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15. MQTT

MQTT (Message Queuing Telemetry Transport) is a lightweight publish/subscribe messaging protocol designed for M2M (machine to machine) communication. MQTT is fast becoming one of the leading protocols for IoT (internet of things) deployments.


Thanks to MQTT support, EEZ BB3 can be easily and securely remotely monitored and controlled. Furthermore, EEZ BB3 can be integrated into existing IoT infrastructure.


For efficient and fast deployment, it is recommended to familiarize yourself with the basic terms of the MQTT protocol. An example of an interaction with EEZ BB3 via the MQTT description protocol is described below using the MQTT Explorer application which is available for free at


Please note that topics are case-sensitive, i.e. <hostname>/system/exec/restart is not equal to <hostname>/system/exec/RESTART.


15.1. Set channel parameter using subscribe topic


Start MQTT Explorer and enter parameters for connection to your MQTT server (aka broker): Name, Protocol, Host, Port, Username and Password.





For example, if we want to set the output voltage on a channel, it will be necessary to type in the Publish section as topic <hostname>/dcpsupply/ch/<ch>/set/u. In this example, the hostname is bb3-zd and to set the output voltage on channel 2 it will be necessary to type as topic bb3-zd/dcpsupply/ch/2/set/u, set its value to 30 (type is json) and click on the Publish button.





The newly set output voltage value will be visible after the topic bb3-zd/dcpsupply/ch/2/umon is refreshed.




15.2. Drawing a topic graph


Select a topic of interest, and click the graph icon in the History section





The default settings graph will appear below the topic list.





Graph settings can be changed by selecting the settings icon.




15.3. Publish topics

15.3.1. System




Returns 0 when EEZ BB3 enters standby mode, or 1 when in active mode


Latest message from the event log formatted as [<event_id>, <event_type>, <event_message>].

For example: [14011, "Info", "Ch2 output on"]


RTC battery voltage


AUX sensor temperature


Cooling fan status and speed


Total active time of the EEZ BB3 (MCU module). Resolution is 1 minute


Duration since the EEZ BB3 was turned on. Resolution is 1 minute

15.3.2. Dcpsupply




Status of the channel output


Returns set output voltage


Returns set output current


Measured output voltage


Measured output current


Measured channel temperature


Channel total active time. Resolution is 1 minute


Duration since the last on time. Resolution is 1 minute

15.4. Subscribe topics

15.4.1. System




Sending 1 initiates EEZ BB3 restart


Send 0 to enter standby mode, or 1 to return back


Initiate trigger system by sending 1


Abort trigger system by sending 1


Displays pop-up message on the EEZ BB3 display


Use to clear text message sent as described above


Recall user defined profile by sending profile number (0 to 9)

15.4.2. Dcpsupply




Sets channel output state: 1 to On or 0 to Off


Sets output voltage


Sets output current


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