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

Neil Jerram neil at ossau.homelinux.net
Thu Feb 11 17:02:39 CET 2016


FYI this is a bit 'tl;dr' for me.  Actually I did read it quite well, but
still struggled to see the overall message - GTA04A5 is still alive but will
take longer than planned?

So, please consider adding a summary.

-----Original Message-----
From: gta04-owner-bounces at goldelico.com
[mailto:gta04-owner-bounces at goldelico.com] On Behalf Of H. Nikolaus Schaller
Sent: 10 February 2016 19:28
To: List for communicating with real GTA04 owners
<gta04-owner at goldelico.com>
Subject: [Gta04-owner] GTA04A5: you will hate and you will love this mail

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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