#qi-hardware IRC log for Sunday, 2011-01-02

wolfspraulwpwrak: looks nice, but what does that antenna graph mean? http://downloads.qi-hardware.com/people/werner/wpan/tmp/atusb-ng-s7.png04:27
wolfspraulwhat's are the fg* and ng* curves04:27
wpwrakwolfspraul: naw, it actually doesn't look so nice. "fg" is the first generation of the atusb boards, "ng" the next generation.04:29
wpwrakwolfspraul: as you can see, i managed to "improve" it by about -10 dB :)04:29
wpwrak.. which means that "ng" isn't the last word on that design :) but first i have to verify a few simpler theories regarding possible design bugs04:31
wolfspraulI see.04:33
wpwraki suspect that i may have put the antenna too close to the rest of the circuit04:35
wolfspraulbtw you said it now days .5-1 days to make one board, what is the time spent on?04:37
wolfsprauls/now days .5/now takes .5/04:38
wolfspraul(no coffee yet :-))04:38
wolfspraulmirko: great news about the rfm12 module!04:38
wpwrakit's about equal parts making the pcb and soldering/testing04:38
wpwrakpcb-making is as follows: 1) put a pcb in the mill (or continue using the one already there - each is currently good for ~8 atusb boards)04:39
wpwrak2) install the drill bit in the mill, then use "make cng" (in atusb/cam2/) to check the position and to adjust the drill bit's heights04:41
wpwrak3) "make drill"04:41
wpwrak4) use "make cng" to replace the drill with an endmill.04:41
wpwrak5) "make mill"04:41
wpwrak6) remove the board, soak the side with the adhesive tape (used to keep the board in place in the mill) with paint remover, then pull off the tape04:42
wpwrak7) make the toner transfer sheets (mark a piece of paper to indicate its position in the tray, make front/back, cut a piece of toner transfer paper to the right size, wipe with alcohol, tape to the paper, make front/back again. do this for both sides)04:44
wpwrak8) scrub one side of the board with steel wool, then clean with alcohol.04:44
wpwrak9) put the transfer paper with the toner side facing up, and the board with the clean copper side facing down. get a piece of adhesive tape and attach it to the board's back (facing up), then position board and tape exactly in on the transfer paper.04:46
wpwrak(position and then fix, with the tape, which is a bit larger than the board)04:47
wpwrak10) cut a strip of paper and tape the "sandwich" on it. fold the paper in the middle so that there's paper above and below the "sandwich". the paper is used for transport and for keeping the sticky-when-hot transfer paper from touching things.04:49
wolfspraulsounds like if you would make a panel, you could save time per board. but of course then you couldn't experiment different things on each board.04:49
wpwrak11) heat up the laminator and send the package through it.04:49
wpwrakyes, i have a pretty high rate of variations in this case.04:51
wpwrak12) when the package comes out of the laminator, cut the board free (leaving the back still covered by tape) and remove the transfer paper. visually check that the traces are good.04:52
wpwrak13) wash the board with water, then gently dry. fix any small defects found with an etch resist pen.04:52
wpwrak14) set up the acid (HCl + H2O2) and etch the board04:53
wpwrak15) wash off the acid with water. then soak the tape with paint remover and peel off the tape.04:54
wpwrak16) repeat steps 7 through 15 for the other side of the board04:54
wpwrak17) visually inspect the board and test for short or broken traces. remove shorts with a cutter, remember interruptions for later repair.04:55
wpwrak18) cover one side of the board with flux, when "paint" solder on it, to cover/protect all the copper.04:56
wpwrak19) do 18 for the other side04:56
wpwrak20) done :-)04:56
wpwrakah, there's a bit more washing after 16, also with paint remover, to remove the toner. then clean the board with alcohol.04:57
