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| 00:17.25 | *** 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 http://maemo.cloud-7.de/irclogs/freenode/_neo900/ & http://irclog.whitequark.org/neo900 | Latest news: http://neo900.org/news/joerg-pia-2018-03-01 |
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| 13:54.57 | dos1 | houkime: "cloning from https://neo900.org/git/ee-full/ returns a pack index error" there's a mirror at https://gitlab.com/neo900 |
| 13:55.24 | houkime | dos1, thanks |
| 13:55.57 | dos1 | norly: ^^^ |
| 13:57.51 | dos1 | I'll try to take a look at what's wrong with the neo900.org repo, but not sure yet when |
| 13:59.31 | houkime | a bit sad that my branch is actually the most recent. |
| 13:59.47 | houkime | nobody worked on neo900 after me it seems. |
| 14:00.56 | houkime | (in ee-full i mean) |
| 14:01.41 | norly | thanks guys |
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| 16:33.51 | houkime | trying to figure out where to best place a common mode choke on a differential pair which then goes through a connector and through a cable |
| 16:34.52 | houkime | and fo 500 MHz (Neo900/N900 CSI) I can't really think of a way the exact placement could make a significant difference |
| 16:40.27 | houkime | Joerg-Neo900, do you know of any particular design considerations for that? I searched for several hours today and learned a lot of new things about differential pairs but couldn't really find an answer for placement of common node chokes. |
| 16:42.42 | houkime | *mode chokes. |
| 16:44.32 | houkime | STI filters application notes for example just say to place them on the both sides of the cable somewhere between a connector and an IC but that's it. |
| 16:46.31 | houkime | physics-wise, 500 Mhz has a wavelength of 60 cm and even if we consider an edge to be 10-20 cm it is very huge. |
| 16:48.20 | houkime | that said, noise can have a higher frequency than 500 MHz |
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| 17:47.20 | houkime | DocScrutinizer05, ^^^^ |
| 17:50.14 | DocScrutinizer05 | depends on particular design |
| 17:51.04 | DocScrutinizer05 | There must be the repos which our last layouter created |
| 17:51.27 | houkime | DocScrutinizer05, I am speaking about a connection between neo900 front camera (via display connector) and bb-xm |
| 17:52.00 | DocScrutinizer05 | hmmm |
| 17:52.29 | houkime | it wasn't layed out unfortunately neither by me or by metacollin |
| 17:52.52 | DocScrutinizer05 | get a plain ferrite block / bead and place it on top of the diff pair, find the place that works best |
| 17:54.00 | DocScrutinizer05 | for better effect, shield the diff pair with a plane above and below |
| 17:55.44 | houkime | DocScrutinizer05, the schematics specifies the exact part number for a choke. ACM2012H. It was actually the placement i was not sure about. |
| 17:56.32 | houkime | As far as physics and documents i found go, the difference between places should be quite negligible. |
| 17:57.41 | houkime | at least on +- a few cm scale. |
| 17:58.26 | Joerg-Neo900 | check N900 |
| 17:58.40 | Joerg-Neo900 | I guess it's legacy |
| 17:59.19 | houkime | Joerg-Neo900, thanks. Haven't though about just checking original pcb. |
| 17:59.24 | houkime | *thought |
| 17:59.24 | Joerg-Neo900 | the purpose is to block common mode signals from reaching chip inputs. Noixe gets picked up on long traces |
| 18:02.14 | houkime | Joerg-Neo900, from this logic the ideal placement is near client ICs on both sides. Thoughin this particular case both clients are not on neo900 (one on bb-xm and one on front panel near display) |
| 18:03.33 | houkime | and in schematics there is only one CMF per differential lane and not 2. |
| 18:04.14 | houkime | the question is then - does N900 frontal camera has a CMF of its own? |
| 18:04.58 | houkime | if it does and if there is also a CMF on bb-xm then CMF on neo900 itself shouldn't be needed. |
| 18:05.23 | houkime | however, i doubt that any of the ends actually has CMFs |
| 18:06.32 | houkime | pins on bb-xm connector which are carrying differential signals for CSI were chosen on an unclear principle. |
| 18:12.22 | DocScrutinizer05 | only one needed when signal direction unidir |
| 18:13.31 | DocScrutinizer05 | the pins prolly where chosen for their function |
| 18:14.39 | houkime | which is... based on bb-xm docs, DVI? And also one stray pin which is on another connector entirely. |
| 18:16.44 | houkime | though there might be some multiplexor magic going on... |
| 18:17.47 | houkime | however mux magic is unlikely to create and destroy CMFs on bb-xm. |
| 18:19.19 | houkime | So, if unidir, then logically CMF should be near a receiver. |
| 18:19.45 | houkime | And there are 2 data lanes in CSI. |
| 18:20.10 | houkime | I don't however know how exactly they are directed. |
| 18:20.50 | houkime | they might be both from camera to bb-xm, or one to camera and one to bb=xm |
| 18:21.27 | houkime | clock-wise, one can suppose that bb-xm is master. |
| 18:22.10 | houkime | so for clock lane camera is a receiver. |
| 18:27.14 | houkime | however, in the first scenario where camera has 2 lines to bb-xm it becomes uncontrollable and can operate only in some default mode. |
| 18:29.38 | houkime | hmm... or not if not only CSI is present. need to check. |
| 18:34.39 | houkime | it seems like there is only CSI, one extra external clock signal (for some reason), 2 powerlines and a shutdown signal. |
| 18:38.25 | houkime | found the front camera model ST Microelectronics VS6555. |
| 18:41.01 | houkime | https://www.st.com/stonline/products/promlit/pdf/flstv09860208.pdf datasheet for it however returns an error 404 |
| 18:43.26 | houkime | but this works |
| 18:43.28 | houkime | http://www.natisbad.org/N900/ref/VS6555.pdf |
| 18:56.47 | houkime | aaand it has nothing to do with csi whatsoever. It uses some cryptic CCP 2.- for data which is one clock diff. lane and one data lane. |
| 18:57.04 | houkime | *CCP2.0 |
| 19:08.49 | houkime | CCI which is used for commands is 1 data pin and one clock pin. And that's it. |
| 19:10.53 | houkime | Perhaps ccp was wrongly identified as CSI on the display connector, but then there is a question: for whom is the second dataline and if it even exists. |
| 19:11.39 | houkime | Joerg-Neo900, i couldn't find based in what data the pinout of the neo900 display connector was established. |
| 19:11.49 | houkime | *based on what data |
| 19:15.08 | houkime | i found in neo900 feasibility study that "cdp" interface is used by the panel also. (2 lanes + SPI) |
| 19:15.24 | DocScrutinizer05 | I think this is covered in out proto-v2 whitepaper. Or ask wpwrak |
| 19:16.09 | houkime | DocScrutinizer05, v2 says nothing about front camera, i checked |
| 19:16.47 | DocScrutinizer05 | I'm really sorry I tried to keeep ALL this in my mind for over 5 yeras. At one point in time some headcrash and trash collection happened |
| 19:17.49 | DocScrutinizer05 | Neo900 mimics a N900, so the pins on BB-xM are same as on N900 |
| 19:18.32 | DocScrutinizer05 | and yes, I think this is covered in v2 whitepaper |
| 19:19.06 | DocScrutinizer05 | more generically as I just paraphrased |
| 19:48.05 | houkime | I have checked original N900 board. All 3 CMFs are grouped right near display connector. However it doesn't seem to have any ESD protection which neo900 schematic calls for. |
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