Am 31.01.2012 um 15:30 schrieb Gennady.Kupava: > 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
This is a patch in the GTA02 kernel to reduce noise *without* capacitor. Only GTA02A6 boards have it. > 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? No. It works at full speed, even with capacitor. _______________________________________________ Openmoko community mailing list [email protected] http://lists.openmoko.org/mailman/listinfo/community
