U-Blox modem reconnect

U-Blox modem reconnect

[Alexander Smirnov]

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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)
  - 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.

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


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?


-- 
With best regards,
Alexander Smirnov

ilbers GmbH
Baierbrunner Str. 28c
D-81379 München
+49 (89) 122 67 24-0
http://ilbers.de/
Commercial register Munich, HRB 214197
General manager: Baurzhan Ismagulov

Re: U-Blox modem reconnect

[Denis Kenzior]

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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

Re: U-Blox modem reconnect

[Alexander Smirnov]

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Hi Denis,

Thanks a lot for the reply!

>> 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...
> 

I'm not cellular expert, so probably ask dummy things :-) what can be wrong with such test? How it differs from, for example, going underground like metro, or tunnel in highway?

>>  - 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.

Yeah, I've enabled this, but there is no output. The last command was printed when I activated context first time, IIRC it was CONNECT.

> 
>> 
>> 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?

USB, it's connected using ACM Linux driver (ttyACM0-ttyACM6).

Btw: what should be the behavior, when ofono is out from cells coverage? Who should deactivate context, ofono or modem?

Alex

> 
> 
> Regards,
> -Denis
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