wpwraki'm etching the two sides separateley in order to be able to obtain higher accuracy when positioning the toner sheets. with a bit of patience, i get what looks like about 0.1-0.2 mm.04:58
wolfspraulwe should transfer this text into a small README file along with the sources05:00
wolfspraulat least we have it here now and it's archived...05:00
wpwrakmy previous approach, where i did both sides at the same time had a larger error between the toner sheets and even worse between board and sheets. not good enough for boards with pre-drilled holes (back then, i did the holes manually at the end, but that's getting too messy with the huge number of vias i have now)05:00
wpwraki guess i should document the process with some pictures ;-)05:01
wolfspraulsure, even better05:01
wpwraka looong time ago, i did this for an earlier version of the process. lemme find it ...05:01
wpwrakgoing from manual to cnc drilling was a big step forward. i had to build quite a bit of extra sw infrastructure for it (cae-tools/cameo/), but i now have much more precise via holes, i can do proper mechanical mounting holes (e.g., for the USB connector), and i don't go through quite so many broken drills anymore either :)05:13
wpwraki also found a wire that's just the size of the small drill (13.5 mil diameter). so i can put a bit of wire into the hole, and it will stay there, held by friction. before, the wires were loose and thus difficult to solder.05:15
wpwrakthe bottom line is that the 38 vias i have now are less of a pain than the perhaps 10 vias i had on similar boards before05:16
wpwrakwhat still sucks are the ground zones. they quite literally suck, namely heat away from whatever it is i'm actually trying to solder. the experiments with the hot plate resulted in two devices plagued by mysterious defects, so i suspect that process still needs tweaking. for now, i went back to cold boards. (and 100% instead of 0% yield :)05:20
wpwrakadded some more vias that i didn't consider necessary. measurements show that this assessment was amazingly correct. hehe :)06:08
wolfsprauldon't understand06:09
wolfspraulthen why add them?06:10
wolfspraulwhich assessment was correct?06:10
wpwraki added them to confirm that they're really not necessary06:26
wpwrakand another experiment (shorting a cap that appears in some reference designs but not in others) ... also no change. good.06:39
wpwraknow the moment of truth ... what if i replace the antenna with the usual wifi version ...06:40
wpwrakafter disconnecting the pcb antenna, the signal drops by another 15-20 dB. good. the matrix isn't failing just yet :)06:59
qi-bot[commit] David Kühling: add workaround for org-mode problem (todo: need a cleaner fix...) http://qi-hw.com/p/openwrt-packages/297b63107:58
qi-bot[commit] David Kühling: New OpenWrt package for GNU Octave.  Experimental/probably still broken. http://qi-hw.com/p/openwrt-packages/9aaeb4609:23
wolfspraulGNU Octave - cool! That was one of our early dreams of what could run on the NanoNote :-)09:30
viricHello dear qi people.09:33
viricwolfspraul: maybe you remember... I had a "it works for me" solution for offline rss reading09:33
viricFinally I wrote a special purpose program, that should build fine for the nanonote, and work well there.09:34
wolfsprauloh nice09:34
viricwell, it is also in "works for me" state. But a friend started using it too.09:35
wolfspraulok we should make an openwrt package for it09:37
wolfspraulbtw, I saw this recently, not sure you know it... http://newsbeuter.org/09:37
viricah I did not know it09:37
viricI subscribe to lots of comic stripes :)09:38
viricso, not a solution for me ;)09:38
viricIn the nanonote I prefer the approach "offrss + lynx"09:38
wolfspraulcomic stripes?09:40
wolfspraulhow does that work? in text mode?09:40
viriclynx respects the mailcap09:41
viricand can launch fbi to view pictures for example.09:41
wolfspraulwell then, we should package offrss...09:42
