IRC log for #qi-hardware on 20150418

01:13.30arossdotmeany advice getting belkin or  serial ups working? not managed to get my small one’s computer interface interfacing.
01:13.42arossdotmeon debain
01:38.40wpwrakfun: a tweet as a measure of code size: http://tweetnacl.cr.yp.to/    "TweetNaCl fits into just 100 tweets"
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11:23.56DocScrutinizer05whitequark: ((http://lab.whitequark.org/images/psu-short/short.jpeg)) I completely fail to grok what that BS with exposed tinned traces and copper fill under mask is meant to establish anyway
11:33.06whitequarkexposed tinned traces for higher current carrying capacity, I'm sure
11:33.34whitequarkwhy do they do that and ALSO add a copper polygon? I've no idea
11:39.28DocScrutinizer05exactly
11:39.45DocScrutinizer05either one or the other, both together is BS
11:40.38whitequarkwell, we've already established they are not the best engineers in the world
11:40.58whitequarkbtw i've got this thing https://imgur.com/a/vEY40
11:40.59whitequark8 bucks
11:41.58DocScrutinizer05awesome and pretty simplistic
11:44.49DocScrutinizer05all the trickery is in the layout, eh? :-D
11:45.23DocScrutinizer05now *that's* a layout you can't do with autorouter ;-)
11:45.47whitequarkindeed
11:46.07DocScrutinizer05true voodoo
11:46.23DocScrutinizer05way beyond my expertise
11:46.35whitequarkafaik no one designs these by hand
11:46.49whitequarkyou take a FEM simulator and basically brute force until you get the results you want
11:46.56DocScrutinizer05yep
11:47.11DocScrutinizer05so actually indeed *sort-of* auorouter
11:47.17DocScrutinizer05autorouter*
11:47.42whitequarkyeah
11:47.49DocScrutinizer05X-band layout is really voodoo
11:48.47DocScrutinizer05when *everything* is a inductivity and a capacitor and a delay line and a phase shifter and a impedance transducer
11:54.47DocScrutinizer05look at http://wstaw.org/m/2015/04/18/plasma-desktopsZ1950.png or even http://wstaw.org/m/2015/04/18/plasma-desktopjg1950.png
11:56.10DocScrutinizer05the latter would be interesting to see the equivalent schematics ;-)
11:56.28DocScrutinizer05I guess it must consist of at least 2 dozen components
11:58.18whitequarkthe former is simple
11:59.23whitequarkit's an LC series circuit tuned at the oscillator frequency
11:59.29whitequarki.e. an RF block essentially
11:59.50whitequarkit's one of the standard shapes apparently
11:59.58whitequarkthe latter is some dark magic
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12:03.46DocScrutinizer05you seem to have found some arcane info sources? :-)
12:04.35whitequarkknow a dude who's into microwave
12:04.59DocScrutinizer05wonders if it would maybe helpful to have a tad if casual learning about that stuff
12:05.07whitequarkhttps://pbs.twimg.com/media/CC1K04kVIAAHkTh.jpg:large
12:05.22DocScrutinizer05wow! ta
12:05.29whitequarkexcept for the microstrip inanity this thing is very simple actually
12:05.50whitequarkthe very thin conductors complete DC circuits
12:06.34whitequarkthe "transistor" is not quite just a transistor, it's an MMIC
12:06.41whitequarkbasically a transistor with an integrated bias circuit
12:06.49whitequarkspecifically for heterodyne resonators like this one
12:10.21DocScrutinizer05aaah
12:11.17DocScrutinizer05I guess BAV99 is rather envelope demod
12:11.51whitequarkBAV99 is just to protect the microwave diode. it has a Vbrkdn of a few V
12:11.54DocScrutinizer05and what they call "IF" is actually the demodulated interference aka beat product
12:12.26whitequarkyeah
12:13.23whitequarkthe "demodulation" (not sure if you can call it so) is the usual result of mixing transmitted with received
12:13.51whitequarkwhere received would shift by a few Hz due to doppler, and you'll get a signal with those few Hz to the left of microwave diode
12:14.32DocScrutinizer05right
12:14.33whitequark(it's not really... modulating anything, it just transmits baseband and looks for shift)
12:14.39DocScrutinizer05ring modulator
12:15.24whitequarkright
12:15.59DocScrutinizer05f1 * f2
12:16.26DocScrutinizer05where f1/2 are signals, not frequencies
12:17.15DocScrutinizer05resulting in f1+f2 and f1-f2, this time frequencies of the signals
12:17.42DocScrutinizer05f1-f2 is what we're interested in here. No demod needed
12:17.48whitequarkexactly
12:20.06DocScrutinizer05I gather the 1202 upper left is a capacitor?
