Problem with QMOD, Telit Modem and ofono

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Harald Welte laforge at osmocom.org
Mon Oct 14 15:22:41 UTC 2019


Hi Alan.

On Mon, Oct 14, 2019 at 10:19:53AM +0100, KageDS wrote:
> I seem to be hitting a strange problem trying to use a sysmoQMOD with Ofono
> and a Telit Modem (HE910)
> There seems to be a window of around 30 seconds after starting
> osmo-remsim-client-st2 whereby ofono cannot talk to the modem.

Neither I nor sysmocom has any experience specifically with Telit
modems.

I suggest to reduce the problem domain:

* does the modem exhibit that "window" even if used with a physical simcard in QMOD?
* does the modem exhibit that "window" even if used with a physical simcard in some
  other boards (e.g. the OSmocom mpcie-breakout)?
* what kind of USB bus activity (e.g. re-enumeration) do you see?

> It seems that switching from physical SIM to remote SIM causes the modem to
> lock-up for a while.

It is not possible to switch from remote to local or vice-versa without having the
modem powered off, or without having the modem in reset during that time, or at least
issuing a reset after you have switched.

In theory the 3GPP specifications allow for a SIM card to be changed
while the UE is running.  However,in practise all implementations I've
seen in the past 10+ years are lazy and  even those modems that actually
detect this event properly will simply respond to a reset of (at least)
the baseband processor.

So maybe what you're observing is simply the modem rebooting at that point?

Regards,
	Harald
-- 
- Harald Welte <laforge at osmocom.org>            http://laforge.gnumonks.org/
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