viric'offrss' even downloads the images locally.09:42
wolfspraulthanks for sharing the link!09:42
viricI'd be pleased if others use it. :)09:42
viricI'll make a release with version number once I make it look better09:42
viricBut for features, it's in good shape.09:43
wolfspraulok good09:43
viricI'll try to make it work as CGI too, now.09:44
zrafawolfspraul: wiki page: is okey for me :)09:52
qi-bot[commit] David Kühling: Add gfortran compiler support to the toolchain http://qi-hw.com/p/openwrt-xburst/6efd70c10:25
bartbesonce again: gforth guy?10:45
bartbesor really, anyone with a vague interest in gforth10:45
bartbesor forth10:46
wolfspraulyou mean you are looking for someone?10:49
bartbesyeah, I found some nice forth programs not too long ago10:49
viricI wrote some gforth code some time ago10:49
bartbesa word editor and a spreadsheet editor10:49
bartbespretty basic, of course10:49
viricI tried to read the spreadsheet editor10:49
bartbesbut basic is awesome in this case imo :P10:50
viricand I concluded that I don't have enough interest to do anything with it10:50
bartbesI did tic-tac-toe10:50
bartbesbecause I got inspired10:50
viricbartbes: with computer players?10:52
bartbesheh no10:52
bartbesI got lazy10:52
viricI remember the xkcd poster about tic-tac-toe :)10:52
qi-bot[commit] David Kühling: octave: add dependency to fortran runtime lib http://qi-hw.com/p/openwrt-packages/e013ed510:54
qi-bot[commit] David Kühling: octave: fix pager flags to work with busybox'es less http://qi-hw.com/p/openwrt-packages/5d05b1a10:54
zedstaranyone going to fosdem?11:02
viriczedstar: I was thinking about it.11:14
zedstarviric: same here....guess i need to decide soon11:19
viricMy decision will be mainly affected by the price of the flight11:22
zedstaryeh.....seems like plenty of options for accomodation anyway11:24
virichm I'd stay in the home of a friend11:24
wolfspraulif anybody goes to FOSDEM, hold the copyleft hardware flag up high!11:28
wolfspraulmaybe on the mobile side they will all be drooling over their Android gadgets :-)11:28
viricwolfspraul: http://www.codon.org.uk/~mjg59/android_tablets/ did you see?11:29
viric(software related, not hardware, though)11:29
wolfspraulyes I saw it11:29
viricthe big companies are founding more and more BSD-licensed developments11:30
wolfspraullearn from Apple :-)11:30
viricas a way to get more and more closed hardware11:30
viricand software11:30
wolfspraulof course11:30
wolfspraulthis is all squarely heading in the direction of a GPL sandbox11:30
wolfspraulso the Linux kernel can do scheduling, memory management, and USB drivers :-)11:31
wolfspraulbut it's virtualized and all the 'real' investment is happening on the proprietary side11:31
viricEverybody wants linux only for the drivers11:31
wolfspraulof course11:31
wolfspraulwhat's wrong with this strategy?11:31
viricthat this is the only GPL piece they will accept11:31
wolfspraulin a few years, the entire GPL sandbox will be virtualized11:32
wolfspraulthen the problem is contained11:32
viricI don't follow.11:32
viricMaybe I don't understand enough what you mean by 'gpl sandbox'11:32
wolfspraula virtualized guest machine instance, for Linux11:33
viricI don't follow :)11:34
wolfspraulhmm. sorry. What is the question?11:34
viricso you imagine people running Windows, then a virtualisation software that will run Linux (kernel-only), and inside Linux what?11:34
viricor you mean Linux as the host OS?11:35
wolfspraulWindows? no I talk about the embedded world, let's say smartphones/tablets.11:35
viricwell, I meant.. you see Linux as guest os , or host os?11:35
wolfspraulno, the software running directly on the hardware will be a proprietary kernel and features/stacks11:35
wolfsprauland then there will be a virtualized Linux instance11:35
wolfspraulwhich I ironically call 'GPL sandbox'11:35
viricso Linux will know less and less about the hardware.11:36
viricand that propietary kernel will decide what guest OS it allows11:36
