[GTA04] When is the next and more powerful openmoko releasing
lehner at edv-buero-lehner.de
Sat Nov 13 12:15:23 CET 2010
if you need a XRAY machine again, I could probably help you; I work for
a company which produces those XRay inspection machines.
On Sat, 13 Nov 2010, Dr. H. Nikolaus Schaller wrote:
> Hi all,
> time for another update.
> Am 06.11.2010 um 12:35 schrieb Sylvain Paré:
>> Thanks for the news
>>> Yesterday I received the second board where we
>>> did populate the TPS65950 (power controller).
>>> The results of measurements are:
>>> * the 32 kHz RTC clock is operating
>>> * when inserting a battery, most voltages are
>>> available as expected
>>> Bad news:
>>> * we have a short circuit on the 1V8 rail
>>> I have spent most of the night and this morning to
>>> track this down. It appears to be a solder short circuit
>>> under the TPS chip (a 0.4 mm pitch BGA).
>>> So I am currently sitting at our SMD rework company
>>> and looking over the shoulder of the CTO who has
>>> a lot of experience. Unfortunately I can't make
>>> We already have unsoldered the TPS chip (that needs
>>> a really sophisticated machine) and the short has
>>> The next step is to solder it back again and do the next tests.
>>> If that works, i.e. we get all voltages from the power controller,
>>> the 26 MHz oscillator should also start working.
>>> If that is ok, the OMAP and the POP memory will be soldered.
>>> Maybe we manage to get it today. Then, we can see if the CPU
>>> is doing something.
>> Current status: the 1.8V is now working but the VDD2 (1.2 V) not.
>> The TPS chip aborts the power up sequence early.
> We could solve that by adding a jump start resistor.
>>> Rene will upload some photos of the board and we will
>>> post a link.
> Then, we soldered the OMAP3530 and Pop Memory chip and
> connected RS232:
> It did identify itself as "40W" on the RS232 but did not boot beyond
> that. Fortunately the OMAP has a ROM bootloader (which generates
> the 40W sequence) and we could use it to download a special
> second stage boot-loader that has a simple commandline console
> on RS232. Note that it must fit into 64k SRAM built into the OMAP
> chip. So we are back to C64 times :)
> With this tool, we could identify that the (external) SDRAM has a
> stuck-at-1 error on a single bit-line.
> So we expected another soldering issue and had the OMAP+Pop
> replaced on Monday. But the error pattern remained the same!
> Unexpectedly, we were able to put the board into a 3D X-Ray machine
> on Tuesday (during Electronica Fair). Here are machine & results:
> Fortunately it is *not* a soldering issue. And likely not a PCB production
> Yesterday late at night we found the problem. It is a bad BGA ball assignment
> in our component library. VDDS_MEM (1.8V) is assigned to B17 instead of
> B18. And, B17 is data line 14 of the SDRAM and should have been left NC.
> Therefore we have tied one data line to a high-level...
> I think we can fix that for our samples but it needs some time and we
> run out of components for the samples. Especially memory chips have
> quite a long lead time. For the series version this will be very easy to fix.
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