12:20.36DocScrutinizer05to DC-decouple the IF out signal
12:21.28whitequarkresistor
12:21.32whitequarkit's a pulldown
12:21.42whitequarkthe IF signal is not DC balanced :D
12:22.22whitequarkI mean... there's nothing special about these lumped components. the numbered ones are bog standard SMD resistors
12:22.23DocScrutinizer05hmm, ok
12:22.31whitequarkthe white ceramic thing is a DC block capacitor
12:22.44whitequarkagain to protect the microwave diode
12:23.11DocScrutinizer05so the whole ring modulator works completely passive?
12:23.25DocScrutinizer05I.E. no power supply?
12:23.29whitequarkyes
12:23.31DocScrutinizer05DC power
12:23.33DocScrutinizer05wow
12:23.41whitequarkthe only powered thing here is the oscillator
12:23.47DocScrutinizer05:-)
12:23.55DocScrutinizer05as simplistic as it gets
12:24.05whitequarkit works pretty well despite that
12:24.14DocScrutinizer05amazing
12:24.22DocScrutinizer05mere voodoo ;-D
12:24.27whitequarkdetects my hand with hundreds of mV on the IF output, if within 50cm
12:24.49whitequarkdatasheet says up to 20m, I think it will be able to detect large metal like cars in that range
12:24.52whitequarkbut not people
12:24.54DocScrutinizer05ooh, 50cm - yes that's sort of easy
12:25.16DocScrutinizer0520m is absolutely non-trivial
12:25.26DocScrutinizer05considering the signal levels on RX
12:26.34DocScrutinizer05I'm instantly thinking of automatic doors where approaching person needs to get detected in ~2..3m distance, which prolly is what those critters are used for in 99% of installations
12:26.43whitequarkthat is exactly what the description said
12:27.57DocScrutinizer05did they tell anything about directivity of antenna and about how to mount that thing?
12:28.31DocScrutinizer05like "15mm above a metal surface"
12:28.38DocScrutinizer05or whatever
12:29.36whitequarknope
12:29.41DocScrutinizer05:-P
12:30.33whitequarkit's fairly directional
12:30.43DocScrutinizer05I nevertheless guess it would be a good idea to mount it in that way, with the device surface pointing at sensor range
12:31.13DocScrutinizer05I think it is, yes
12:31.47whitequarkhttps://pbs.twimg.com/media/CC0idhkW4AEAgdv.png:large
12:31.47DocScrutinizer05emission in a "8" shape along axis through surface of PCB
12:32.11DocScrutinizer05hey, you got a Rigol?
12:33.07DocScrutinizer05did you already test my rigol scropts?
12:33.11DocScrutinizer05scripts
12:33.38DocScrutinizer05rigol-snapshot already works pretty fine
12:34.06DocScrutinizer05just needs to stop the scope prior to snapshotting, or it will take ages or even fail
12:37.05DocScrutinizer05http://privatepaste.com/139ae36549
12:38.37whitequarkI don't have ethernet at home
12:38.54whitequarkso I just use an usb drive
12:41.42DocScrutinizer05err, you don't have ethernet?
12:42.01DocScrutinizer05how comes?
12:42.50DocScrutinizer05you could link the rigol directly to your PC ethernet jack, not even a crossover patch cable needed with contenptorary NICs that do autodetect
12:43.15DocScrutinizer05honestly, rigol-snapshot is cooool
12:43.59whitequarkI don't have an ethernet jack in my PC :D
12:44.01DocScrutinizer05and a 1000 times more convenient than even the USB hookup to PC
12:44.08DocScrutinizer05wow!
12:44.20whitequarkit's one of the thin ultrabooks, they're too thin for that
12:44.27DocScrutinizer05err
12:44.43DocScrutinizer05USB-attached NIC then?
12:44.45whitequarkI have the USB thingy but it's just annoying to use
12:44.55whitequarkfor occasional use I prefer just the USB drive
12:45.00whitequarkit's permanently plugged into the scope
12:45.09DocScrutinizer05yeah, I had that too
12:45.10whitequarkexcept when extracting data
12:45.32DocScrutinizer05but the unplugging and plugging to PC and copying of files is a PITA
12:46.45DocScrutinizer05honestly, get a http://www.exp-tech.de/usb-ethernet-ax88772b-usb-ethernet-adapter?gclid=CJ6C-rDx_8QCFSP4wgodXCgAEw
12:48.44whitequarkI have one
12:48.47DocScrutinizer05rather sth like http://www.conrad.de/ce/de/product/986780/Netzwerkadapter-100-MBits-EDIMAX-EU-4208-USB-20-LAN-10100-MBits/?ref=category&rt=category&rb=1 - mechanically less dangerous
12:49.06whitequarkI just don't like the extra wires around
12:49.20DocScrutinizer05hmmm
12:49.27DocScrutinizer05how about a proper AP then?
