IRC log for #neo900 on 20180514

00:00.25*** join/#neo900 atk (~Arch-TK@ircpuzzles/staff/Arch-TK)
00:01.09Joerg-Neo900https://www.we-online.de/web/en/index.php/show/media/04_leiterplatte/2013_1/webinare_1/hdi/02072013_Webinar_HDI_DesignGuide_1_EN.pdf  seems useful
00:02.15houkimethey even have a piece when D+ and D- are run in parallel on different layers
00:03.32houkimeand crossing different numbers of vias
00:03.56Joerg-Neo900note that GTA04 is not exactly a benchmark though
00:04.34Joerg-Neo900I don't even know if USB2.0 speed been tested for signal integrity
00:05.08Joerg-Neo900if we can do better than GTA04 we for sure would want to
00:07.34Joerg-Neo900ideally you verify the layout of such critical traces with a vector network analyzer
00:10.12Joerg-Neo900but in the end it's just a question of "does it work, or doesn't it?"
00:12.34houkimeWell, my problem with design guides now is that they rarely account for extreme situations.
00:13.47Joerg-Neo900hmm. at least that Wuerth design guide webinar has a quite luxury dogbone BGA example on page 29. If only we could do this, we wouldn't need in-pad vias
00:13.59Joerg-Neo900but no way for 0.4 pitch
00:19.15houkimeJoerg, do you have a zap gun?
00:19.39Joerg-Neo900what for :-D
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00:23.46*** topic/#neo900 is http://neo900.org | CCCAMP15 lightning talks at http://neo900.org/stuff/cccamp15/ - major: http://neo900.org/stuff/cccamp15/ccc2015talk/neo900-wpwrak_CCC2015.webm | conversations are logged to http://infobot.rikers.org/%23neo900/ and http://irclog.whitequark.org/neo900 | Latest news: http://neo900.org/news/joerg-pia-2018-03-01
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00:30.41houkimeshould we consider B2B connectors as possible ESD entrypoints. That's the important question
00:30.49houkimebecause if we do
00:31.00houkimesome esds should be actually doubles
00:31.07houkimedoubled
00:31.42Joerg-Neo900http://susepaste.org/35332748  https://www.we-online.de/web/en/leiterplatten/webinare/archiv/microvia_hdi_webinar/teil_ii_1/webinar_archiv_18.php
00:32.25Joerg-Neo900houkime: nope, B2B are always between PCBs and thus I consider then sufficiently "shielded"
00:32.35Joerg-Neo900them*
00:33.19houkimeyes, but it is a tinkerphone. user WILL disassemble it
00:33.30houkimeand if he does, ZAP
00:33.56houkimecan ruin everything
00:35.43houkimeThis is sort of reliability scenarios that haunt me.
00:45.11Joerg-Neo900when user disassembles the device, the B2B are still reasonably protected by mere sequencing of signals in connector. We can't take care to make a disassembled device as robust against environment hazard incl massive ESD as the assembled device
00:47.19Joerg-Neo900nice http://susepaste.org/60071649
00:52.00Joerg-Neo900then we also have level shifters on many of the signals
00:54.32Joerg-Neo900what bothers me most is actually the OTG-USB (pogopins)
00:54.56houkimetests are needed for pogos
00:55.06houkimedo a small testboard
00:55.20houkimeyou can't probably tell otherwise
00:55.31Joerg-Neo900ESD is very hard to test
00:56.52Joerg-Neo900actually I think usually nobody tests it, unless it's MIL standard or somesuch
00:57.17Joerg-Neo900you do your best during design and then trust in what you did
00:57.35houkimeESD maybe not, but the whole concept of usb pogos in terms of signal integruty.
00:57.43Joerg-Neo900maybe run a few zap tests against the complete device
00:58.04houkimeif they fail signal integruity no esd tests on pogos are needed.
00:58.23houkime*integrity
00:58.47Joerg-Neo900when HB USB signal integrity doesn't pan out for USB2.0, we simply rate it USB1.1 only, unless we can fix some issue after proto-v2
00:59.34Joerg-Neo900proto_v2 is exactly to test all this. And to show off something tangible
01:00.16Joerg-Neo900we won't do single-item tests for every detail, it's too expensive
01:00.22houkimeproto_v2 doesn't include pogos.
01:00.30houkimeIt is in your documents
01:00.31Joerg-Neo900err?