wolfsprauloh it will allow and use Linux, why not11:37
viricit could allow Linux signed by someone in particular11:37
wolfspraulit's a nice scheduler and memory manager, and has a bunch of nice drivers too. plus - all free :-)11:37
wolfspraulanyway we see where it goes11:38
viricdo we?11:38
wolfspraulconspiracy theories are not popular, 'tin foil hat' etc.11:38
wolfspraulyes sure11:38
wolfspraulhopefully we can make some really cool copyleft hardware by then11:38
wolfspraulthat's all that matters11:38
wolfspraul"With the Cortex A15 processor, ARM is introducing new technologies that enable hardware virtualization"11:38
wolfspraulI'm so happy the Ben NanoNote has an Android immunization, in the form of 32 MB memory.11:39
wolfspraulthat shot was very effective :-)11:39
viricwolfspraul: also the Loongson3 has x86 virtualisation support11:39
wolfspraulnobody is crazy enough to try to port Android to NanoNote11:39
viricwolfspraul: ah, I could not imagine one single advantadge of 32MB of RAM :)11:40
wolfspraulyeah, but how about that one?11:43
wolfspraulAndroid immunization11:43
wolfspraultough luck for the drois11:43
wolfspraulit was not on purpose, but seriously, it does have that effect11:44
wolfspraulI'm sure if we would have 128 MB memory, someone would have tried already11:44
viricdid it happen with the freerunner?11:44
wolfsprauleven though it's nearly impossible to make a good Android system with 128 mb, you need 256 and more today, 512, etc.11:44
wolfspraulshooting up11:44
wolfspraulso the NanoNote is safe :-)11:44
viricwell, lack of wireless also contributes ;)11:45
wolfspraul[freerunner] hard to say, in hindsight vision is always 20/2011:45
wolfspraulI focus on the Ben now.11:45
viricthank you very much11:45
wolfspraullack of wireless - let's see when Werner's magic boards are working :-)11:45
wolfsprauland mirko made some headway into controlling power switches remotely using HopeRF modules...11:46
viricthat looks very good.11:46
viricaren't there, btw, any minisd to microsd adapters, to be able to use a minisd wifi card?11:46
wolfspraulwe've made some adapters from full size down to our size11:47
wolfspraulbut they are not meant for regular use, too breakable11:47
wolfspraulI think I've made like 10 or 20 of them, and gave away.11:47
viricisn't anyone producing those?11:47
wolfspraulI doubt it.11:48
wolfspraulah well, wait.11:48
wolfspraulI remember googling a while back, and did actually find some pictures.11:48
viricbecause they could go very cheap11:48
wolfspraulI remember finding some online shops listing them, maybe originating from Japan.11:48
wolfspraulbut in any event, those are extremely low volume products11:48
viricwell, I don't imagine a mass public for those.11:48
viricnew antenna?12:12
wpwrakng2 through ng2b are the basic design, with a few small (and ultimately irrelevant) changes12:13
wpwrakng2c is with the antenna cut off12:13
wpwrakng2d is with an external wifi antenna12:13
wolfspraul2d-ref-2 looks good, no?12:13
wpwrakthe different ng2d runs correspond to different positions of the antenna12:14
wpwrakref-2 looks very similar to what i got with the first atusb design: http://downloads.qi-hardware.com/people/werner/wpan/tmp/atusb-ng-s7.png12:14
wpwrakironically, in that one i did almost everything the way they don't tell you to ;-)12:15
wolfspraulok, so for your own pcb antenna, performance is ca. 10dB worse than the best wifi antenna, with particular problems around 2450 mhz?12:16
wpwrakdiscrete balun (instead of integrated), no ground plane on top of pcb next to the antenne (only below), feed line is not impedance-matched12:16
wolfspraulis this a correct interpretation of the graph?12:16
wpwrakyes, in that design12:16
wolfspraulthe only time I see a bump around 2450 even similar to what you consistently see with your antenna is the 2d-ref-012:17
wolfspraulthe bump is at 2455 there and less pronounced, but still12:17
