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 https://mqtt-explorer.com/

 

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

1

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

 

 

 

2

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.

 

 

 

3

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

1

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

 

 

 

2

The default settings graph will appear below the topic list.

 

 

 

3

Graph settings can be changed by selecting the settings icon.

 

 

 

15.3. Publish topics

15.3.1. System

Topic

Description

<hostname>/system/pow

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

<hostname>/system/event

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

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

<hostname>/system/pow/battery

RTC battery voltage

<hostname>/system/pow/auxtemp

AUX sensor temperature

<hostname>/system/pow/fan

Cooling fan status and speed

<hostname>/system/pow/total_ontime

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

<hostname>/system/pow/last_ontime

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

15.3.2. Dcpsupply

Topic

Description

<hostname>/dcpsupply/ch/<ch>/oe

Status of the channel output

<hostname>/dcpsupply/ch/<ch>/uset

Returns set output voltage

<hostname>/dcpsupply/ch/<ch>/iset

Returns set output current

<hostname>/dcpsupply/ch/<ch>/umon

Measured output voltage

<hostname>/dcpsupply/ch/<ch>/imon

Measured output current

<hostname>/dcpsupply/ch/<ch>/temp

Measured channel temperature

<hostname>/dcpsupply/ch/<ch>/total_ontime

Channel total active time. Resolution is 1 minute

<hostname>/dcpsupply/ch/<ch>/last_ontime

Duration since the last on time. Resolution is 1 minute

15.4. Subscribe topics

15.4.1. System

Topic

Description

<hostname>/system/exec/restart

Sending 1 initiates EEZ BB3 restart

<hostname>/system/exec/power

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

<hostname>/system/exec/initiate

Initiate trigger system by sending 1

<hostname>/system/exec/abort

Abort trigger system by sending 1

<hostname>/system/exec/display/window/text

Displays pop-up message on the EEZ BB3 display

<hostname>/system/exec/display/window/text/clear

Use to clear text message sent as described above

<hostname>/system/exec/profile/recall

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

15.4.2. Dcpsupply

Topic

Description

<hostname>/dcpsupply/ch/<ch>/set/oe

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

<hostname>/dcpsupply/ch/<ch>/set/u

Sets output voltage

<hostname>/dcpsupply/ch/<ch>/set/i

Sets output current