Arm Mbed OS support forum

Subscription Problem on dashboard page in Device Management


I am connecting to DM with the following device setting. I think It would be a common setting for Pelion.

“mbed-os-pelion-example” codes with NUCLEO_L475VG_IOT01A + BG96 CELLULAR + hologram roaming usim.

After being connected and registered to DM, then I could see my resource value by clicking a resource ID in the Resource tab of the registered device(endpoint name).

In a normal case, at that time I could see an incoming COAP trace log in the UART console which may represent a subscription for the resource I clicked on the dashboard.

But even though I choose the resource on the dashboard, my console doesn’t show any incoming COAP message from time to time.
In that case I waited for a while but nothing of incoming COAP was showed and the dashboard displayed like “can’t get a value”.

After I reset my device, I could see an incoming COAP message for the resource again and also be updated the value on the dashboard.

This problem intermittently happens also when I unsubscribe the resource and choose another one on the dashboard.

I really have no idea what’s wrong about this.
Any try I could do, welcome.

thank you in advance.

Hei @gandalf1 - what connection mode are you using, UDP_QUEUE or TCP?

Cellulars really only work in UDP_QUEUE mode, as they tend to be very aggressive with the sleep. If there is no data to be sent in a while - the modem goes to sleep. This in essence means, that the device is NOT reachable from the cloud point of view. Thus for the cellular cases you must think of the use-case/register update timings, so that they match.

Data sending from the device works, as the modem will wake up for sending. If there is a resource, which is not subscribed (i.e. under observation) - it does not cause any impact, anywhere. Notifications do not get sent out unless there is an observation rule to force it to be sent out. You can use the auto-observable capability, if you wish to send all value changes.