**** BEGIN LOGGING AT Thu May 28 02:59:58 2015
May 28 03:40:37 <ds2> Abhishek_: u got a scope right?
May 28 03:41:10 <ds2> Abhishek_: what frequency is the ripple? does it match the expected boost converter switching freq?
May 28 03:42:12 <ds2> Abhishek_: I can think of 2 things: 1 - the dielectric is derated in your application (what voltage is it rated for and what size) 2. Traces may be a bit think and things are getting inductive (for this case, a ferrite bead)
May 28 03:44:12 <Abhishek_> A bit thin, hmm 0.35mm thick and 400mA current
May 28 03:44:42 <ds2> Abhishek_: what are you driving?
May 28 03:44:48 <ds2> (how many LEDs, and how many chains)
May 28 03:44:49 <Abhishek_> ds2: It doesn't seem to match the boost conv frequency
May 28 03:44:53 <Abhishek_> 3S
May 28 03:45:06 <Abhishek_> 9.5V from 3.3V
May 28 03:45:07 <ds2> ooh... that might be the LCD itself unless it is a harmonic
May 28 03:45:15 <ds2> how many LEDs?
May 28 03:45:50 <Abhishek_> 3 series, don't know exactly the no of parallel chains inside
May 28 03:46:11 <ds2> what LCD?
May 28 03:46:18 <ds2> trying to estimate power draw
May 28 03:46:33 <ds2> also what booster?
May 28 03:46:34 <Abhishek_> Draws approx 400mA
May 28 03:46:42 <Abhishek_> 7inch
May 28 03:46:50 <Abhishek_> SY7201
May 28 03:47:06 <ds2> 400mA @ 3.3V or @ 9.5V?
May 28 03:47:14 <Abhishek_> @3.3V
May 28 03:47:33 <Abhishek_> Backlight current set to 100mA
May 28 03:48:03 <ds2> 100mA!??? seems a bit
May 28 03:48:07 <ds2> high
May 28 03:48:15 <ds2> blah... want me to login... oh well too bad
May 28 03:48:29 <ds2> switch to a TI switcher or some other vendor who won't require logins to get a datasheet
May 28 03:48:30 <ds2> :D
May 28 03:48:46 <Abhishek_> Lemme give you a non login link
May 28 03:49:42 <ds2> what's the specs on your 10uF cer cap?
May 28 03:49:47 <Abhishek_> http://hands.com/~lkcl/eoma/kde_tablet/1388365231-20314.pdf
May 28 03:50:07 <Abhishek_> The cap seems to be 16V X5R
May 28 03:50:39 <ds2> what size? 1206?
May 28 03:50:51 <Abhishek_> 0805
May 28 03:51:13 <ds2> so it'll probally be equiv to like 4uF or so after derating for the DC bias
May 28 03:51:20 <ds2> what freq is the ripple?
May 28 03:52:14 <Abhishek_> It's more like bursts on the 3.3 V rail, some 3Mhz or so
May 28 03:52:29 <ds2> I suspect that might be the LCD during updates
May 28 03:52:42 <ds2> do you have bypassing on the LCD supply? (is this a single supply LCD?)
May 28 03:53:24 <Abhishek_> Nope it needs all AVdd, Vgl, Vgh and Vcom....
May 28 03:53:46 <ds2> oh... do you have decent caps on all the rails?
May 28 03:53:52 <Abhishek_> There's another boost converter and charge pump on that
May 28 03:54:11 <ds2> LCDs can spike during updates with certain patterns
May 28 03:54:51 <ds2> bbl, dinner
May 28 03:55:03 <Abhishek_> ds2: I know those are good because the LCD works with the backlight off
May 28 04:32:33 <ds2> hmmmm
May 28 04:32:56 <ds2> try putting a bit more caps on it
May 28 05:20:35 <Abhishek_> ds2: Would try with a ferrite bead if I am able to get one
May 28 06:52:23 * Abhishek_ orders ferrite beads
May 28 07:15:43 <vvu> morning!
May 28 09:45:30 <Abhishek_> gm
May 28 16:10:02 <moto-timo> buenas
May 28 16:26:36 <nerdboy> moin
May 28 17:06:25 <Abhishek_> gm
May 28 17:06:34 * vvu finsihed his university duties...
May 28 17:07:19 <vvu> now i just need to throw the cap in the air
May 28 17:13:32 <moto-timo> take pictures
May 28 17:59:23 * Abhishek_ has still 2 years to go
May 28 18:21:07 <apaar__>  /me has 3 :P
May 28 18:23:31 <Abhishek_> good
May 28 18:44:25 <Abhishek_> jkridner: Rewired the PCB *fingers crossed* connecting the cape now
May 28 18:44:32 <jkridner> :-)
May 28 18:47:13 <Abhishek_> gah, no luck again
May 28 18:49:10 <ds2> what is it doing and what is your overall problem?
May 28 18:50:44 <Abhishek_> uploading a vid
May 28 18:50:59 <ds2> 'k
May 28 18:51:56 <Abhishek_> moved the boost converters to 5V but still same flicker in display
May 28 18:53:01 <ds2> describe the "flicker"
May 28 18:53:11 <ds2> is the screen also washed out?