12:49.32whitequarkI mean
12:49.33DocScrutinizer05aka "router"
12:49.34whitequarkthis is my work laptop
12:49.38whitequarkI unplug it all the time
12:49.48whitequarklike every day once or twice
12:49.52whitequarkthis gets old *fast*
12:49.59whitequarkI have a router but it is in the hall
12:50.08DocScrutinizer05ohmy
12:50.12whitequarkbecause the ISP uplink is only long enough to reach the hall
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12:50.41whitequarkI *could* lay cat5 around but it's, again, a pain. I have to do something to doorways
12:50.49DocScrutinizer05you could get a cat5a/6 from ahö to your workbench and to a switch there
12:50.58DocScrutinizer05hehe
12:51.12whitequarkbuilding obviously has no cat5 in walls because the construction company thinks it's still 1990
12:51.49DocScrutinizer05I have sth nice for you: http://www.conrad.de/ce/de/product/971688/RJ45-Netzwerk-Anschlusskabel-CAT-7-UFTP-1x-RJ45-Stecker-1x-RJ45-Stecker-5-m-Weiss-hochflexibel-mit-Rastnasenschutz?ref=searchDetail
12:52.06DocScrutinizer05I got one and they are niiiice
12:52.26whitequarknot bad but 5m is not nearly long enough
12:52.38whitequarkI looked into it and the path it has to take, it'd be at least 10
12:52.58whitequarksort of an unfortunate layout
12:53.07whitequarkmaybe even 15
12:53.52whitequarkDocScrutinizer05: know what that reminds me of? POTS "noodles"
12:54.05DocScrutinizer05http://www.conrad.de/ce/de/product/972502/RJ45-Netzwerk-Anschlusskabel-CAT-7-UFTP-1x-RJ45-Stecker-1x-RJ45-Stecker-20-m-Weiss-hochflexibel-mit-Rastnasenschutz?ref=list
12:54.06whitequarkat least here we call these incredibly shitty "two wires in a flat plastic envelope" POTS cables "noodles"
12:54.19whitequarkhistory goes in circles, etc
12:54.25DocScrutinizer05only 1.8mm "thick"
12:54.37whitequarkthe "noodles" had the advantage that you could nail them to the wall via the plastic in center
12:54.49whitequarkhttp://content.onliner.by/forum/1b1/218/15742/800x800/4ffd918709d5affbf60641507fd9c16a.jpg
12:55.08DocScrutinizer05hehe
12:55.22DocScrutinizer05I wouldn't pierce nails into that cat6 flat cables
12:55.27whitequarkdefinitely
12:55.33whitequarkdoes conrad.de even ship to RU?
12:55.38whitequarkI don't know of any remailer in DE
12:55.44DocScrutinizer05I could, if you don't mind
12:55.52whitequarkhm
12:56.07DocScrutinizer05dunno about conrad
12:56.17whitequarkthat'd work
12:56.27whitequarkon a second thought I'm going to move in a few months hopefully
12:56.30whitequarkso probably no point now
12:56.46whitequarkunless the flat I'm going to rent has an equivalently shitty layout (hopefully not)
12:56.48DocScrutinizer05aaaw
12:57.16DocScrutinizer05take nice things like that cable with you when you move ;-)
12:57.34DocScrutinizer05you can use it again, for sure
12:58.03whitequarkwell... could be
12:58.54DocScrutinizer05anyway, I *strongly* recommend ethernet for Rigol, and when you actually would make up your mind to get decent ethernet and want that cable, just drop me a note with exact instructions how to send
12:59.08whitequarksure
13:02.34DocScrutinizer05meanwhile: http://maemo.cloud-7.de/maemo5/usr/local/bin/rigol-screenshot and rigol* and u1233 there
13:02.50whitequarkI wish sigrok supported rigol
13:02.56whitequarknow *that* would be interesting
13:03.07whitequarkwell, my rigol. it supports some of them
13:04.11DocScrutinizer05I think the err whatever-commands are pretty similar, odds are most stuff works for any rigol
13:04.21whitequarkI looked into adding support
13:04.27whitequarkthey subtly differ in annoying ways
13:04.34whitequarklike one rigol accepts an array and the other a scalar
13:04.34DocScrutinizer05some do, yes
13:04.43whitequarkwho the fuck writes an API like that
13:04.49DocScrutinizer05NFC
13:06.13DocScrutinizer05http://maemo.cloud-7.de/maemo5/usr/local/bin/rigol-waveform
13:07.07DocScrutinizer05which is pretty much WIP
13:14.14DocScrutinizer05but seems to work, well, usually. Though I didn't verify the results yet
13:15.02DocScrutinizer05anyway a downloaded waveform should be sufficient input data for anything like sigrok
