dos1 | houkime: "cloning from https://neo900.org/git/ee-full/ returns a pack index error" there's a mirror at https://gitlab.com/neo900 | 15:54 |
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houkime | dos1, thanks | 15:55 |
dos1 | norly: ^^^ | 15:55 |
dos1 | I'll try to take a look at what's wrong with the neo900.org repo, but not sure yet when | 15:57 |
houkime | a bit sad that my branch is actually the most recent. | 15:59 |
houkime | nobody worked on neo900 after me it seems. | 15:59 |
houkime | (in ee-full i mean) | 16:00 |
norly | thanks guys | 16:01 |
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 | 18:33 |
houkime | and fo 500 MHz (Neo900/N900 CSI) I can't really think of a way the exact placement could make a significant difference | 18:34 |
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. | 18:40 |
houkime | *mode chokes. | 18:42 |
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. | 18:44 |
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. | 18:46 |
houkime | that said, noise can have a higher frequency than 500 MHz | 18:48 |
houkime | DocScrutinizer05, ^^^^ | 19:47 |
DocScrutinizer05 | depends on particular design | 19:50 |
DocScrutinizer05 | There must be the repos which our last layouter created | 19:51 |
houkime | DocScrutinizer05, I am speaking about a connection between neo900 front camera (via display connector) and bb-xm | 19:51 |
DocScrutinizer05 | hmmm | 19:52 |
houkime | it wasn't layed out unfortunately neither by me or by metacollin | 19:52 |
DocScrutinizer05 | get a plain ferrite block / bead and place it on top of the diff pair, find the place that works best | 19:52 |
DocScrutinizer05 | for better effect, shield the diff pair with a plane above and below | 19:54 |
houkime | DocScrutinizer05, the schematics specifies the exact part number for a choke. ACM2012H. It was actually the placement i was not sure about. | 19:55 |
houkime | As far as physics and documents i found go, the difference between places should be quite negligible. | 19:56 |
houkime | at least on +- a few cm scale. | 19:57 |
Joerg-Neo900 | check N900 | 19:58 |
Joerg-Neo900 | I guess it's legacy | 19:58 |
houkime | Joerg-Neo900, thanks. Haven't though about just checking original pcb. | 19:59 |
houkime | *thought | 19:59 |
Joerg-Neo900 | the purpose is to block common mode signals from reaching chip inputs. Noixe gets picked up on long traces | 19:59 |
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) | 20:02 |
houkime | and in schematics there is only one CMF per differential lane and not 2. | 20:03 |
houkime | the question is then - does N900 frontal camera has a CMF of its own? | 20:04 |
houkime | if it does and if there is also a CMF on bb-xm then CMF on neo900 itself shouldn't be needed. | 20:04 |
houkime | however, i doubt that any of the ends actually has CMFs | 20:05 |
houkime | pins on bb-xm connector which are carrying differential signals for CSI were chosen on an unclear principle. | 20:06 |
DocScrutinizer05 | only one needed when signal direction unidir | 20:12 |
DocScrutinizer05 | the pins prolly where chosen for their function | 20:13 |
houkime | which is... based on bb-xm docs, DVI? And also one stray pin which is on another connector entirely. | 20:14 |
houkime | though there might be some multiplexor magic going on... | 20:16 |
houkime | however mux magic is unlikely to create and destroy CMFs on bb-xm. | 20:17 |
houkime | So, if unidir, then logically CMF should be near a receiver. | 20:19 |
houkime | And there are 2 data lanes in CSI. | 20:19 |
houkime | I don't however know how exactly they are directed. | 20:20 |
houkime | they might be both from camera to bb-xm, or one to camera and one to bb=xm | 20:20 |
houkime | clock-wise, one can suppose that bb-xm is master. | 20:21 |
houkime | so for clock lane camera is a receiver. | 20:22 |
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. | 20:27 |
houkime | hmm... or not if not only CSI is present. need to check. | 20:29 |
houkime | it seems like there is only CSI, one extra external clock signal (for some reason), 2 powerlines and a shutdown signal. | 20:34 |
houkime | found the front camera model ST Microelectronics VS6555. | 20:38 |
houkime | https://www.st.com/stonline/products/promlit/pdf/flstv09860208.pdf datasheet for it however returns an error 404 | 20:41 |
houkime | but this works | 20:43 |
houkime | http://www.natisbad.org/N900/ref/VS6555.pdf | 20:43 |
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. | 20:56 |
houkime | *CCP2.0 | 20:57 |
houkime | CCI which is used for commands is 1 data pin and one clock pin. And that's it. | 21:08 |
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. | 21:10 |
houkime | Joerg-Neo900, i couldn't find based in what data the pinout of the neo900 display connector was established. | 21:11 |
houkime | *based on what data | 21:11 |
houkime | i found in neo900 feasibility study that "cdp" interface is used by the panel also. (2 lanes + SPI) | 21:15 |
DocScrutinizer05 | I think this is covered in out proto-v2 whitepaper. Or ask wpwrak | 21:15 |
houkime | DocScrutinizer05, v2 says nothing about front camera, i checked | 21:16 |
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 | 21:16 |
DocScrutinizer05 | Neo900 mimics a N900, so the pins on BB-xM are same as on N900 | 21:17 |
DocScrutinizer05 | and yes, I think this is covered in v2 whitepaper | 21:18 |
DocScrutinizer05 | more generically as I just paraphrased | 21:19 |
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. | 21:48 |
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