wolfsprauldoes that give you any clue as to why you consistently have this 2450 problem?12:18
wpwraki think the ones in ng2d are mainly imperfections of my test setup (reflections and such)12:19
wpwrakthe deep drop at 2450 looks like a real problem, though. well, i'll see in a bit. now i'm moving this antenna around, too12:19
wpwrakoh, nice. plugged into a laptop, it gets better :)12:20
wpwrakthe fun thing with rf is that i'm never quite sure if i'm not just chasing my own tail ;-)12:21
wolfspraulbtw I am cleaning up the stdout/stderr and exit code handling in my eeschema and pcbnew patches12:22
wpwrakthe laptop is an oqo, which has a full-metal case. best ground you could possible get in a mobile device ;-)12:22
wolfspraulit's not good right now :-) I hope to commit this in an hour or two12:22
wpwrakgreat ! the exit code can be a bit confusing. good to have it gone.12:22
wolfspraulalso stdout/stderr is a mess12:23
wolfspraulrome wasn't built in a day, sorry about that ;-)12:23
wpwrakdidn't notice stdout/stderr :)12:23
wolfspraulit becomes more apparent in the schhist scripts where you do some funky stuff with stdout/stderr12:23
wpwrakaah, i see12:24
qi-bot[commit] Wolfgang Spraul: updated gitsch2ps to new eeschema --plot syntax http://qi-hw.com/p/eda-tools/0f4e2be12:59
qi-bot[commit] Wolfgang Spraul: fixed stdout/stderr and exit code, removed old eeschema --plot http://qi-hw.com/p/eda-tools/7f9de6f12:59
wpwrakand he we have an atusb (ng) board in the oqo. for comparison, -0 is with the board on a cable (like in all previous tests). then i put it into the oqo and moved it around a bit13:02
wolfspraulref-1 seems best13:09
wolfspraulwith "-0 on a cable" you mean some sort of usb extender cable?13:09
wpwrakyes, a usb-a to usb-a cable13:22
wpwrakwolfspraul: here's the receiver, the usrp with a wifi antenna: http://downloads.qi-hardware.com/people/werner/wpan/rflab-rx-refant.jpg13:46
wpwrakwolfspraul: and here are the senders: http://downloads.qi-hardware.com/people/werner/wpan/rflab-atusb.jpg13:47
zearwpwrak, that looks like something you'd use for tortures ;)13:48
zedstarnice to see a blue sky!14:07
qi-bot[commit] David Kühling: octave: fix various shared library rpath problems http://qi-hw.com/p/openwrt-packages/880bca214:16
wpwrakzedstar: you like blue skies ? here's a bit of the view from my office: http://downloads.qi-hardware.com/people/werner/tmp/office.jpg14:19
wpwrakzedstar: alas, my camera doesn't have a good wide-angle, so i can't get it all in one image (and i'm too lazy to stitch them together)14:20
zedstarwpwrak: im jealous!14:22
wpwrakshould i mention that we have a nice 28 C at the moment ?14:24
Action: zedstar growls14:25
wpwrakwolfspraul: i;m bringing you three bens closer to selling out :) need some more devices for experimenting14:28
wolfsprauleh, fantastic!14:29
wpwrakah, you guys created an account for me already :) good that you have a password retrieval feature :)14:30
wolfspraulI plan to remove account creation on the new online shop14:31
wpwrakit's a mixed-blessing kind of feature. can be convenient of you buy a lot from the same place, to avoid problems with typos.14:32
wpwrakon the other hand, mandatory account creation is annoying for one-time customers. but you have both options, so that seems reasonable.14:32
wolfspraulI think not collecting and storing customer data is a feature. Handle the transaction, then purge all unnecessary data, handle the warranty stuff in an anonymous way.14:34
wolfspraultogether with making every unique ID on the device both documented and removable that's going to be a challenge :-)14:34
wpwrakit's a risk/liability reduction feature at least :)14:46
wpwraklet's see how long the toys take. and tomorrow, the same with digi-key :)14:54
wolfspraulthanks a lot for the order!14:59
wpwrakwe have to work together to beat ron's forecast ! ;-)15:00
wolfspraulyeah, ron...15:00
