arm-netbook September 2015

arm-netbook@lists.phcomp.co.uk

14 participants
14 discussions

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

2024

2023

2022

2021

2020

2019

2018

2017

2016

2015

2014

2013

arm-netbook September 2015