Picon

libre laptop pcbs

ok,

sooo, i'm nearly ready to begin ordering components, and i found that
eurocircuits do an amazingly cheap deal with a fast turnaround on
2-layer 1.6mm FR4 prototype boards (no masks or silkscreen).  on the
charger IC board i've had to replace one of the power MOSFETs already,
the one that is in the recommended circuit from linear tech has gone
EOL!   so many small details to sort out it's amazing...

l.

_______________________________________________
arm-netbook mailing list arm-netbook <at> lists.phcomp.co.uk
http://lists.phcomp.co.uk/mailman/listinfo/arm-netbook
Send large attachments to arm-netbook <at> files.phcomp.co.uk
Picon

help needed with a ttl logic circuit

hi folks could someone please help analyse this circuit to see if it is correct?

http://hands.com/~lkcl/ttl_logic_circuit.png

the requirement:

* an STM32F's "BOOT0" is, by default "pulled to GND" in order that
"normal" operation happens

* the boot operation needs to be selectable by a GPIO from a main CPU
(TTL, with a different voltage)

* if however the main CPU's GPIO is *DISCONNECTED*, "normal" operation
of the STM32F is required.

so, the main things here are:

* the STM32F is run from a 3.3v supply

* the CPU can be a totally different TTL voltage level from the
STM32F.  it could be 5.0V, it could be 3.3v, it could be 3.0v, it
could be even 1.8v.

* the default behaviour needs to be "pull to GND", even if the input
is floating.

R28 ensures that the transistor is, by default, ON, so that R2 is
connected to GND and thus BOOT0 operates in "normal" mode.

however current will flow from EXT_BOOT0 if it is "high", which would
(Continue reading)

Picon

libre 15in laptop PCB progress

http://rhombus-tech.net/community_ideas/laptop_15in/news/

so i made some screen-shots and annotated them - the PCB designs are
almost done already!

i am thinking of doing the assembly myself, because they are only
single-side components.  if anyone has any suggestions on a low-cost
IRDA BGA / SMD station (i see there is something called a T862 on ebay
and amazon), i would appreciate the advice as i am going to go ahead
fairly soon.

what i am first going to do is get the PCBs made up (they're like $50
not $500!) and, before assembly, check that they're all the right
size, that the parts are likely to go in the right places.  then,
because i will have the actual PCBs like in my hands this time, it
makes sense to do the assembly myself as well.

i want to do this in order to demonstrate to people that even someone
like me who has "basic" skill in soldering can actually consider
making a complex thing like a laptop by using ready-made EOMA68
compliant CPU Cards.... and that it really should not cost a fortune
to do so, either.

that's really what this whole thing is about.  previously though i was
doing 4 layer board designs ($500 for qty 5 prototype PCBs) so that
possibility really wasn't clear.

... now it is.

l.
(Continue reading)

Picon

15in libre hardware laptop PCB progress

ok, so i started last week on the PCBs.

first thing: there's three of them.  the casework, needing to have a
middle strut as well as other internal supports, makes it impossible
to have a single PCB, apart from anything that PCB would be just over
12in wide.  also things need to be on different levels.  so the PCBs
are divided as follows:

* PCB1 - contains the CPU card, I/O connectors, LVDS converter IC, USB
Audio IC, USB Hub, EOMA68 identifier EEPROM, and some ribbon
connectors

* PCB2 - contains an STM32F070 and 3 FPCs: one for the touchpanel LCD
(which has an SPI converter IC on it), one for the capacitive
touchpanel (I2C), and one 16+8 1mm pitch connector for the keyboard.

* PCB3 - contains the battery charger and power IC (an LTC4155) as
well as a battery monitor IC (STC3115) which measures current as well
as voltage.  the LTC4155 is absolutely awesome, it has dual supply
inputs (5V in and USB-OTG), it can be turned round to *supply* 5V
USB-OTG, *and* it can provide up to 3A  <at>  5V as system output.

all three PCBs will be double-sided 2 layer, with components only on
one side.  cheap and cheerful.  PCB3 will need to be 2oz copper
because it's dealing with 4 to 5 amps in places.

PCB1 is deliberately huge so that i have plenty of space to work with.
i have had to do a little bit of rearranging so that there are less
wires crossing over - for example, the MicroSD and the USB (CM108AH)
Headphone jack have now swapped places.  as a result, the micro-sd
(Continue reading)

Vero Apparatus: Another Arm Laptop Project

http://wiki.vero-apparatus.com/

leant of it via #neo900 on freenode thanks to edwin.

_______________________________________________
arm-netbook mailing list arm-netbook <at> lists.phcomp.co.uk
http://lists.phcomp.co.uk/mailman/listinfo/arm-netbook
Send large attachments to arm-netbook <at> files.phcomp.co.uk
Picon

15.6in libre-hardware laptop prototype casework fully assembled

http://rhombus-tech.net/community_ideas/laptop_15in/news/

ok, i'm done with major/minor details of the plastic, got something
that "does the job", may need minor tweaking but for now it's done.
woo!  i'll celebrate tomorrow evening, i have a tennis match in the
afternoon.

next is to do the PCBs, whilst on the back burner sort out tape and a
bezel for the LCD (and touchpanel), etc. etc.

l.