wolfspraulnow he tries to poke into our Milkymist fun15:00
wpwrakhe's good. knows exactly the right questions ;-)15:00
wolfspraulyes and no. wrong perspective. he should think about free software first.15:01
wolfspraulsure if you leave that out, his questions are spot on.15:01
wolfspraulsay if we were Apple.15:01
wolfspraulbut it's good he's around, keeps me grounded15:02
lekernelhe should simply _do_ stuff instead of gawking and asking trivial questions that i've heard a thousand times15:02
wolfspraulsure, he will never :-)15:02
wpwrakwell, the power consumption of that fpga is likely to be something to worry about.15:03
wpwrak(in due time :)15:04
qi-bot[commit] Werner Almesberger: atusb.brd: increased RF ground zone http://qi-hw.com/p/ben-wpan/fd76be616:05
kristianpaulnewsbeuter is nice i use it, kind of ram eating unless you limit the number of items16:08
lekernelmupdf on milkymist: http://www.milkymist.org/fn_mupdf.jpg19:58
lekernelwpwrak: you see i'm using software libraries when they're good. I didn't write my own pdf rendering lib :)19:58
wpwrakhehe ;-)20:04
lekernelactually, flickernoise links against ~12 libraries that I didn't write for the most part...20:06
lekernelfortunately there's something else than GNU/Linux and X.org :)20:07
wpwrakah, regarding LLHDL, someone (kristianpaul ?) mentioned that there's still one non-free tool in the path, place and route, i think. is this also among the things you plan to replace ? (being an fpga ignoramus, i don't know the whole synthesis process)20:08
lekernelbtw it's pretty amazing that this 80MHz RISC softcore with mupdf is about as slow (or fast?) than kde's okular on my 2.5GHz superscalar dual core20:09
wpwrak(x.org) well, you mentioned kdrive as a more palatable alternative, didn't you ? you'll get there :)20:09
wpwrak(as slow) ah, i've been wondering about the performance and whether there would be any meaningful benchmarks for PDFs20:10
lekernelwell even without any benchmark you can say KDE/X11 is bloated :)20:11
wpwrak(as slow) would be nice to be able to have some data to compare MM1 performance with systems "people know". well, as long as that data looks good. else fix first, publish later ;-)20:11
lekernelit's some 20% faster than microblaze at the same clock frequency20:12
lekernelthat for the CPU power only20:12
wpwrakwhat worries me about things like KDE is the gazillion of helper threads and things they spawn before even beginning to do anything20:12
lekernelwhen rendering, most of the computationally intensive stuff is done with hardware acceleration on the fpga20:12
wpwrakso also the PDF renderer benefits from the hw acceleration ?20:13
lekernelno, it's software only20:13
lekernelall the GUI is entirely software20:13
lekernelI wanted something simple :)20:14
lekernelthough I could still implement hardware accelerated blitting without much trouble20:14
kristianpaulhey nice pic :_)20:14
lekernelaccelerating pdf decoding in hw would mean a lot of work20:15
wpwrakblitting may be useful, particular if your GUI stays away from compositing :)20:15
lekernelI wouldn't do that20:15
wpwrakthat's the sort of work you'd only do for benchmarks ;-) have a little dhrystone engine :)20:16
kristianpaul(hw aceleration) i wonder if rtems people tought on that when developing it...20:17
lekernelno, but contrary to linux, rtems is easy to hack to your needs20:18
kristianpaulsurelly :_)20:18
wpwrakgive it time to get fatter and it'll be just as hard ;-) you'd be amazed how easy it was to get major changes into linux in the old days20:19
kristianpaulget fat is an unfair comparison as when gas expands20:20
kristianpaulwpwrak: i tought linux got fat mainlly because drivers..20:21
kristianpaulwpwrak: but even tought linux can run on my linksys router, thats neat :-)20:22
wpwrakdrivers, architectures, sub-architectures, layers of abstraction, exotic protocols, it's all there20:22
kristianpauloh dear..20:23
