arm-netbook

arm-netbook@lists.phcomp.co.uk

1079 discussions

Plug computer and FreedomBox-related devices
by Paul Boddie 17 Sep '15

17 Sep '15

Hello, So I was browsing the FreedomBox mailing list when I saw a mention of a plug computer being crowdfunded: http://lists.alioth.debian.org/pipermail/freedombox-discuss/2015- September/006879.html Here's the actual crowdfunding page: https://www.kickstarter.com/projects/1547898916/own-mailbox-the-first-100- confidential-mailbox And the home page of the device: https://www.own-mailbox.com/ So, it seems that the initiators of the campaign have made their own Allwinner A13 board with 256MB RAM and Ethernet support. It is open hardware, apparently, and the software is Free Software, not some kind of proprietary "snake oil" that some privacy campaigns tend to foist on their supporters. It is a bit odd that they've decided to go their own way with the hardware, though. The FreedomBox recommends existing hardware rather than focusing on one particular device: https://wiki.debian.org/FreedomBox/Hardware Another initiative just uses one of the Olimex A20-based products: http://internetcu.be/ Where the product in question looks a lot more capable than the one attempting to be funded above: https://www.olimex.com/Products/OLinuXino/A20/A20-OLinuXino-LIME/open-sourc… hardware Anyway, back to EOMA-68, and a quick search produced a page on the plug computer idea for EOMA-68: http://rhombus-tech.net/community_ideas/plug_computer/ It occurred to me that if only we had EOMA-68 boards out there, maybe people wouldn't be so enthusiastic to go to the trouble of making new boards and running the gauntlet of crowdfunding. There also wouldn't be the artificiality of "stretch goals" where things that should just be happening anyway are punted off into an uncertain future, dependent on the delivery of something that should be separate. Paul

5 13

libre laptop power board, needs 2oz copper, any recommendations?
by Luke Kenneth Casson Leighton 13 Sep '15

13 Sep '15

ok, i checked with the eurocircuits online system, they can't handle the power board. the LTC4155 is handling 4 amps, so the app note says that 2oz copper is needed. however, eurocircuits require a minimum track-to-track clearance of 10mil which is totally incompatible with the distance even between pads of the LTC4155 IC! therefore we conclude, simply, that eurocircuits doesn't have good enough equipment, therefore it is necessary to find an alternative PCB prototyping company. i've managed to get the track-to-track distance to 7mil, smallest via is 10mil with a 24mil ring, track width is a minimum of 8mil, and the size of the PCB is tiny: 3.4in x 1.2in. it's only two layer, components only on one side, but the copper needs to be 2oz. can anyone help with PCB manufacturing at all? tia, l.

3 2

libre laptop 15in pcb progress
by Luke Kenneth Casson Leighton 10 Sep '15

10 Sep '15

eurocircuits report "accepted" after manufacturing the main and the EC PCB prototypes.... they're only 1/2oz copper, literally bare copper, and for $EUR 100 including shipping 2 of each i am really happy with that. components arrived from digikey for the main PCB as well, i can start burning my eyes and singeing my hair some time next week :) l.

1 0

ecocomputing white paper
by Luke Kenneth Casson Leighton 08 Sep '15

08 Sep '15

http://rhombus-tech.net/whitepapers/ecocomputing_07sep2015/ anyone on the IRC channel may have noticed the flood of git commits as i made several successive minor changes and used "git commit" to upload them for proper reading in-place. basically this was written based on the conversations, questions and challenges that people here on arm-netbooks have raised over the years since the list was started, so i particularly wanted to say thank you to all of you for indirectly helping in that way and making it possible to write this white paper in one day. i've been planning it for some time, but there wasn't quite a right time. l.

1 0

libre 15in laptop progress: pcbs and parts
by Luke Kenneth Casson Leighton 05 Sep '15

