[gta02-core] Modem schematic / RF help needed

Dave Ball openmoko at underhand.org
Sun Sep 13 23:30:14 CEST 2009

Rask Ingemann Lambertsen wrote:
> On Sun, Sep 06, 2009 at 03:47:31AM +0100, Dave Ball wrote:
>> I've had a first stab at schematics for the Telit modem.  Comments, 
>> feedback, abuse all welcome :-)
>    The GE865 Hardware User Guide recommends that the antenna trace be
> shielded on all sides by ground traces (page 26). Looking at "3.1.1 BGA
> Balls Layout", I think we should tie GPIO_07 to ground, thereby completing
> the shield of ground balls around the antenna ball. 

I had a look at this too, but didn't think it was worth doing.  Telit 
have clearly designed the ball layout to have ground connections around 
the antenna, and have plenty of NC pins they could have relocated gpio7 
to if it was beneficial to also tie that pin to ground.  It seems that 
they are happy for pin G6 to _not_ be ground, so I'm inclined to follow 
their lead on this.

> What are the chances I could persuade you to move the MODEM_SERVICE and
> MODEM_SLEEP signals from GPJ2/GPJ3 (cpu.sch) to GPC8/GPC9 (lcm.sch) instead?
> Just two signals less on the camera interface.

We had earmarked GPC8/9 for the existing HDQ & LCD_nRES nets, to free up 
the secondary SPI for debug connector.  We do still have GPB4/5 
available, and most of GPA.


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