wpwrakalso, simple implementations have been replaced by more efficient but more complex ones20:24
wpwrakthink the block I/O subsystem, memory management, SMP, NUMA, ...20:24
kristianpaulso simple is not always efficient at all?20:25
wpwrakthe linux kernel is actually still remarkably clean and simple if you consider all the things it can do20:25
kristianpaulbut all that is actually because hardware require it?20:25
kristianpaulnew complex and big hardware everyday..20:26
kristianpaulso linux should run on it !20:26
wpwrak(simple/efficient) well, think of RCU. that's a non-trival approach that is much more efficient than the traditional solutions for this kind of locking problem20:26
kristianpaulwhat we do to run better...20:26
kristianpaulah yes lets implement all this... you already mentioned20:26
wpwrak(rcu) and they built upon the basic concept, making it even more efficient. but yes, you lose simplicity this way. now you need to read a few research papers before you understand the concept.20:27
kristianpaulof course20:27
kristianpaul(linux kernel is actually still remarkably clean and simple if you consider all the things it can do) i agree20:28
kristianpauli cant complain yet for soemthing i cant do :-)20:28
wpwrakand then, we have linux run on anything from that linksys of yours, to the whole world of pcs, to some huge mainframes. all with the same kernel. in many cases using exactly the same code.20:28
wpwrakthis is a unique archievement. nobody else managed that kind of scalability.20:29
kristianpauljust Milkymist One missing ;-)20:29
kristianpaulin a proper not blamed way20:29
wpwrakyeah. MM1 is somewhere in the middle :)20:29
kristianpaulah the mmu thing :-)20:31
wpwrakyeah, the nommu has to go20:32
wpwrakthen get the arch properly into mainline. put X on top. and then it's just optimization beyond that ;-)20:35
wpwrakmaybe even the wayward guys will eventually make something useable, who knows20:35
Action: kristianpaul learn new word today *wayward*20:37
kristianpauldamn, how usefull dual ported ram are20:38
wpwrakwell, they call it "wayland". but i like "wayward" better ;-)20:38
kristianpaulnot intetionally related with some capricious20:39
kristianpaulhmm i remenber from a funny talk at 27c3 (desktop on linux), that wayland wanted to control the audio stuff in a more low level way..20:40
kristianpaulanyway.. lets see what Linux thinks about :-)20:40
wpwrakah, 27c3 ... what was that thing about making pcbs with a modified ink printer ? did anyone have a look at that ?20:41
kristianpauli did20:41
wpwrakdid it seem reasonable ?20:42
kristianpaullooks interesting concept for me, but LOT of profesional work need to be if that thing wants to get work20:42
kristianpaulsurelly the guy need more poeple involved20:42
kristianpaulreasonable not so much now20:43
wpwrakah, not just "buy printer X, toss away the ink and replace it with acid Y, and you're all set" then20:43
kristianpaulfrom why understand its printer head self disamble after some prints20:44
wpwrakhehe ;-)20:44
kristianpaulwhen he fix that i'll take a look again20:44
wpwraki was wondering how he'd keep the acid from eating the head :)20:44
kristianpaulactually what he metioned is been introduced in reprap project too20:45
kristianpaulis clear that floss injects are next step20:45
wpwrakwhat acid does he print with ?20:45
kristianpaulis not acid20:45
kristianpaulis soemthing avoid acid actually20:45
wpwrakoh, i thought he was etching the board directly20:45
kristianpaulyou need a second step later20:45
kristianpaulmee too20:45
kristianpaulbut no20:45
wpwrakaah. ! so he's printing acid resist and then etches. okay. that should be easier.20:46
kristianpaulsome results he show looked pretty well20:46
kristianpaulbut still too hackish appliance20:47
wpwrak(direct etching) i was wondering what kind of witchbrew he'd use. it would have to be extremely aggressive for direct application.20:47
