Re: U-Blox modem reconnect

[Denis Kenzior <denkenz@gmail.com>]

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Hi Alexander,

On 07/01/2016 05:22 AM, Alexander Smirnov wrote:
> Dear all,
>
> could you please help me with the following issue. I use U-Blox
> SARA-U270 modem. I'm able to online it and connect to GPRS using both:
> connman and ofono-tests. The problem occurs when modem loses GSM link.
>
> What I did:
>
>   - Boot board with ofono 1.18
>   - activate-context & process-context-settings
>   - ifconfig shows ppp0, everything works
>   - Disconnect physical GSM antenna, network strength becomes 0 (in
> list-modems)

I doubt that this is a good way of testing out-of-coverage conditions. 
You'd probably need a proper network simulator to do that...

>   - Connect antenna, network strength becomes 40
>
> Problem:
>
>   After these steps, modem doesn't reconnect to GPRS, while
> list-contexts shows correct settings:
>
> [ /ublox_0 ]
>      [ /ublox_0/context1 ]
>          Username = t-mobile
>          AuthenticationMethod = chap
>          Protocol = ip
>          Name = Internet
>          Settings = { Interface=ppp0 Netmask=255.255.255.255
> Method=static DomainNameServers=10.74.210.210,10.74.210.211,
> Address=10.23.6.118 }
>          IPv6.Settings = { }
>          Active = 1
>          AccessPointName = internet.t-mobile
>          Password = tm
>          Type = internet
>
> But I don't see ppp0 interface.

Run oFono with AT command logging enabled as well as debugging enabled. 
  See HACKING, 'Running from within the source code repository' section 
for instructions.

>
> An attempt to activate-context doesn't do anything, just empty output
> (with enabled debugging).
>
> Attempt to deactivate-context failed with:
>
> Error deactivating /ublox_0/context1:
> org.freedesktop.DBus.Error.NoReply: Did not receive a reply. Possible
> causes include: the remote application did not send a reply, the message
> bus security policy blocked
>

Most likely because your modem's firmware itself has crashed.

>
> The only hard modem reset helps.
>
> Moreover, after antenna disconnect, there is no more cellular service in
> ConnMan. Only daemon restart helps.
>
>
> How should I handle lose GSM network events to keep ppp0 up? Why ofonod
> hangs with the steps mentioned above?
>

oFono itself is not hung, but the underlying modem has.  Remind me, is 
the SARA a serial based device or USB?

>

Regards,
-Denis