13:16.34DocScrutinizer05you're welcome to "upstream" any improvements you make, e.g. regarding buffer depth configured in Rigol (script assumes 24M)  ;-)
13:17.42whitequarksigrok is more than just waveform viewer, it can do stuff like infinite capture
13:17.56whitequarkand configuring the scope
13:18.01DocScrutinizer05which prolly won't work with DS1000
13:18.02whitequarkwhich is the reason to use it
13:18.13whitequarkthe SCPI or whatever commands are there
13:18.18DocScrutinizer05it can't download waveforms realtime
13:18.22whitequarkhm
13:18.29DocScrutinizer05only when stopped
13:18.33whitequarkoops
13:19.54DocScrutinizer05at least afaik
13:21.21DocScrutinizer05even screen snapshots take 3 times as long when running than when stopped. So in my book it's a hw (bus bandwith) limitation
13:22.18DocScrutinizer05quite possibly the ASIC that does all the heavy lifting is hooked up to the communications processor with a flimsy I2C or whatever
13:23.38DocScrutinizer05and the ASIC is not made for doing concurrent communications to processor and same time capturing
13:24.31whitequarksounds about right
13:24.35whitequarkis it even an ASIC?
13:24.37DocScrutinizer05wild guessing, but sort of educated
13:24.45DocScrutinizer05yep, afaik it is
13:25.32DocScrutinizer05I once scrutinized a photo "DS1054 internals"
13:25.57DocScrutinizer05prolly on eevblog?
13:27.45DocScrutinizer05also somebody in that context said sth like "the bandwidth linit on the 50MHz devices is implemented by a simple switchable RC filter in the ASIC's inputs - this is how you enable DS1104"
13:32.47DocScrutinizer05which on second thought makes questionable sense since the DS1000 has a well known dedicated discrete ADC chip. But only one, not 4, and it needs prescalers/amps anyway, which might be part of the ASIC as well
13:36.05DocScrutinizer05anyway once you look at DS1000 screen with that info and from this perspective, you can virtually *see* how messages like "USB connected" etc are sent as bitmap from comm cpu to asic via I2C, for the asic to superimpose them into the display
13:39.47whitequarkgross
13:40.41DocScrutinizer05considering reaction times I wonder how much of stuff like FFT, RS232 decoding etc is done on comm processor as well
13:42.43DocScrutinizer05the low price of the DS1000 is made possible only by very nifty software exploiting the available hw resources to the limit
13:45.00DocScrutinizer05you have a relatively simple ASIC doing the samplig and transcoding sample buffer into a display waveform and raster image, and you got a loosely linked auxiliary processor handling all the switches and communication at large, and also doing the more fancy stuff that includes lots of math or for example the help function etc
13:45.44DocScrutinizer05note how all messages like "function rate limited" or whatever look alike and look awful compared to usual display
13:46.31DocScrutinizer05err "Paramater limited!"
13:47.33DocScrutinizer05and how it akes 400ms between you turning the Y-sensitivity knob "beyond the limit" and the "Parameter linited!" showing up on display
13:47.38DocScrutinizer05takes*
13:48.47DocScrutinizer05sure the asic has some ALU to do for example the left/bottom side value display
13:49.05DocScrutinizer05"Vpp=..." etc
13:52.45DocScrutinizer05also I guess triggering is supported by that ASIC ALU
13:53.19DocScrutinizer05while the whole menu display, RS232 decoding, FFT etc is done on the aux CPU
13:55.11DocScrutinizer05it even seems to me that for unknown reasons all display elements coming from aux CPU are mainly B&W while ASIC is more colorful. I have no real good explanation for that yet
13:56.24DocScrutinizer05possibly a hw limitation in compositor
13:59.46DocScrutinizer05"compositor" I meant the stuff in ASIC doing overlay of data (from aux CPU, e.g. menus) over the display created locally (the colorful waveform and stuff)
14:00.13DocScrutinizer05then otoh those menus have a blue highlight, which voids such explanation
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