl topic within my emonCMS. And looking at the emonHub log file, I see no reference to the word rtl either. So perhaps it is not being generated on the other RPi.

borpin · 2021-05-02T16:55:55.703Z

haffle:

home/rtl_433

haffle:

But there is no home/rtl topic within my emonCMS.

Emoncms only picks up topics on a base topic you specify (by default emon).

haffle:

They used to, but for some reason stopped

Cannot see how they did. Wrong base topic.

Use an MQTT client and connect to the Broker, then you can see what is appearing at the broker (I use MQTT.fx from the Windows Store on my Win machine).

borpin · 2021-05-02T17:03:03.396Z

BTW, I created a service file for rtl_433 (and suggested it was included).

github.com/merbanan/rtl_433

Service file for systemd

opened 03:45PM - 12 Feb 21 UTC

borpin

enhancement documentation

I think a useful addition would be a service file for rtl_433 ``` # Do not e…dit this file - make changes required via a dropin. # # First create a symbolic link from the install folder to the systemd folder # # sudo ln -sf /home/pi/rtl_433/rtl_433.service /lib/systemd/system # # register the Service file # sudo systemctl daemon-reload # # # Second, create you own set of runtime commands using the systemctl edit mechanism to create a dropin file. # You can replace any of the commands in the standard service file by adding them to the dropin. # as a minimum you will want to edit the RTL_433_OPTIONs environment varialbe with the command line options you want # # sudo systemctl edit rtl_433.service # # Example contents of the dropin (remember it needs the sections in []) # # [Service] # Environment='RTL_433_OPTIONS= -vv -M time:unix -M level -R 03 -R 32 -F "mqtt://<IP>:1883,user=xyz,pass=xyz,retain=0, events=rtl2[/model]"' # # Once the dropin in done, do a daemon-reload again # sudo systemctl daemon-reload # # Start the service - check the syslog or the service status to see if OK. # sudo systemctl start rtl_433.service # # To start the service at boot, enable it # sudo systemctl enable rtl_433.service [Unit] Description=RTL_433 service script StartLimitIntervalSec=5 Documentation=https://github.com/merbanan/rtl_433/README.md [Service] Type=exec # Include a user via the Dropin if required #User=pi Environment='RTL_433_OPTIONS= -vv' ExecStart=/usr/local/bin/rtl_433 $RTL_433_OPTIONS # Restart script if stopped Restart=always # Wait 30s before restart RestartSec=30s # Tag things in the log # View with: sudo journalctl -f -u rtl_433 -o cat SyslogIdentifier=rtl_433 # modify via a dropin to use a dedicated log file for StdOut and StdErr. # NOTE: only works in systemd v236+ # Debain "stretch" includes v232, "buster" includes v239 # Note also the user must be able to create the file and logrotate must be amended to rote the log. #StandardOutput=file:/var/log/rtl_433.log StandardOutput=syslog StandardError=syslog [Install] WantedBy=multi-user.target ``` YMMV

Works well for me

haffle · 2021-05-05T12:35:54.640Z

Thanks @borpin - I am obviously not the only one wanting to do this . I’m afraid that my Linux knowledge is sufficiently low as to not really understand a service file. But FWIW, these are the Dummies notes that I have cobbled together so far concerning restarting after boot …

.
.
.
To make the Raspberry Pi start the process on boot up automatically, do the following

In Terminal type export & look for a line that is similar to
declare -x PATH="/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin"
In my case it was
declare -x PATH="/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:/usr/local/games:/usr/games"

Type sudo nano YOURFILENAME.sh . In the file type (on 4 lines)

#!/bin/bash -x export PATH=/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:/usr/local/games:/usr/games***** sleep 20 rtl_433 -F json -M utc -R 43 | mosquitto_pub -t home/rtl_433 -l -h YOUR_MQTT_BROKER_IP -p 1883 -u YOUR_MQTT_BROKER_USERNAME -P YOUR_MQTT_BROKER_PASSWORD
… and then save it (Cntl+O, ENTER, Cntl+X)

Now make it executable with sudo chmod +x YOURFILENAME.sh

Test that it works by running sudo ./YOURFILENAME.sh and it should be OK.

==============================================
Up until this point all is fine for me, but when I did this yesterday I continued with the next bit but something broke. Not 100% sure my notes are quite right …

Open a new Terminal window and type sudo nano /etc/rc.local and put in it …

cd /home/pi(adjust path as required)
*/the/full/path/to/YOURFILENAME.sh & NB: Don’t forget the “&”; in my case, it was *
cd /home/pi/jjbwatchman.sh &
exit 0 NB: This line should already be there, but I include it here to show where to put these lines

Type sudo nohup ./YOURFILENAME.sh & (don’t forget the &)
Reboot the Pi and it should provide the Watchman data automatically from now on
`

borpin · 2021-05-05T12:38:11.458Z

haffle:

I’m afraid that my Linux knowledge is sufficiently low as to not really understand a service file.

What you have done is actually far more complicated!

haffle · 2021-05-05T12:39:58.035Z

I did get some help with that

haffle · 2021-05-26T16:04:04.250Z

New Question …

I would like to send an MQTT message from Home Assistant to my emonPi which is my MQTT broker. The Topic Name is barns_pv, and this is the Actions section of an Automation.

service: mqtt.publish
data:
  topic: emon/barns_pv
  payload_template: '{{ trigger.to_state.state }}'
  retain: true

Using MQTT Explorer I see that the message is arriving, but it is not within the emon “folder”. How would I change this?

Screenshot 2021-05-26 at 16.52.201158×522 60.3 KB

Is it just a matter of adding a new “node” within emonHub, possibly something like this?

[[17]] #16 is the last node currently listed
nodename = barns_pv
[[[rx]]]
names = #not_sure_what_to_put_here#
datacodes = #not_sure_what_to_put_here#
scales = 1
units = W
whitening = 1

Or something else? Many thanks!