ATZ in enabling_modem_init() step

[Aleksander Morgado]

On Wed, Jul 26, 2017 at 4:32 PM, Tim Small <tim at seoss.co.uk> wrote:
> On 25/07/17 12:47, Aleksander Morgado wrote:
>> A quick solution would be to subclass the enabling_modem_init() step
>> and after running the parent method, run a Telit specific setup to
>> check #CSS? and if disabled due to the ATZ, re-set it, would that
>> work?
>
> I wonder if issuing ATZ is the right thing to do here at all?
>
> It's trying to reset the modem to a well-known state, but ATZ doesn't do
> that - it loads the default user defined profile - which could be
> anything that the user or another piece of software has saved with AT&W.
>

I guess it all depends on the modem in use. Plus, yeah, users may
configure the modem in some way that may then not work correctly with
ModemManager's logic; we have to live with that I'd say. Users may
even configure frequency bands that are not in use in the location
where the modem is trying to run, and MM wouldn't be able to do
anything either. If the user does custom configurations, the user
should deal with problems that may arise from those. MM should only
try to take care of the configurations initiated via APIs provided by
MM; any other use case should be treated out of scope, IMO. That said,
it doesn't mean that users shouldn't do their own configs; but if they
do, maybe it's a good idea to have them done directly via MM, so that
MM can keep the state of what's being done. There are tons of modem
configs, including TTY configs, that we blindly ignore in MM.

> Running AT&F1 once during/after probe might be better to get the modem
> to a known state.
>
> Even more complicated, having just checked the Telit modem CMUX user
> guide - when in CMUX mode both the ATZ and AT&F commands are ignored, so
> it would be necessary to issue AT&F before entering CMUX mode, but
> neither would be an option after that.
>

Are you testing MM with a TTY exposing multiple virtual channels via
CMUX already? How's your setup?

-- 
Aleksander
https://aleksander.es