Receive data to nrf9160 from the server using MQTT

[Rkidechaa]

Hi,

I am developing the system where I am sending the data of three sensors to the server using MQTT. For the above development, I used two microcontrollers one to collect the data from the sensors and nrf9160 to handle MQTT Prorocol.

Also need to add the feature of user-specific data should display. ( user will send the ID no of the sensor to nrf9160 from the server and only that sensor ID data will be display)

I am successfully sending the data to the server using one channel but I now want to implement user-specific.

Question:

1) To receive the data from the server can I use the same channel which I am using to send data to a server?

or do I need to create a different channel for it?

Also, you can suggest me alternate option to implement the above idea.

[Rkidechaa]

Hi,

Håkon Alseth said:

The received data? That is available in the callback handler:

https://github.com/nrfconnect/sdk-nrf/blob/v1.5.1/samples/nrf9160/aws_fota/src/main.c#L196-L227

I am using mqtt_simple sample code to subscribe to one topic and need to store the received data from that subscribe topic.

So where exactly that data stores ?

Håkon Alseth said:

the mqtt library requires that mqtt_input() is called in between each operation.

Note that sending data each 5 minutes will be power consuming for your application. If your application is battery powered, you should consider buffering up data, and sending over the network in larger chunks once per hour for instance. I fully understand that buffering up packets isn't always possible, as latency also plays in as a factor.

Thank you for advice. But we want to plot real time graph from those data. So that is why we chose to send after every 5 min as per battery consideration.

Thanks you,

Rahul

[Håkon Alseth]

Hi,

 

Rkidechaa said:

I am using mqtt_simple sample code to subscribe to one topic and need to store the received data from that subscribe topic.

So where exactly that data stores ?

The data is available when you get the MQTT_EVT_PUBLISH event. I showed that specific sample, because the mqtt_simple did not really show fetching the data clearly.

Please see the same event in mqtt_simple for reference.

 

Kind regards,

Håkon