WP77xx Modem only reachable after sending data (LTE)


I have a problem with the WP77xx modules concerning the data connection.

I have aWP7702 module, from which I can connect to a LTE-M network via a private APN. I’ve verified that it is connected to the private APN and that there is an internet connection. Tested via the Mangoh Red development board.

The modem must be accessible from other devices in the same (APN) network. This means that another device attempts to connect to the modem.

The modem is connected to the network, but does not respond on any external request until data is sent to the network. For example: When I attempt to ping the modem from an external device (in the network), then I get an timeout. However when I ping any (valid) address from the modem then all of sudden the modem responds to the ping requests. When I stop any network activity for a small time period (e.g. 30 sec) then the modem is not (externally) reachable anymore.

It seems that the modem is not activity listening on the network, or even awaiting for any communication. Is this default behavior? If so, can this be changed?

Hope that someone can help me with this issue.

– Bart

Hi Bart,

It’s normal behavior for cellular network. If your device does not have any network’s activity, it will enter to “RRC Idle” mode. With this mode, you can not ping to your device from outside.
It looks like that your private network sets up 30s for inactivity_timer. If you want, you can increase this parameter of your network.
You can use AT!GSTATUS? to show your device in “RRC_Idle” or “RRC_Connect”.
Your device is only reachable if it is in RRC_Connect.
To enter to “RRC_Connect”, it has to start connection or start the Tracking Area Update.
The Tracking Area Update timer could be configured on your network also.
Note that: when the device is in “RRC_Connect” and you make a ping to device, it will never enter to “RRC_Idle”.

Hope it can help.

1 Like

How about disable edrx feature?