Cloud/LTE re-connection after Loss of Signal

RE: Cloud/LTE re-connection after Loss of Signal

Simonr — Tue, 24 Oct 2023 10:21:27 GMT

Yes, it only uses the pdn_event_handler so you need to add the lte_reg_handler that checks for a disconnect and implements the connection manager as is done in lte_connectivity.c

Best regards,

Simon

RE: Cloud/LTE re-connection after Loss of Signal

sbarnowski — Fri, 20 Oct 2023 02:58:45 GMT

Thanks.

Looking at the Asset Tracker 2 code, it does appear that the pdn_event_handler is implemented. The PDN_EVENT_ACTIVATED event triggers a MODEM_EVT_LTE_CONNECTED event, and PDN_EVENT_DEACTIVATED triggers a MODEM_EVT_LTE_DISCONNECTED event. Like so ...

modem_module.c
/* Handler that notifies the application of events related to the default PDN context, CID 0. */
void pdn_event_handler(uint8_t cid, enum pdn_event event, int reason)
{
	ARG_UNUSED(cid);

	switch (event) {
	case PDN_EVENT_CNEC_ESM:
		LOG_DBG("Event: PDP context %d, %s", cid, pdn_esm_strerror(reason));
		break;
	case PDN_EVENT_ACTIVATED:
		LOG_DBG("PDN_EVENT_ACTIVATED");
		{ SEND_EVENT(modem, MODEM_EVT_LTE_CONNECTED); }
		break;
	case PDN_EVENT_DEACTIVATED:
		LOG_DBG("PDN_EVENT_DEACTIVATED");
		{ SEND_EVENT(modem, MODEM_EVT_LTE_DISCONNECTED); }
		break;
	case PDN_EVENT_IPV6_UP:
		LOG_DBG("PDN_EVENT_IPV6_UP");
		break;
	case PDN_EVENT_IPV6_DOWN:
		LOG_DBG("PDN_EVENT_IPV6_DOWN");
		break;
	default:
		LOG_WRN("Unexpected PDN event!");
		break;
	}
}

However, after placing the Thingy91 into an RF shielded bag for over 10 minutes I never see a MODEM_EVT_LTE_DISCONNECTED event. The cloud just keeps retrying to connect, taking > 10minutes to do so after being removed from the bag.

And assuming I did get a MODEM_EVT_LTE_DISCONNECTED - what should I do with that? Just keep re-connecting to LTE until it connects? Or would re-connecting keep searching until connected, after which the Cloud would connect?

Thanks,

Sebastian

RE: Cloud/LTE re-connection after Loss of Signal

Simonr — Tue, 17 Oct 2023 07:20:08 GMT

I think the reason you're seeing this is that the Asset Tracker v2 application only monitor the PDN. You should use both cell registering messages from the modem and PDN, so that if one of them indicates a disconnect the device will be disconnected. It will go a lot quicker if you use both as you can technically have an active PDN but not be registered to a cell. In lte_connectivity.c we use this approach alongside the connection manager so that will be a better solution. But the backend in the application is intended for supporting both Wi-Fi and LTE.

You can try implementing a check for the disconnect from both the pdn_event_handler and the lte_reg_handler on your end.

Best regards,

Simon

RE: Cloud/LTE re-connection after Loss of Signal

R.J. Helder — Mon, 16 Oct 2023 10:16:40 GMT

We experience te same problems. Our (custom) device has good LTE connection, loses coverage but won't recover its connection in an acceptable period