Hi Marko,

 >
> At the end of a PPP connection, garbage was passed in to the AT command
> parser on the modem chat.

Well, the modem should not be passing in garbage in the first place :)

> This garbage contained a doublequote, which switched the AT syntax
> parser into string mode.
> However, because no second doublequote arrived, it stayed in this mode,
> and kept returning UNSURE result.
>

Do you have a trace/hexdump of what is passed on to the GAtChat object?

> I think this is an major issue that should be fixed in oFono.
> The syntax parser has to be extended to handle such cases.
>

Any suggestions on how oFono should detect this condition?

Regards,
-Denis