nRF52840 MQTT-SN Connection to gateway: Retransmission retries limit has been reached

[jelalanne]

Hi,

My architecture is as following {CPU <-> nRF52840 subscriber <-> Raspi + nRF52840 Gateway <-> nRF52840 publisher <-> CPU}

I am working on Paho MQTT-SN programs, and everything was working good until yesterday: I could not connect my end-devices to the gateway anymore using the buttons, as configured in the example code of the nRF52 SDK for Thread v2. I figured out that the problem came from the fact that my raspi was not connected to the internet so not connected to the Broker (I still don't know why it needs to be connected to the broker to accept the connection). 

The problem is, since this morning, I cannot connect the device anymore, with an error "Retransmission retries limit has been reached" when I try to connect to the detected gateway, and I am connected to the internet and able to ping google DNS and even the Broker from the raspi.

If my explanation was not sufficient just ask.

Thanks for your time!

[Edvin]

Hello,

Can you try to enable logging (it should be enabled by default in the 2.0.0 version of the Thread SDK's ncp example). Monitor the log of the NCP chip. Does it throw any errors in the log when you start up or try to connect?

Also, have you tried the Thread Topology Monitor? Are you able to see the network?

Best Regards,

Edvin

[jelalanne]

Hello,

How can I do that?

Thanks

[Edvin]

jelalanne said:

How can I do that?

 What? Monitor the log or the Thread Topology Monitor?

The RTT log can be monitored if you connect a debugger to the ncp device. Then open J-LINK RTT Viewer (you have to download this). It should give you some logging information. You should define DEBUG in your preprocessor defines. When this is done, it should give you some information whether or not the NCP device is running as expected, or if it has crashed. 

The Thread Topology Monitor you can find here:

https://www.nordicsemi.com/Software-and-Tools/Development-Tools/nRF-Thread-topology-monitor

Try it together with one device running the CLI example at first, just to make sure it is up and running before trying to monitor the NCP example. 

[jelalanne]

Thank you for your help!

For those who wants, here is a link to openthread where they explain how to use RTT logging.

https://github.com/openthread/openthread/blob/master/examples/platforms/nrf52840/README.md section " SEGGER J-Link tools"