[Gta04-owner] GTA04A5: you will hate and you will love this mail

tgrauss tgrauss at f-gp.eu
Thu Feb 11 08:43:14 CET 2016


Well it is a bad for a good. Good to know that we will have better 
components :)
Do you have an idea when it will go in production or do you have no idea 

Thank you

Best regards

Thierry GRAUSS

On 10/02/2016 20:27, H. Nikolaus Schaller wrote:
> Hi all,
> you might wonder what the status of the GTA04A5 is.
> Unfortunately there has not been much progress since I had to spend 
> much
> more time on making the Pyra (OMAP5) hardware working and verifying 
> that
> it is indeed mass production ready than anticipated. This was really 
> exhausting
> because it was squeezing a phase that would normally need several 
> months
> into just some weeks.
> There had been a lot of details to be fixed. Not much if you see the 
> result,
> but each issue needed 110% attention for several days until a reliable
> fix was found (and some are still open). For example, there were boot 
> problems,
> where the Linux did sometimes start to boot, but suddenly stopped. 
> Sometimes
> it reported CRC errors.
> This turned out to be a 15pF capacitor to attenuate the MMC
> clock signal since it may disturb the GPS receiver (63th harmonic of 
> the
> 25 MHz clock). A lesson we learned twice for the GTA02 and GTA04.
> But this time the 15pF was good for GPS but too much for the MMC.
> It made the MMC interface of the OMAP5 to fail spuriously. Such bugs
> make grey hair and need a lot of time - and can't be parallelised by
> having more people to work on it.
> But now, we are almost through and the OMAP5 is starting to work 
> reliably.
> This has a nice side-effect, which is very important for the GTA04A5 
> project
> and the reason why I report it today.
> The GTA04A5 needs some replacement components because the old
> ones used in the GTA04A3 and A4 are no longer available. Even for
> money.
> One of them is the WLAN/BT combo W2CBW003.
> So the plan is to replace it by a modern WL1835 module [1] which adds
> more WLAN frequencies, speed and adds Bluetooth BLE 4.0.
> But it would be risky to throw it into the schematics, make a PCB
> layout and build the ~100 GTA04A5 we have on plan. The risk is
> that it does not work and we have no chance and money to fix.
> Fortunately, the Pyra also has such a module :) And yesterday, I was
> able to get it alive for WLAN and today for Bluetooth. This means that
> the way it is wired up to the OMAP5 MMC4 interface and UART2 is 
> working!
> And, the way the setup is done in the Device Tree also works.
> Since the OMAP3 is not different for these interfaces, I am now sure
> that we will not make a mistake if we throw in the WL1835 into the
> GTA04A5. This is the good thing! It simply will work with the 4.5-rc3
> kernel (and slightly different commands in user space).
> The other decision blocking the GTA04A5 production is the 1GB RAM/NAND 
> chip.
> Before deciding to solder them all on the ~100 GTA04A5 boards, I would
> like to test it a little with some old (partially broken) GTA04 board.
> This means
> desoldering the original 512 MB PoP (Package on Package) RAM/NAND
> chip. But without damaging the DM3730 CPU. And then solder the 
> different
> PoP chip on top [2].
> Desoldering is easy (since we now have a new vapour phase machine
> with BGA desoldering tools). But soldering a new chip, especially
> Package on Package is really tricky. First experiments did make the
> new chip swim away so that it was soldered in a wrong position :(
> Therefore we have aborted that to find a solution. There are ideas,
> but this needs more experimentation time (i.e. days) until it becomes
> successful. Unfortunately another topic queued up behind making
> the Pyra handheld production ready.
> So I have to apologize that we can't keep the availability date, but
> it is really not much missing. Except time to do what is needed.
> I am really sorry for that delay which might come a little unexpected
> since I did not even give some status updates in the last weeks.
> This is something I promise to change again.
> There is also something on the horizon: a Kernel and QtMoko hacking
> weekend. The plan is to meet in some cosy place and have some core
> hackers just work in two teams to fix remaining kernel issues on one
> side and overhaul QtMoko to run on top of stock Debian Jessie. 
> Replicant
> will also be represented, and we hope that we can then even use our 
> Letux
> standard kernel for Replicant.
> Please let me know if you want to participate/contribute.
> And of course if you have questions about the GTA04A5.
> A final note: we have a new mailing list for Letux kernel development 
> [3]
> so that this list does no longer need to be cluttered by tiny details 
> and patch
> discussions.
> Sorry again for the delay and thanks for your patience.
> -- Nikolaus
> [1]: http://www.ti.com/product/WL1835MOD
> [2]: https://en.wikipedia.org/wiki/Package_on_package
> just a note: we have the "or less" variant in the picture: 0.5mm on
> top and 0.4mm on bottom
> [3]: http://lists.openphoenux.org/mailman/listinfo.cgi/letux-kernel
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