Using u-blox TOBY-R200, ModemManager not detecting already registered with network

Matthew Starr mstarr at hedonline.com
Mon Feb 5 17:47:00 UTC 2018


> On Mon, 2018-02-05 at 15:45 +0000, Matthew Starr wrote:
> > > On Thu, 2018-02-01 at 22:09 +0000, Matthew Starr wrote:
> > > > I am using a TOBY-R200 which does not support USB Ethernet like
> > > > TOBY-
> > > > L2 models, but only supports AT interface over USB serial.  When I
> > > > use a NetworkManager profile to start a 3G/4G connection using
> > > > ModemManager with the TOBY-R200, the registration step takes a
> > > > long time (~37 seconds).  The modem does eventually connect and
> > > > everything work, but it takes too long for my use case.  When I
> > > > use a u-blox LISA
> > > > U230 modem with the same software configuration, hardware
> > > > platform, and SIM card, I get a connection quickly (~5 second).
> > > > When I put ModemManager in debug mode there is a difference in the
> > > > connection between the two at the registration step as shown
> > > > below. I have the same issue on ModemManager versions 1.4.14,
> > > > 1.6.4, and 1.6.12.
> > >
> > > <snip>
> > >
> > > > On the TOBY R200, instead of realizing that the modem is already
> > > > registered with the network, it runs AT+COPS=0 to reregister with
> > > > the network.  I confirmed that the modem registered with the
> > > > network by checking the AT+CREG?, AT+CEREG?, and AT+CGREG?
> > > > commands.  Here is what ModemManager is outputting when
> connecting
> > > > to the network:
> > >
> > > Do you see this line at all?
> > >
> > > Modem XXX: 3GPP Registration state changed (XXX -> registering)
> > >
> > > Basically, right after enabling the modem, ModemManager should be
> > > running initial registration checks.  That will run a sequence of
> > > AT+CREG?, AT+CGREG?, and AT+CEREG? requests which should report the
> > > operator ID (eg MCC/MNC).  This should all happen before the
> > > connect, but perhaps the NM connect request is happening to quickly.
> >
> > I see that line and waited until that line was output to command
> > Network Manager to bring up the GSM connection. See log below
> >
> > >
> > > Can you include a bit more of the ModemManager debug output from
> the
> > > time the modem is "enabling" until what you show below?
> 
> Thanks; this is a bug in ModemManager but also odd behavior in the
> modem.  This could actually be triggered by your SIM though, given the
> description of the TOBY-R2 series response to the +COPS command in ublox
> document UBX-13002752 (R56).  Anyway:
> 
> (ttyACM1): <-- '<CR><LF>+CGREG:
> 1,"xxxx","xxxxxxxx",6,"6C"<CR><LF><CR><LF>+CIEV:
> 9,2<CR><LF><CR><LF>+CEREG: 4<CR><LF>'
> (ttyACM0): --> 'AT+COPS=3,2;+COPS?<CR>'
> (ttyACM0): <-- '<CR><LF>+COPS: 0<CR><LF><CR><LF>OK<CR><LF>'
> modem_3gpp_load_operator_name(): loading Operator Name...
> (ttyACM0): --> 'AT+COPS=3,0;+COPS?<CR>'
> (ttyACM0): <-- '<CR><LF>+COPS: 0<CR><LF><CR><LF>OK<CR><LF>'
> 
> Here MM is requesting the "set format only" COPS response, then asking for
> the current operator name and number.  The modem replies with "0"
> both times; usually devices are supposed to reply with the MCC/MNC and
> the operator name.  Might be worth asking ublox why the device responds
> this way, but again it could be due to the SIM card.
> 
> Anyway, the modem just isn't giving us any information about the
> MCC/MNC and operator name, despite the fact that it's registered with the
> network and must already know these things.  But MM currently looks to
> see if it has a valid operator MCC/MNC before short-circuiting the automatic
> registration AT+COPS=0 that you're running into.
> 
> Could you try patch below and see if that makes things work better?
> (Attached too just in case my mailer screws up the formatting...)
> 
> Dan
> 

What version of ModemManager is that patch for?  I tried to apply it to version 1.6.12 (the newest version I have) and it failed on several hunks.

Matt


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