[Community] Wifi, Modem and GPS

[Christoph Mair]

Hi Sven,

On Tue, Jul 15, 2014 at 10:15 AM, Sven Dyroff <S.Dyroff at phytec.de> wrote:
> But please don't forget the possibility that a non-free firmware would allow
> direct communication between UMTS and GPS (if supplied with power) without
> sending any noticeable signals to the outside of the modem.

Yes, the modem firmware could do this, but the modem-integrated GPS
receiver has no connection to any GPS antenna. To route GPS
information from the external GPS chip to the modem you need to
exploit the host CPU as there is no direct connection between these
two modules.


>> The Neo900 includes additional circuitry to detect such bad
>> behavior by measuring the current consumption of the module.
>
> Is this power observation also included within the power line of the modem's
> GPS receiver?

AFAIK the modem has only one shared power line for all internal
modules. I can't remember if the Neo900 will also include an extra GPS
chip to ensure no GPS information is passed to the non-free modem
firmware.

Best regards,
  Christoph