[Gta04-owner] GTA04A4 starts shipping tomorrow

Gennady.Kupava gb at bsdmn.com
Tue Jan 31 15:30:52 CET 2012


Hello, Nikolaus,

В Пнд, 30/01/2012 в 21:13 +0100, Dr. H. Nikolaus Schaller пишет:
> 
> After 3 days of intensive research (incl. this weekend) we did find the root
> cause: it is the same as it was for the GTA02A5 board [1]. The SD card
> clock. It is 25 MHz and 25 * 63 = 1575 MHz, i.e. the GPS frequency.
> 
> This means that the GTA04 creates some noise which is neglectable
> in more than 5cm distance with an external antenna, but not for the
> active GPS antenna built into the case. And some boards and
> antennas are a little better and others are a little worse so that it
> results in a basically working, but very unreilable receiver.
> 
> The main problem was to find a measurement setup that gave
> reproducible results so that we could not only compare devices, swap
> antennas and try different shielding scenarios, but also check the
> effectiveness of measures against the problem.
> 
> Like with the GTA02 there is a hardware and a software fix. The SW fix
> was to re-enable a feature in the 2.6.32 kernel that we had disabled due
> to problems with the SDIO driver. It appears that it is not at all necessary
> to change anything in the 3.2 kernel. So please forget immediately that
> there is a SW fix :) Because it fixes our unawareness and not a problem...
> 
> The real hardware fix is adding a small capacitor like for the GTA02A5.
> 
> You may wonder why we did not find it earlier. One aspect is testing time.
> The more testing you do the more issues you find. But we simply did
> not have enough GTA04A3 boards to do these tests...

First of all, really nice to see that open phone reached release state.

As i were always wondering about SD reading issues in GTA02, which rises
voltage in driver with reduced clock at beginning, and is not working at
25MHz at all. I wonder can it be related to that capacitor? Are GTA04
users going to experience same speed issues with SD like in GTA02?

Gennady



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