MC7455 9008 Device

[Bjørn Mork]

Noah Taber <noahtaber at gmail.com> writes:

> There are 2 things that I can think of that would have caused the modem to
> be in this state:
>
>    1. I advised my colleague to run the following
>    command"at!usbcomp=1,1,505." This should have enabled the DM, NMEA, RMNET0
>    and RMNET1 interfaces on the mc7455.  My colleague runs an MC7354 in his
>    cradlepoint router.  Those are the interfaces that were enabled when the
>    MC7354 was plugged in, except for RMNET2 and RMNET3 which the MC7455
>    doesn't have (right?).
>    2. Plugging the MC7455 into the cradlepoint router after running the
>    command above.
>
> What are your thoughts?  Hopefully I didn't advise him to brick his own
> MC7455 with the command.

I think that command should be pretty safe. And if the modem is really
showing a 9008 PID (and Qualcomm VID?) then I believe it's unlikely that
command caused it alone.

> I've enabled and disabled many of the interfaces many times on the
> MC7455 and never had a problem.

Uhm, yes, let me admit one of my early mistakes with an MC7455: This was
running a very early firmware version, which allowed a few more
interesting gadgets than the current AT command interpreter does.  So I
tried out a combination with "audio".  This ended up with a boot loop,
which after a while was broken out of by the bootloader failsafe
mechanism.

Took me a while to figure out how to get from there and into a working
state again.  But the fix was basically just getting QDL going and do a
firmware upgrade.  This was way before qmi-firmware-update, though, so
these things weren't so easy then :)

However, I don't think this story is relevant because:
a) my modem never changed from the Sierra VID/PID (bootloader), and
b) my command was definitely unsupported, as shown by the fact that it
  has been removed from the AT command interpreter, while yours is one of
  the common and supported variants

I just wanted to share it because it is an example of the "at!usbcomp"
not always being 100% failsafe.  Although I think that might have been a
bug related to the early firmware I mentioned.  I have done many such
changes with later firmware versions and never had any similar problems.

Plugging the modem into the router is more likely to have caused such
serious problems IMHO. It's easy to kill flash with static electricity,
for example.


Bjørn