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As you may know Glyn's been working on adding nodered and OpenHAB to the next emonpi image alongside emoncms. Both of these make use of MQTT for their messaging. Emoncms and Emonhub on the emonpi have been using MQTT now for some time however the message format is a little harder to use beyond the emoncms nodes module.

I've added a second format option to the EmonHubMqttInterfacer in the emon-pi variant of emonhub. Its now possible to publish individual node/variables to MQTT, i.e:

    topic: basetopic/emontx/power1
    message: 100

Its possible to use this with the emoncms/scripts/phpmqtt_input.php script. The basetopic has been changed from rx/# to nodes/# in phpmqtt_input.php.

There are a couple of new configuration options in emonhub.conf:

[[MQTT]]
    Type = EmonHubMqttInterfacer
    [[[init_settings]]]
        mqtt_host = 127.0.0.1
        mqtt_port = 1883
        mqtt_user = emonpi
        mqtt_passwd = emonpimqtt2016

    [[[runtimesettings]]]
        pubchannels = ToRFM12,
        subchannels = ToEmonCMS,

        # emonhub/rx/10/values format - default emoncms nodes module
        node_format_enable = 1
       node_format_basetopic = emonhub/

        # nodes/emontx/power1 format
       nodevar_format_enable = 0
       nodevar_format_basetopic = nodes/

By setting nodevar_format_enable = 1 its possible to send messages with this new format or/and its possible to send messages with the node only format.

By default existing systems will not have these lines in emonhub.conf instead the runtime settings looks like this:

    [[[runtimesettings]]]
        pubchannels = ToRFM12,
        subchannels = ToEmonCMS,
        basetopic = emonhub/

Pulling in the latest emonhub.conf will not change emonhub operation as long as the basetopic was emonhub/ prior to the update - which should be most emonpi systems. If you have changed the basetopic please update your emonhub.conf with the new configuration settings in bold above.

I've also added a section on this to the new emonhub configuration documentation page

Emoncms MQTT Input Script 

To import the new MQTT feeds into Emoncms the Emoncms MQTT input script has been updated to subscribe to base topic 'nodes/#'. Be sure to pull in the latest changes (pushed to Emoncms stable branch) 

The Emoncms MQTT input service needs to be installed following these instructions to run the script as a daemon. Here are some example of how the Emocms MQTT input script can be used:

•    create an input from emonTx node called power with value 10:

         nodes/emontx/power 10
     

•      create an input from node 10 called power with value 10 :  

         nodes/10/power 10
         

•      create input from emontx with key 0 of value 10

         nodes/emontx 10
         

•      create input from emontx with key 0 of value 10, key 1 of value 11 and key 2 of value 11:

         nodes/emontx 10,11,12 

Reliability: There is a question about the reliability of the MQTT messages perhaps on the phpMQTT client end, it was detected to a degree in the RF testing. But with a higher volume of messages it may be worse. Id be interested to hear other's experience with it. Update: we did initially test this on the old July 2015 emonPi SD card image, Glyn has since tested with the latest version of Mosquitto (1.4.7) on Raspbian Jessie Lite where reliability appears much better: transmission from RFM69Pi / emonPi > Serial > emonHub > Emocms Inputs.

If further testing is positive we will consider using this MQTT structure for the new pre-built SD card image.