Discussion:
[Arm-netbook] 15in laptop LCD up on PCB1
Luke Kenneth Casson Leighton
2015-12-01 16:05:31 UTC
Permalink
http://rhombus-tech.net/community_ideas/laptop_15in/news/

it's by no means perfect, but i have at least data on-screen. i
suspect EM interference is causing the corruption, so another revision
of PCB1 will need the LVDS IC layout to be reworked. this is however
huge progress. the only 2 parts of PCB1 that need to be checked and
debugged are the MicroSD card slot and the 1W speaker/headphone
amplifier circuits. the CM108AH USB Audio IC has already been
confirmed as operational on the USB bus, as has the GL850G and the 3
USB ports.

l.

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Paul Boddie
2015-12-01 17:25:39 UTC
Permalink
Post by Luke Kenneth Casson Leighton
http://rhombus-tech.net/community_ideas/laptop_15in/news/
it's by no means perfect, but i have at least data on-screen. i
suspect EM interference is causing the corruption, so another revision
of PCB1 will need the LVDS IC layout to be reworked. this is however
huge progress. the only 2 parts of PCB1 that need to be checked and
debugged are the MicroSD card slot and the 1W speaker/headphone
amplifier circuits. the CM108AH USB Audio IC has already been
confirmed as operational on the USB bus, as has the GL850G and the 3
USB ports.
Nice work on getting this far, despite the "gothic" font. ;-)

Now if only the established players would see sense and support this effort
instead of dumping excess stock SoCs into newsagents on the covers of
magazines and causing scuffles in the aisles. :-/ OK, well, maybe not that
established player, but at least the likes of Adafruit and Sparkfun...

Paul

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Luke Kenneth Casson Leighton
2015-12-01 17:38:26 UTC
Permalink
Post by Paul Boddie
Post by Luke Kenneth Casson Leighton
http://rhombus-tech.net/community_ideas/laptop_15in/news/
it's by no means perfect, but i have at least data on-screen. i
suspect EM interference is causing the corruption, so another revision
of PCB1 will need the LVDS IC layout to be reworked. this is however
huge progress. the only 2 parts of PCB1 that need to be checked and
debugged are the MicroSD card slot and the 1W speaker/headphone
amplifier circuits. the CM108AH USB Audio IC has already been
confirmed as operational on the USB bus, as has the GL850G and the 3
USB ports.
Nice work on getting this far, despite the "gothic" font. ;-)
it gets really weird when doing echo "hello" > /dev/tty1 - the
on-screen display is rather... garbled. i'll try a 3rd CPU Card
later, and/or perhaps set up dual-output (via HDMI) to check that it's
not the framebuffer that's corrupted.
Post by Paul Boddie
Now if only the established players would see sense and support this effort
instead of dumping excess stock SoCs into newsagents on the covers of
magazines and causing scuffles in the aisles. :-/
yehhh you saw the report a few days ago by Make magazine, which
showed that the cost of that $5 board is considerably higher:

"Solving this lack of connectivity makes the cost of owning a Pi Zero
increase greatly. It’s not just that you need a USB Wi-Fi dongle,
you’d need a powered USB hub to have a Wi-Fi dongle, keyboard, and
mouse (it only has one USB slot for peripherals; the other is for
power)."

http://makezine.com/2015/11/28/chip-vs-pi-zero/

further down, it shows that the only thing you need to operate the
C.H.I.P is a $1 USB cable, to provide power. the alternative board -
which is "only" $5 - requires a whopping *$19* of additional
components in order to make it actually useful.

l.

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Luke Kenneth Casson Leighton
2015-12-01 18:43:11 UTC
Permalink
On Tue, Dec 1, 2015 at 4:05 PM, Luke Kenneth Casson Leighton
... the only 2 parts of PCB1 that need to be checked and
debugged are the MicroSD card slot
confirmed working. the GPIO pin of the T-FLASH slot had not been
soldered, despite having 260 Centigrade temperatures applied from an
IR heat lamp placed 2cm above it for around 4 minutes. soldering iron
took care of that, and the micro-sd card slot on PCB1 is operational.

that means that the laptop can boot directly from external micro-sd,
now, when using an A20 CPU Card. reason: space is so tight on the
6-layer 43x78mm EOMA68-A20 PCB that it was impossible to route SDC0
over to the *opposite* side of the PCB whilst at the same time
crossing SDC3 in the reverse direction, as the A20 and the DDR3 RAM
take up the centre of the board, leaving very little space for
routing. there are only 3 signal layers (TOP, BOTTOM, layer3).

just the TDA2822 amplifier circuits and the microphone to verify as
operational, and to track down why the LCD is wobbly, and PCB1 is
done.

l.

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Nico Rikken
2015-12-01 21:31:17 UTC
Permalink
Great to see further progress. Keep it up!

At the Dutch T-Dose conference had a couple of visitors at the
FSFE-booth mentioning how great it would be if finally a totally free
laptop would become available. Have referred them to this project
because this seems the only sensible approach to reach this ultimate end
goal, and because it shows just how difficult it is to achieve this goal
in a voluntary effort. Getting a fully free laptop is certainly easier
set then done.