01:00.53Joerg-Neo900you lost me
01:01.13Joerg-Neo900prot_v2 definitely includes hackerbus
01:01.25houkimeit includes hackerbus
01:02.21houkimeBut it doesn't include usb for hackerbus
01:02.39houkimelet me recheck this]
01:02.48Joerg-Neo900and we will use a tiny pcb with two pogopins and a USB cable soldered to them, to test HB USB in proto_v2
01:04.11Joerg-Neo900then we'll see if USB2.0 flies or not
01:06.32Joerg-Neo900maybe we talk different topics? there are actually TWO usb channels available on HB: the  OTG and a dedicated one
01:08.04Joerg-Neo900the latter one is subject to feasibility, it needs quite a few additional BOM
01:10.08Joerg-Neo900don't worry about such stuff yet, it's a nice topic to work on when the huge majority of design is finalized
01:10.43houkimei guess i know what's going on
01:10.51houkimerechecking the schematics
01:11.12houkimewait a sec
01:13.55houkimeoh, ok. they are actually included as testpoints
01:13.57houkimeok
01:14.05Joerg-Neo900you got USB_HB_DP/M  and OTG_DP/M
01:14.06*** join/#neo900 Kabouik- (~kabouik@236.34.200.37.customer.cdi.no)
01:14.43Joerg-Neo900the latter as "testpoints" though they actually are pogopin landing pads
01:15.53Joerg-Neo900http://susepaste.org/32537385
01:18.38houkimethey are huge though
01:19.00houkimeeven if i just connect them as stubs (unconnected)
01:19.28houkimethey can detriment signal integrity
01:19.42houkimeon the LOWER side of D pair
01:21.04Joerg-Neo900sorry, you lost me. What's huge?
01:21.14houkimelanding pads
01:21.17houkimethey are huge
01:21.26houkimeand they are conductive
01:21.42Joerg-Neo900not larger than the average solder joint in a USB-A jack
01:22.23Joerg-Neo900please don't worry about such stuff right now too much
01:27.12Joerg-Neo900USB specs say 90 Ohm differential impedance +-15% is completely ok for cables *up to 5m*
01:29.27Joerg-Neo900and watching a standard through-hole USB-A (or -B) receptacle, you'll notice that it's almost impossible to layout impedance matched traces that connect to the pins of those, so small discontinuities are perfectly ok too
01:32.03houkimeI know about acceptability of small discontinuities. I just think bout how to connect these things in parralel to a pair, about echoes and such.
01:34.28houkimethey are a low frequency resonator
01:34.32houkimebasically
01:35.56Joerg-Neo900a pad of less than 2mm diameter is no low freq resonator
01:38.31houkimegonna check freqs of USB 3 and compare to characteristic freqs of this stuff.
01:38.38houkimejust to be safe
01:38.59Joerg-Neo900the two pads are 5.8mm apart from edge to edge, I suggest running the tuned pair through the center between then and add two ~2mm stub traces from the pair to the two pads
01:39.12Joerg-Neo900we have no USB3
01:40.26Joerg-Neo900we also could move the two pogo pads closer together, I guess the center distance of 7.6mm been picked rather arbitrarily
01:42.48Joerg-Neo900btw N900 has a ZSB D+/- testpad pair in battery bay - no idea of the layout for that
01:42.52Joerg-Neo900USB*
01:43.35Joerg-Neo900basically I just moved those testpads from battery bay to HB
01:49.54Joerg-Neo900if you feel like, you may move the pogo landing pad that's closer to case edge towards the other pad, away from case adge. Keep in mind however that user needs to solder the pogopins to a PCB and they need a certain distance between their possibly large footprints
01:51.25houkimepossible pogo places are determined by BOB--lower connectors now
01:51.36Joerg-Neo900seems the one we used for reference has a diameter of 1.83mm
01:52.27Joerg-Neo900http://susepaste.org/64494183
01:54.12Joerg-Neo900so you can't reasonably move them closer together than maybe 2.2mm
01:54.42Joerg-Neo900feel free to do that, if you see need and opportunity for it
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02:51.27houkimegonna sleep.
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09:23.31enycJoerg-Neo900: i note, the usb-testpads in the battery-bay, seemingly bypass the l/c/whatever protection/etc  circuitry under one of the tin-cans nearer the usb-socket...
09:23.39enyc[on n900]
09:24.20enycI have n900 with replaced usb connector, usb was working at some point, not worked in ages ...  someday i'll take apart and investigate agin...  been changing batteries in external charger etc.
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10:02.47enychoukime: that was a short sleep??
10:03.31houkimenormal one.
10:03.42houkime7 hours all ok
10:03.53houkimewell maybe 6 hrs
10:03.59houkimeanyway it worked
10:05.31houkimedreamed about some strange things though. Teleporters, hybernation chambers and amphibian schoolbuses.
10:06.25houkimeand now a connector is at 19 degrees and I think it strikes the balance
10:06.55houkime(well not really, it is just that you can't really plug it other way)
10:07.44bencohhuhu
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12:15.39houkimenope, you can't run a D pair between pogos. pogos are too close to the edge and D pair just won't fit when run between the edge and a pogo
12:16.34houkimeoh
12:16.48houkimethat'ts not what you meant
12:17.39houkimeyou wanna do symmetrical as it seems
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