[Arm-netbook] video of 15.6in laptop casework

[Luke Kenneth Casson Leighton]

On Thu, Jul 9, 2015 at 3:44 PM, Wookey <wookey at wookware.org> wrote:
> +++ Luke Kenneth Casson Leighton [2015-07-09 15:01 +0100]:
>> http://rhombus-tech.net/community_ideas/laptop_15in/news/
>>
>> just created a 5min video describing the casework: the parts for the
>> base are now completed, i will move onto the screen next.
>
> That looks really nice, luke.

 thanks.  took long enough :)

> How do the joins work (e.g along the top edge)? Are they screwed or
> slotted or clipped?

 it's.... complicated :)  there are eight pieces involved in the
construction: left, centre and right vertical parts, then front and
back edges, two each, horizontally, and then the touch panel tray.

 the left and right edges have a bolt hole at each end, you can see a
threaded bar sticking out horizontally from all four corners: these
will be M2 phillips screw-headed bolts (or allen key hex-bolts) in the
real thing.

 in each of the front and back parts, a nut is placed into a channel
where it can be pushed down into the right place.  i'm having a
leeetle difficulty with that, the channel is over 15mm deep.

 the front of the vertical edge has, around the bolt hole, an
indentation, and then just above it is a sticking-out bit.

 the end of the horizontal edge has a corresponding sticking-out bit
(bolt hole goes through that, leading to the nut channel), and it has
a corresponding indentation to lock the sticking-out bit from the left
edge.

 both of these together lock the left and front edge absolutely solid
when the bolt is in place.  both sets of
indentation-plus-sticking-out-bit are designed to be injection-molded
using only 2-part molds.

 the back edge is a little more complicated: same principle, but there
has to be a channel running down the middle of the protrusion that
locks into the left edge, because that's where the cable goes.


 the middle part is held with M2 8mm screws.  4 at the back to hold
the back-left and back-right edge.  there is "stepping" in the two
edges, so the screws towards the back actually go down deeper by about
4mm than the ones further towards the front.  the middle part
therefore has a couple of "wings" with corresponding "steps" in it.
i'm going to alter this slightly to be more like the touchpanel.

there are another two screws that are *horizontal* and these go into a
couple of flying wings attached to the middle part, screwing into the
front edge, left and right.  this was a bit of a complicated
arrangement because the wings are off the ground (important when you
think about 3D printing), you can't make the wings too thin because
the screws would break..

the touchpanel part is screwed down in *seven* places.  one is in the
middle (from top)  4 are along the front edge (again top). the front
of the touchpanel has a hidden strut all along its length: this fits
into slots in the front edges.  the idea is not to pack out the entire
touchpanel with plastic (or the front edges) but to leave _just_
enough in each to give some strength so that things don't bend about
due to being weak.  saves the screws a bit from shearing sideways in
their holes.

another 2 horizontal screws into flying wings lock the touchpanel into
the front edges so that both front edges can't rotate about their main
axis.


that's just the main parts - there's some internal parts for the
keyboard tray, battery support, PCB support.

which is why it's taken since.... january to get this far!


> You know what looking at that case made me think of: project ara, with
> a nominally similar concept of a skeleton you put various components
> into (CPU, display, batteries etc). Looking into using the bus they've
> devloped to make bit-swapping more modular might be something to think
> about.

 grrr.  i'm extremely disappointed and angry with google for using -
and extending - a cartel there, based around MIPI.  MIPI LCDs are
*already* cartelled: MOQs are at least 100k units, possibly even
higher: nobody wanting to do a base unit will even get the *slightest*
opportunity there, despite several executives being jailed a few years
ago.  they just got a bit more subtle about it.

 ... and then google went and damn well extended MIPI with this UniPro
stuff.  go look up how many manufacturers of chipsets there are,
there.  first one in - with all the patents - will be the *last* one
in.

 luckily there are a couple of companies just coming out of stealth
mode who have much better architectures than what google came up with.
heck, the first was buglabs and that was *years* ago.

> It's all in the kernel already. The fancy magnetic hot-swap
> connectors will be hard to get currently no doubt, but any connector
> will do to start with.

 yes i figured using 8-pin SIM card connectors would do the job.  8
pins is just enough for USB2, power, I2C and a couple of pins GPIO.
and SIM card connectors are designed to be slim, spring-loaded, you
can PCB-print the pressure-points and gold-plate them... perfect.

 with spring-loading you can even do a side-slide-in module, but i'd
prefer a magnetic latch.

> The major design difference is that there is a core microcontroller on
> the ara design to manage the hotplugging, so that the CPU modules
> aren't special.

 well, USB2 is hot-pluggable.  and it doesn't mind being disconnected.
I2C is ok for hot-swapping if you keep it on a separate bus.

> Anyway this is probably a distraction as you already
> have a plan, but just thought I'd mention it.

 as you can see above, i have... :)  the CPU module form-factor i want
to use is CompactFlash.  connectors are available, easily.  have a 3D
printer, can make casework.

 i've even got a first suitable processor, for the first version: the
Ingenic M150 - it has 128mb of LPDDR2 RAM *on board* in the same IC
package.  i'm not so bothered about the fact that it's only a 1ghz
MIPS, nor about the fact that 128mb of RAM is such a small amount
these days: the space in CompactFlash is unbelievably tight and i at
least want to get _something_ out the door successfully on the first
run that's affordable.

 ... but i'm still concentrating on EOMA68 at the moment.

l.