Option driver enhancement

Faidon Liambotis paravoid at debian.org
Thu Oct 4 22:08:31 UTC 2007

Marcel Holtmann wrote:
>> * Multiplex mode, however, is independently useful. As the name implies,
>>   it is a way to talk to more than one part of a GSM modem concurrently,
>>   so you can do stuff like check the uplink quality (or send text
>>   messages ;-) while online. It is entered with AT+CMUX; you may or
>>   may not be able to leave that mode without physically powering down
>>   the USB bus.
>>   The OpenMoko people have written a kernel driver for multiplexing,
>>   but that is still out-of-tree. I'd like that to get fixed.
> we also have a second TTY on these cards, but so far nobody managed to
> decode its protocol. Are you actually sure that the Option card support
> the multiplexer. Last time I checked it seemed they didn't and use the
> second TTY with a binary protocol instead.
All of the Globetrotter Option cards that I've seen (and I've seen
many!) and work with the option driver have a perfectly sane (i.e.
GSM07.07/Hayes AT compatible) management interface.

That doesn't include the PCMCIA<->serial cards (no USB) which only
present one tty.

OTOH, the card embedded on my Dell, which is a rebranded Novatel card
has the binary interface that you speak of.
I've read somewhere that this binary interface is Qualcomm's and it may
be present in other cards too.
It is worth noting that this card errors on AT+CMUX, most probably
because there is already a multiplexing in place.

A webpage[1] suggests that it's not actually binary, it just needs to be
"enabled" by a binary sequence and then it accepts AT commands.
The reverse engineering isn't complete though.
I've also seen a Novatel reverse engineering effort for a completely
different reason[2], even though it's for CDMA/EVDO cards and may be
completely irrelevant.


1: http://wiki.clug.org.za/wiki/Novatel_Status_Port
2: http://www.nynaeve.net/?p=139

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