Hi Enrico,

On 10/03/2014 07:40 AM, Enrico Sau wrote:
> Hi Denis, hi all,
>
> I finally got the network interface working by uninstalling the network
> manager and manually setting the ppp0 interface with parameters
> retrieved from the modem.
>

good

> I have another problem:
> I start the network interface with activate-context python script, and
> stop with deactivate-context script.
> Once I call deactivate-context, I'm no more able to activate it because
> ppp disconnect function calls io_disconnect method, which clears the at
> channel.
> The only way to resume the ppp connection is to disable and re-enable
> the modem in order fot the at channel structures to be filled in again.
>

This is a known issue on some hardware, or may be an issue with the 
modem driver for the hardware you are using.  First some background:

Whenever PPP is disconnected, there are several ways to indicate a hangup:
   1. Send an escape sequence to AT mode, followed by 'NO CARRIER'
   2. Send a low level serial line hang-up

Many modems do both, which results in the tty port being 'closed'.  This 
is why you see the ppp_disconnect being triggered.

oFono understands escape sequences, so #1 is sufficient.  On most 
hardware we can send AT&C0 to disable #2, but some hardware still 
ignores that.

Hardware that uses a high-speed interface (most anything released in the 
last few years) doesn't suffer from this issue.

> Is there any reason for that? Is deactivate-context the correct way to
> temporary stop the network?
>

Yes, that is the correct way, assuming your hardware is well behaved.

Regards,
-Denis