[Gta04-owner] GSM / AT&T Access

Dr. H. Nikolaus Schaller hns at goldelico.com
Fri Sep 2 07:57:46 CEST 2011


Am 02.09.2011 um 02:30 schrieb David Lanzendörfer:

>> Would the GTA04 allow developers to have access to the GSM chip, or
>> the API to allow developers to play around with the GSM radio frequency?
> We got the permission to put all AT-Commandos into our docs.
> The interface is UART, so the only thing WE can provide is
> this documentation and the schematic how this UART is wired
> to our CPU.

It is connected through USB 2.0 (like the sticks you plug into
your notebook). And, there is a 4-wire PCM interface for Audio.

> BUT if you manage to write an alternative firmware
> like it has been done for the GSM-Chip in the GTA02
> then you can certainly do other things then just hopping between
> the base stations and all the usual phone related stuff.

Well, there is less than zero information about writing firmware.
And, there is no known method to change it.

So it is not that we can or can't allow it. We simply buy a black box
modem from OPTION.

This is BTW one of the fundamentally different choices to the
GTA01/02. Developing your own GSM hardware/firmware and
getting it through type approval is far beyond any reasonable
budget.

> I'm not sure I got your question right.
> Maybe you ment Monitoring and Injection?
> Or using is for totally different purposes then GSM?
> Then you will also have the problem of the dimensions of the circuits themself.
> 
>> Also, would the USB OTG host chip be able to provide to full 500mA to power devices with?
> I don't know BUT I wouldn't do that neither.
> Imagine how fast you batteries would be drained this way.

Exacty. There is a charge pump to convert the battery voltage to
5V as needed by USB. This has some less than 100% efficiency.
So let's calculate: 5V at 500mA at 90% efficiency translates to
3.3V at 800mA. Well, the battery has 1200 mAh. So you could
operate such a peripheral for less than 1 hour (the main
system draws something between 200 and 600 mA if not
in sleep).

> If you have electronics, which needs this amount of current
> just patch some Pb-Akkumulator into the circuits as well...
> 
>> Thanks.
> You're welcome
> 
>> I cannot wait for this. I'll be using this phone as part of my University project next year :-D.
> Well...
> Next year?
> What project?
> What university?

That would be interesting information!

BR,
Nikolaus


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