JemRF Smart Gateway MQTT Tab.

MQTT Details

The MQTT Details page is used to identify the optional MQTT Broker you want data sent to, the access account information and other details. The options allow for custom Client Id used by some public brokers and the optional custom subscribe field. The Smart Gateway can send data to both the monitoring server and MQTT broker or just to one, that is a user option.

The default is a blank page and not connected to any broker. The Reset Form will fill out the MQTT settings with the connection information to use the free JemRF Broker. Once the form is filled out, the Enable activated the connection. The status of the connection will show below the Enable option and at the top of each page. There can be a slight delay between the Enable and the Status update showing connected. The actual connection is not made until there is new data to send. So, depending on how many sensors you have and how often they are transmitting, the connection delay will vary.

The image below shows the MQTT Details page with a successful connection to the JemRF MQTT Broker.

Figure 1 The MQTT Details screen.

Note: When a change is made, it will turn yellow as shown in the Network example. The change will take effect when you press Save and the yellow background will be cleared.

If the connection fails an Error code is displayed and some description:

Error Codes

1 - Success - Authenticated and connected to the broker.
2 - Connection refused - incorrect protocol version
3 - Connection refused - invalid client identifier
4 - Connection refused - server unavailable
5 - Connection refused - bad username or password
6 - Connection refused - not authorized

Note: The Error Code will remain showing the status of the last connection even when the MQTT is disabled..

Note: For changes to be made it is best to Disable MQTT before making changes.

MQTT Formats

The MQTT Agent in the Smart Gateway has four data format options.

1 - JemRF - Send data using the device Id as part of the subscription and the raw data sent from the sensor.
2 - Cayenne - Message format used by Cayenne test broker
3 - JSON - Data is packaged in JSON packet with Device Id in the subscribe and a value and data type message.
4 - SparkplubBv3.0 - Data is encrypted and uses the SparkplugB version 3 format.

Note: Once connected and working, to change format the MQTT agent must first be disabled. Then select the new format and Enable.

JemRF Format

[JemRF ID]

If Temperature Sensor Only
- [Sensor Id]
- - TMPA = 56.07
- [Sensor Id]
- - HUMD = 54.2

Cayenne Format

This format is designed to work with the Cayenne.MyDevices.com test site. The JSON format and the JemRF format are the same for both the Gateway and Sensor.

The Gateway default publish topic is: [Gateway Id]/

With Payloads for:

Temperature:

[sensor Id] = temp,c=27.10

Humidity:

3[SensorId] = rel_hum,p=54.4

Pressure:

5[SensorId] = PA,pa=95

Battery:

2[SensorId] = BAT,v=2.75

The MQTT format for Sensor with default topic:: [Sensor Id]/

Temperature:

500 = temp,c=27.10

Humidity:

510 = rel_hum,p=54.4

JSON Format

This format is a generic format and compatible with Home Assistant servers.

The default topic is: [Sensor Id]/

Example Payloads:

1 For temperature with readings set to Fahrenheit.

[probe id] = [{“temperature”:”78.4”},{“unit_of_measurement”:”F”}]

2 For Humidity with readings in percentage

[probe id] = [{“humidity”:”78.4”},{“unit_of_measurement”:”%”}]

3 For readings by the light sensor, showing level in Lux

[probe id] = [{“light”:”78.4”},{“unit_of_measurement”:”Lux”}]

SparkplugBv3.0

This format follows the specifications detailed at Sparkplug.eclipse.org. Messages are encrypted during transmission from the sender to the receiving application. Data seen and processed by the broker is encrypted.

The JemRF adaptation is the in the default Custom subscribe: spBv1.0/JemRFDevices

Sparkplug messages in JSON format shown below. The first timestamp is message send time, and the second timestamp is the sensor sampled time.

Format Template

{ “timestamp”: 1486144502122, “metrics”: [{ “name”: “My Metric”, “alias”: 1, “timestamp”: 1479123452194, “dataType”: “String”, “value”: “Test” }], “seq”: n }

JemRF Example for temperature sensor 87

For this example for temperature sensor with the Id of 87, the topic would be //spBv1.0/JemRFDevices/DDATA/JRFB827EBC0F6D0/87

The data value example would be:

{ “timestamp”: 1486144502122, “metrics”: [{ “name”: “Temperature”, “timestamp”: 1479123452194, “dataType”: “Float”, “value”: “25.4” }], “seq”: 2 }

Custom Device Id

A special feature of the Smart Gateway allows for changing the Device Id.
By changing the device Id, it allows replacing an existing Gateway and being able to set the new Gateway to the same Device Id.
The result is the MQTT subscribe reference remains the same for data archiving even with a different physical hardware device.
To change the Device Id, you must first disable MQTT to clear address cashing, then Enable the change option as shown in Figure 2.

Note: For making andy changes to the MQTT settings, it is best to Disable MQTT before making changes.

Figure 2 Enable Custom Device Id screen.

Once Enabled you can change the Device Id.

Figure 3 Option to change MQTT Device Id screen.