Furthermore I couldn't help but notice that one of the most restricted
laptops in the world is being used to create the most free laptop in the
world.

Regards,
Nico (NL)
Post by Luke Kenneth Casson Leighton
http://rhombus-tech.net/community_ideas/laptop_15in/news/
it's by no means perfect, but i have at least data on-screen. i
suspect EM interference is causing the corruption, so another revision
of PCB1 will need the LVDS IC layout to be reworked. this is however
huge progress. the only 2 parts of PCB1 that need to be checked and
debugged are the MicroSD card slot and the 1W speaker/headphone
amplifier circuits. the CM108AH USB Audio IC has already been
confirmed as operational on the USB bus, as has the GL850G and the 3
USB ports.
l.
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Luke Kenneth Casson Leighton
2015-12-01 22:10:13 UTC
Permalink
Post by Nico Rikken
Great to see further progress. Keep it up!
:)
Post by Nico Rikken
At the Dutch T-Dose conference had a couple of visitors at the
FSFE-booth mentioning how great it would be if finally a totally free
laptop would become available. Have referred them to this project
because this seems the only sensible approach to reach this ultimate end
goal, and because it shows just how difficult it is to achieve this goal
in a voluntary effort.
in a word... yes. i had to make some... interesting design decisions
shall we say - going for example with a custom 3D-printed case instead
of attempting to work with china-based factories [who will not respond
to enquiries for anything less than 10k orders, because they know the
cost of injection-mold casts]. and that took 6 *MONTHS* to complete
the [15] parts needed, which is just a staggering amount of time -
waay more than i was expecting.

keeping it simple - going with USB2 not USB3. cutting out all hard
drives and using USB or MicroSD storage. finding a low-power 15.6in
screen (sub 5 watt). keeping the power consumption to under 15 watts
so that a single-cell battery charger IC could be used instead of
needing multiple cells (which wouldn't fit into the casework design
anyway)...

a whole boat-load of details all of which basically steer things in
ways that you might not have considered at the outset...
Post by Nico Rikken
Getting a fully free laptop is certainly easier
set then done.
yeah. there's quite a few efforts popped up in the past year,
including http://www.powerpc-notebook.org. they're going to run into
the same challenges, and i hope that they have the good sense to read
the reports of the experiences i've encountered along the way, just
like i read the experiences of the openpandora, the kosagi laptop and
other projects and learned from those.
Post by Nico Rikken
Furthermore I couldn't help but notice that one of the most restricted
laptops in the world is being used to create the most free laptop in the
world.
*sigh* i knowww... it's rather unfortunate that the higher perceived
quality of the proprietary software means you end up with a highly
profit-rich company that can afford to purchase the best components
and make the highest quality hardware products. first thing i did
though was blow away the OS, install rEFInd, and boot up debian. i'm
not interested - at all - in the proprietary OS, i want a hardware
product with an exceptionally high resolution screen, light weight,
good build quality, and high specs all round for the money.... and now
that i've got one, i won't replace it for 5-8 years.

at the time i _did_ try to buy an IBM laptop... their web site
failed, at the time, however, preventing and prohibiting me from
giving them any money!

later on i'll be able to tackle creating high-end hardware - not
entirely sure about how to go about that, yet. have to see what SoCs
are available in 5-8 years time, as well as what display output
standards become commonplace.

i can say that i am most certainly *NOT* going to be buying a
smartphone. ever. i bought *nine* HTC hand-helds back around 2002 to
2005, i was one of the early reverse-engineers working on removing
wince from HTC phones and replacing it with openembedded-built
GPE/Familiar based on Angstrom Linux. so i've made the decision: i'm
not going to own another smartphone - ever - unless i've made it
myself.

laptop/workstation however.... yyeah, i have to have something
otherwise i can't get anything done at all!

l.

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joem
2015-12-02 14:49:25 UTC
Permalink
Post by Luke Kenneth Casson Leighton
http://rhombus-tech.net/community_ideas/laptop_15in/news/
it's by no means perfect, but i have at least data on-screen. i
suspect EM interference is causing the corruption
Looks to me like a timing signals error from the CPU
with the LCD driver chip trying to do its best to keep sync.

Need to check with a scope against the specs of the LCD and
what the CPU is generating.
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Luke Kenneth Casson Leighton
2015-12-04 12:39:52 UTC
Permalink
Post by joem
Post by Luke Kenneth Casson Leighton
http://rhombus-tech.net/community_ideas/laptop_15in/news/
it's by no means perfect, but i have at least data on-screen. i
suspect EM interference is causing the corruption
Looks to me like a timing signals error from the CPU
with the LCD driver chip trying to do its best to keep sync.
it's as if the HSYNC - no matter what parameters are used - is
entirely missing. so the LCD takes the very first bits of each line
and uses that as "sync".
Post by joem
Need to check with a scope against the specs of the LCD and
what the CPU is generating.
yehh my scope's only a max of 75mhz (maplin's digital scope)

and i can't ramp things down in order to check, because the 3.4
kernel sunxi lcd code changes the clk_div parameter when the dclk rate
is set lower, such that entirely different code is activated.

tricky...

l.

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