libera/#neo900/ Thursday, 2019-08-08

houkimeJoerg-Neo900, on the display connector, pins 39-31 am i correct to assume that it is backlight LED array?16:50
Joerg-Neo900sorry, I don't know off top of my head. Maybe refer to original N900 schematics16:51
houkimeJoerg-Neo900, is it avalable even?16:52
Joerg-Neo900of course16:52
Joerg-Neo900 is a block diagram, you need to google for the schematics16:53
houkimefetched RX-51 chematics from plan916:56
houkimeyep it is backlight16:57
Joerg-Neo900houkime: please check docs/hw/Nokia_N900_RX-51_Schematics.pdf et al...  in  and NEVER EVER post the concatenated URL so spiders could start searching it! If this happens, the URL vanishes in no time17:00
Joerg-Neo900you can search dirs up to docs/17:01
Joerg-Neo900all of this stuff is (or was) publicly available, but I collected it for convenience reasons17:11
houkimereplacing D1902 (zener in backlight regulation) with BZX88418:52
houkime(it needs to be able to regulate either on the 10.5v level or 21v level)18:53
houkimedepending on serial or parallel connection of backlight LED rows18:53
houkimeBZX884 series contains parts for both voltages with the same footprint18:54
houkimeit is also new (2018) and small18:54
houkimeprevious zener there was misrated and too weak.18:55
Joerg-Neo900>><houkime> BZX884 series contains parts for both voltages with the same footprint<< :thumbsup:19:52
Joerg-Neo900>>too weak<< it only triggers a shutdown, doesn't regulate by itself19:53
Joerg-Neo900actually which Zener?19:58
Joerg-Neo900got it added post ?20:00
Joerg-Neo900I'd really feel less nervous if I knew exactly what schematics you're working from20:01
houkimethis one is from official neo900 schematics, D1902 is present on the master branch as far as i remember20:03
Joerg-Neo900  latest in my local git branch20:03
Joerg-Neo900no idea what's going on20:04
houkimeneed to recheck20:04
Joerg-Neo900don't get me wrong, probably a Zener is an excellent idea (if applied correctly frpm P1901G 31 to 29) but why don't I see it?20:08
Joerg-Neo900ugh wait, not this way20:09
Joerg-Neo900this sucks, the original design doesn't allow for a zener20:10
Joerg-Neo900you'd need a 10k or somesuch (instead trace) from R1915 to R1906, then Zener to R190620:12
houkimeinteresting. I rechecked. This realy isn't in master20:13
Joerg-Neo900so Zener pulls up FB without using up full current meant for backlight#20:13
houkimeWill need to investigate how this happened20:13
Joerg-Neo900that's what eeshow is for20:14
Joerg-Neo900just bisect while watching the index sheet until a change on sheet 19 is shown by yellow mark of sheet19 on index sheet20:18
Joerg-Neo900alas it seems it's borked for me now20:19
houkimethis is how itlooks on my end
houkimeok, will try to bisect20:19
Joerg-Neo900zhere's a R1917 which I just "invented" :-D20:20
houkimeit is actually how i found it in regulator datasheet as one of the applications so it wasn't looking suspicious for me.20:21
Joerg-Neo900looks good but I have no idea who and when designed this20:21
Joerg-Neo900DNP comment oon R1912 and 1914 missing20:23
Joerg-Neo900aaa nope, all fine20:26
Joerg-Neo900they are "[   serial]"20:26
Joerg-Neo900bug: R1917 1k to allow Zener to pull ip FB20:28
Joerg-Neo900check if that complies with FB impedance20:29
Joerg-Neo900if needed, make it 100R20:29
Joerg-Neo900rationale: when user operates device without display connected, avoid overvoltage from missing feedback to FB. But also avoid Zener and R1916 consuming the full power (10V * 40mA?) usually consumed by display backlight20:36
Joerg-Neo900it's actually *possible* that Metacollin discussed this with me and added the Zener20:50
Joerg-Neo900...and I forgot20:50
Joerg-Neo900houkime: did I already thank you for the great work?20:53
Joerg-Neo900a pity it can't help the project anymore20:54
houkimei don't think the life of the project has anything to do with what you or me think about the current status.20:57
houkimeit is opensource now completely.20:57
houkimepeople decide what to do with it20:57
houkimei make these changes now for people20:58
houkimein the end, after i am done with it, i can just eliminate N900 compatibility requirement, design a case in a freecad, replace display and retune tracks for new antennas and it will be good to go regardless of part sourcing.21:02
houkimeforgot to correctly place a slide sensor on the UPPER... oops.21:56
houkimeluckily a transform is already on hand21:56
houkimeplaced and locked22:33
dos1houkime: still got issues with git repos?22:54
houkimedos1, no, it is ok.23:23
houkimedos1, checked right now23:24
houkimeremote is not too verbose but clone does finish after a long while23:24

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