[Gta04-owner] [Tinkerphones] Status of GTA04A5 production +++ has started +++ video available

[H. Nikolaus Schaller]

Hi,
a short update right from the lab:

> Am 27.09.2016 um 17:07 schrieb H. Nikolaus Schaller <hns at goldelico.com>:
> 
> 
>> Am 27.09.2016 um 16:08 schrieb tgrauss <tgrauss at f-gp.eu>:
>> 
>> The "Solder Paste Dipping" on page 3 is a very interesting chapter. It is more related to BGA soldering than PoP.
> 
> Yes indeed. I have never heard about that and it does not really seem to be a common method in 2016.
> 
> And I am not sure if it would help for the DM3730 - which has no significant difference to the tps65950 on the same board.
> 
> I.e. one 0.4mm pitch BGA makes no problem. One makes big problems, but hadn't made so much trouble in GTA04A4.
> 
> Well there are some, but it is unclear what the difference is.

I managed to rework one of the boards which are known to have a short circuit
by removing the DM3730 and PoP.

Looking at the solder pads after removing the chip did reveal some shorts we
already had seen by X-Ray.

What I have done was to place a very tiny snippet of kapton tape under the
DM3730 so that the BGA balls can not be squeezed as much as before.

This appears to make a difference!

Here is a first sign of activity:

> tذb$U   @D  6:b`U@  @QT,0  @tذb$U   @QT,0  @tذb$U   @D  @tذb$U   @D  @tذb$U   @D  tذb$U   @D  @
> 
> Texas Instruments X-Loader (MLO) 1.4.4ss modified for GTA04 (May 11 2016 - 11:52:00)
> No NAND detected
> OMAP36XX/37XX-GP ES2.1
> Board detected: GTA04A2
> SYSBOOT[5:0]: 0x0f/15
> GMPC Memory: 1
> SDRC Memory: DDR 128MB/bank
> NAND: mfr=0x00 id=0x00
> Reading FAT boot sector
> 
> not there
> Loading u-boot.bin from nand
> Skipped bad block at 0x80000
> Skipped bad block at 0xa0000
> Skipped bad block at 0xc0000
> Skipped bad block at 0xe0000
> Skipped bad block at 0x100000
> Skipped bad block at 0x120000
> Skipped bad block at 0x140000
> u-boot.bin not found or blank nand contents - attempting serial boot . . .
> ## Ready for binary (kermit) download to 0x80008000 at 115200 bps. Press 'M' to break into low level monitor.

which means that the DRAM/NAND wasn't found. This is likely a soldering issue of
my prototyping. But the DM3730 BootROM did start and load something from the µSD
card into SRAM. And did activate the UART3.

The big question I have discuss with the production company is how to
glue this very small patch of kapton tape during production...

BR,
Nikolaus