05 Sep '15

okaaaay sooo, whew :) spent the entire day online looking up digikey part numbers... eyes are going funny (square _and_ crossed....) but i got there. 65 items from digikey, then another 5 or so that need to be sourced from china (only) - a special narrow 3.5mm jack which can re-route both outputs to speakers if the headphone jack's not plugged in, a CM108AH USB Audio IC, GL850G hub, SY6280 USB power control IC and a SY7201 step-up converter for the 3.5 watt LCD backlight. they're all easy to get... just not outside of china. i also ordered qty2 of the PCB1 (main laptop interface board) and PCB2 (embedded controller, keyboard/mouse) as "bare prototype" boards, 0.5oz copper, from eurocircuits. the 4 boards came to a total of $EUR 100, which is pretty amazing for europe, and they were very tolerant about me making a mistake and having to cancel the order, make some changes, and re-submit even after i'd actually paid (they don't normally allow that!). i did have to redesign all the PCBs to use a 24mil surround around the 10mil drill holes - and change all the track-to-track min clearance to 7mil and the min track width to 8mil. this was the *absolute* minimum that eurocircuits "prototype pool" would allow. *sigh* i'm also going to have to go back and adjust the casework to cope with a 1.6mm PCB thickness.... i'd designed it for 1.2mm and yes, really, 0.4mm makes a huge difference, it will be about a day's work to adjust all the 3D parts. the power board (PCB3).... yyyeah i am having fun, there. the example board layout i got from linear tech's online resources says that 2oz copper is needed. *nobody* does 2oz copper with anything below 12mil track and 12mil track-to-track.... yet the distance between the pads on an LTC4155 are 7.8mil (0.2mm)... what's up with that?? soo... hmmm, i'm looking up current handling calculators online to see if i can get away with 1oz copper.... and i believe i can. which would be good, if it was the case, as i can go to eurocircuits.... BUT, i would have to make a "standard" order not prototype because the proto boards are only available in 0.5oz copper... oh! and the 1kW IR solder station arrived. it's.... much more basic than i was expecting :) there are two thermistors that you're supposed to like stick somewhere around the PCB when the 800W pre-heater and the 200W IR lamp are on.... .... i got them in the wrong place on the first board i tried (a 1in prototype board) and was fascinated to see it sizzle within about 15 seconds, this little black spot about 8mm in diameter appeared and i spent the rest of the day with the smell of cooked fibreglass up my nose... mmmm looovely :) anyway it appears that it actually works, must get some solder paste, start doing some desoldering of components on random boards as an experiment, it'll be fuuuun.... l.

1 0

EOMA68 interface update proposal: -GbE, +USB3.1, +GPIO
by Luke Kenneth Casson Leighton 03 Sep '15

03 Sep '15

ok, soo... i've been following the updates to USB3 (10 gigabit speeds now with USB 3.1). in combination with: * the development of both the tablet and the laptop not having room for an ethernet port * the development of lower-cost SoCs not really having ethernet * the fact that the ethernet components cost around $2 when the SoCs themselves are around $2 to $4 ... i'm coming to the conclusion that Ethernet should be removed, and the 9 lines used to * increase the USB3.0 allocation (4 wires) to USB 3.1 (8 wires) * this would leave 5 spare pins for GPIO. * at least two of those should be EINT-capable GPIOs this would make it possible to redesign the tablet PCB to a more "standard" one - removing the need for the I2C GPIO chip for example. if there are any products that need ethernet, it can be done as a USB2 or USB3 compliant external IC. the IC3128 PCB can be reduced down to around a $12 BOM, the EOMA68-A20 PCB can be reduced by a further $2.50. any thoughts or objections, much appreciated the input. l.

3 4

libre laptop 1st and 2nd pcbs off to eurocircuits
by Luke Kenneth Casson Leighton 02 Sep '15

02 Sep '15

ok so i chose the "prototype" option - no solder mask, no silkscreen, just bare copper. the rules for the eurocircuits proto boards are... both strict and also odd. there's a minimum via size which is quite huge (24mil surround, 10mil drill), fortunately however i've been able to design all 3 pcbs around that. i believe it means that there is a big advantage when it comes to production: lower cost! :) also the 1kW IR soldering station is arriving tomorrow, it will be.... interesting to work out how to use it. i will try some experiments first... l.

1 0

libre laptop pcbs
by Luke Kenneth Casson Leighton 28 Aug '15

28 Aug '15

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.

2 2

help needed with a ttl logic circuit
by Luke Kenneth Casson Leighton 25 Aug '15

25 Aug '15

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 start fighting with VCC_SYS_3V3 if EXT_BOOT0 is over 3.3v, so D1 stops that from happening. i think i'm stuck though when it comes to pulling EXT_BOOT0 down to "GND" because actually it will be TTL 0.7v (or so), which, when the diode is taken into account (another 0.7v), i don't think it's enough to switch off the transistor. ... so.... help! what do i do? tia, l.

4 17

libre 15in laptop PCB progress
by Luke Kenneth Casson Leighton 20 Aug '15

20 Aug '15

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.

1 0

Jump to page:

2025

2024

2023

2022

2021

2020

2019

2018

2017

2016

2015

2014

2013

arm-netbook