_______________________________________________
arm-netbook mailing list arm-netbook <at> lists.phcomp.co.uk
http://lists.phcomp.co.uk/mailman/listinfo/arm-netbook
Send large attachments to arm-netbook <at> files.phcomp.co.uk
Picon

why i am persisting with this project

several people have left this mailing list, or have become lurkers, or
are no longer actively supporting the project, yet i am absolutely
committed to it despite that.

if you would like to know why that is, this is the reason:

http://www.theautomaticearth.com/2015/08/deflation-debt-and-gravity/

l.

_______________________________________________
arm-netbook mailing list arm-netbook <at> lists.phcomp.co.uk
http://lists.phcomp.co.uk/mailman/listinfo/arm-netbook
Send large attachments to arm-netbook <at> files.phcomp.co.uk
Hans-Christian Jehg | 24 Jul 23:19 2015
Picon

Re: 15.6in laptop progress


>On Thu, Jul 23, 2015 at 9:03 PM, Philip Hands <phil <at> hands.com> wrote:
>
>>> then i began work on the friction hinge for the screen lid, so that
>it
>>> will remain upright.  you'd think it would be easy to create an
>>
>> Nope ;-)
>
> you'd be right!
>
>> You could just not bother with a lock.
>
> yehhh the friction hinge isn't accurate enough, there's a few degrees
>of play and that means the lid will be flapping by about... at least 1
>maybe even 2cm once wear sets in.
>
>> I have a Lenovo Thinkpad X230, and it has no lock on the lid.
>>
>> There is a slight impression that the lid snaps shut when almost
>closed,
>> but it's not clear if that's really the case.
>>
>> You could alternatively do some sort of rotating thing on the
>corners,
>> like the OLPC's wifi arials.
>

Magnet(s) to hold the lid closed?

(Continue reading)

Picon

15.6in laptop progress

is there no end to the detail that's needed??

okaay so i started on the screen edge, which (surprise) turned out to
need to be thicker than anticipated.  increasing the thickness by 2mm
had a knock-on effect because, naturally, the base end depth has to be
increased to match.

then i began work on the friction hinge for the screen lid, so that it
will remain upright.  you'd think it would be easy to create an
interlock between two pieces 8mm in diameter that looks aesthetic and
is strong enough, but nooo i can tell you it damn well isn't :)

now i am onto one of the final pieces of the puzzle: creating a lid
lock.  this needs to be spring-loaded (ball-point biro pen spring, cut
into 1/4s 7mm long) and i am kinda amazed at how much detail is needed
in such a small space.  the clasp is 10mm x 9mm x 8mm but requires a
5mm diameter hole in the centre (for the spring)... we'll have to see
how it works out.

l.

_______________________________________________
arm-netbook mailing list arm-netbook <at> lists.phcomp.co.uk
http://lists.phcomp.co.uk/mailman/listinfo/arm-netbook
Send large attachments to arm-netbook <at> files.phcomp.co.uk
Picon

15.6in libre laptop "whoops"...

oh dear, first mistake: hoping it's not too big a deal...

i've done the base, now, and have moved on to doing the LCD screen
holder parts.  i forgot to check which side the connector is... turns
out that when the screen's facing forwards the connector is on the
*right*.... guess which side i put the main PCB?  yep, on the left...

so that shouldn't be so big a deal, right?  just run the cable all the
way along the back of the lcd until it pops out?  noo problem, right?
... except it has to cross the middle part of the LCD, which is where
there is a divider so that the left and right bamboo laminate panels
can "lock" into place, and also so that the top and bottom channels
can be divided into two (so they'll fit across a 200mm x 200mm 3d
printer).

the problem is in joining the parts together.  previously i had
thought to slot a little u-shape in place which would act as a trap:
the ends of each of the U would "lock" into the left and right
edges.... noo problem, right?  except now there's a cable that has to
go through exactly where that joining-piece was supposed to go.

the other option: i was considering mirror-imaging the laptop base.
put the PCB on the right, battery on the left.... except argh i
remembered that i had to *offset* the touchpanel from centre (by about
30mm) in order to fit the battery to its right, and also fit PCB2 so
that the keyboard connector goes into it.... all of this means that
there is absolutely no way that the parts can be mirror-imaged: it's a
near total redesign of the interior, and i'm certainly not doing that.

sooo i have an eeenteresting mechanical design challenge left to think
(Continue reading)

Picon

video of 15.6in laptop casework

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.

l.

_______________________________________________
arm-netbook mailing list arm-netbook <at> lists.phcomp.co.uk
http://lists.phcomp.co.uk/mailman/listinfo/arm-netbook
Send large attachments to arm-netbook <at> files.phcomp.co.uk

Gmane