kristianpaulmy first tought was he finally found the mix to do cheap conductive wires20:48
kristianpaulbut nah..20:48
wpwrakcheap conductive wires ? have you checked silver prices lately ? ;-)20:48
kristianpauls/wires/printed wires20:49
kristianpaulconductive ink is expensive20:49
wpwrakadamw_, DocScrutinizer: Q: if i have a full-speed (11 Mbps) USB interface and i want to add a TVS, what would you consider the highest capacitance for the TVS that's still acceptable ? right now, i use 100 pF.22:04
adamw_wpwrak, second22:05
wpwrakah, 50 pF, it seems. usb 2.0, page 130, figure 7-9.22:07
wpwrakgood. i was planning to go to 33 pF. so that should be fine then.22:08
wpwrakno need to get any fancy < 1 pF parts :)22:08
adamw_you could also check http://www.littelfuse.com/data/en/Data_Sheets/Littelfuse_MLV_MHS.pdf22:09
adamw_page 2, Typical capacitance at 1MHz (1Vp-p)22:10
wpwrakyeah, i've seen that you're using them for xue. i'm a little horrified by the clamping voltage. 42 V !22:10
adamw_hm...yeah...but now you already checked usb 2.0 page 130.22:12
adamw_so you can just directly use it for sure.22:12
adamw_i didn't involve in Xue then, so don't know what value they used.22:13
adamw_i could only suggest that you use our parts as possible if you review that value is fine to you. :)22:14
wpwraki have my eyes set on the 445-2559-1-ND from TDK. 5.5 Vdc working voltage, clamps at 19 V, USD 0.044 for a 10kU reel22:16
adamw_please also check to this good article : http://www.intel.com/technology/usb/download/usb2dg_r1_0.pdf22:17
wpwrakah, the one in xue clamps at 135 V. 42 V is the operating voltage. seems very high to me.22:18
wpwrakhmm, high-speed. things get a little nasty there for sure. "A device that has been tested successfully is based on spark gap technology."22:22
adamw_you don't need to follow Xue, just pick a reasonable value!22:22
adamw_agreed...so the question is that how we estimate a spark gap?22:23
adamw_in advance? well...in practically you should can estimate it first.22:23
wpwrakyeah.  445-2559-1-ND looks friendly. plan B would be the stackpole ESD02A5V5R25VCT-ND. about twice as expensive, but only 0.2 pF. clamps at 25 V (with a slightly more expensive 17 V variant available as well)22:24
adamw_assume first22:24
wpwrak(spark gap) naw, that would be a chip. with built-in spark gap. F1320CT-ND22:25
adamw_carefully when you read that voltage at clamping value...always to see the real curve they plotted in datasheet to pick up.22:25
wpwrakor, better: F2594CT-ND22:25
wpwrakcurves - where available - look reasonable. don't show things too clearly, though.22:31
adamw_page 6 of 445-2559-1-ND, page 8 for comparison of various element.22:31
adamw_are you planning that we need to do ESD test? or just choose a part which can suffer from ESD design-in.22:33
wpwrakjust designing. the c8051f3xx chips need external ESD protection for USB (at least that's what the data sheet says)22:33
wpwrakin fact, in some of my prototypes i just leave it off. 45 cents saved per board ;-)22:35
adamw_for M1005C080MTACS, varistor voltage = 8V22:37
adamw_yeah...no problem on your diy kit or toy. :) but for Ben, yeah...let's take more carefully22:38
wpwrakMTACB ? yes, 8 V -> 5.5 Vdc22:38
adamw_page 8 for discharge waveform is good enough : M1005C080MTAAB / V1mA:8V, do you see that?22:43
wpwrakyes, looks pretty good. and the MTAAB has even a higher nominal clamping voltage than the MTACB22:44
wpwrakalright. i think i have my new TVS. thanks a lot !22:45
adamw_so you will choose 445-2559-1-ND?22:49
wpwrakyeah. (for full-speed)22:50
adamw_ok, cool22:51
qi-bot[commit] Werner Almesberger: Removed drl2gp - it's been merged into cameo. http://qi-hw.com/p/cae-tools/45ee73923:41
qi-bot[commit] Werner Almesberger: cameo: added "rotate" command http://qi-hw.com/p/cae-tools/6f30bab23:41
--- Mon Jan 3 201100:00

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