May 28 18:54:44 <Abhishek_> uploading 4%
May 28 18:56:35 <ds2> what service?
May 28 18:58:16 <Abhishek_> youtube
May 28 18:59:22 <Abhishek_> 72%
May 28 18:59:56 <ds2> oh that will take a while
May 28 19:00:24 <Abhishek_> 96
May 28 19:01:32 <ds2> is the screen also washed out?
May 28 19:01:49 <Abhishek_> doesn't seem so
May 28 19:02:12 <ds2> can you verify pclk/vsync/hsync are within the specs of the LCD?
May 28 19:02:20 <ds2> also verify the voltages is in spec?
May 28 19:02:25 <Abhishek_> In the video, I am manipulating the backlight, the flicker in the image is what is to be seen
May 28 19:02:27 <Abhishek_> https://www.youtube.com/watch?v=l4XCsC80Qvc&feature=youtu.be
May 28 19:02:31 <Abhishek_> yes, they are
May 28 19:02:37 <ds2> I have had LCDs do odd ball things when timing is off
May 28 19:03:21 <ds2> that is not noise!
May 28 19:03:39 <ds2> check the pclk/vsync/hsync/de signals
May 28 19:03:48 <ds2> one of them is getting messed up
May 28 19:04:00 <Abhishek_> look at 0:00-0:01
May 28 19:04:03 <ds2> s/one/one or more/
May 28 19:04:53 <ds2> vsync would be my guess
May 28 19:04:57 <ds2> also verify the polarity
May 28 19:05:17 <Abhishek_> but when the backlight is off, the screen looks okay and stable under strong light
May 28 19:05:24 <Abhishek_> turning the backlight on messes it up
May 28 19:05:26 <ds2> i tried to step through it and I see the same image rolling as you mess with the backlight
May 28 19:05:57 <ds2> i am suspecting the backlight is inducing the ctrl lines to mess up
May 28 19:06:08 <Abhishek_> yeah
May 28 19:06:23 <ds2> is the backlight on a different flex or the same flex?
May 28 19:06:31 <Abhishek_> on the same flex
May 28 19:06:51 <ds2> did you have all the grounds connected?
May 28 19:07:08 <Abhishek_> yeah, all the grounds are connected
May 28 19:07:25 <Abhishek_> the LED- goes to the boost converter FB
May 28 19:07:43 <ds2> try this then - backlight on, probe VSYNC
May 28 19:07:48 <ds2> see if it stable
May 28 19:07:53 <ds2> probe it at the flex connector
May 28 19:08:01 <ds2> repeat with HSYNC and PCLK and DE
May 28 19:08:31 <Abhishek_> the signals become noisy, I saw it
May 28 19:08:42 <Abhishek_> ds2: https://hackaday.io/project/4410-yet-another-beaglebone-displaycaptouch-cape/log/18530-initial-tests
May 28 19:08:45 <ds2> how noisy? what's the P-P value?
May 28 19:09:43 <ds2> got a scope shot?
May 28 19:09:59 <Abhishek_> nope wasn't able to take
May 28 19:10:11 <Abhishek_> IIRC >1 Vpp spikes on the 3V3 rail
May 28 19:14:30 <ds2> no
May 28 19:14:33 <ds2> not on the 3V3 rail
May 28 19:14:38 <ds2> on the VSYNC line itself
May 28 19:16:32 <Abhishek_> will take them tomorrow
May 28 19:17:55 <ds2> if the noise on the VSYNC line is strong enough, it can cause the LCD to think VSYNC occurred at other times then intended
May 28 19:18:06 <ds2> do you have a current limited power supply?
May 28 19:18:41 <ds2> if - set the current limit to something sane like 0.020mA (verify with a DMM)
May 28 19:18:46 <ds2> oops 0.020A
May 28 19:18:55 <ds2> then use that to drive the backlight instead of the switcher
May 28 19:19:13 <ds2> verify it is working that way
May 28 19:19:34 <ds2> FWIW - I have had 0 luck with the asian parts
May 28 19:20:00 <ds2> less waste of a time with On/TI/LTC stuff
May 28 19:42:13 * Abhishek_ is running out of ideas
May 28 19:43:12 <ds2> exonerate or prove the switcher is guilty first
May 28 19:43:30 <ds2> it could be the output is somehow getting transfered to the signals inside the LCD
May 28 19:45:08 <Abhishek_> turns out that if I put my hand on the EN of the boost converter, the backlight glows dim and I am able to see the display stable
May 28 19:45:19 <Abhishek_> *finger
May 28 19:45:30 <ds2> how odd
May 28 19:45:44 <ds2> is the output of the switcher also using the same 10uF/16V cap?
May 28 19:46:03 <Abhishek_> it is, but it would obviously be derated
May 28 19:46:16 <ds2> wonder if putting more cap on there would help
May 28 19:46:43 <ds2> got some tantalums handle to parallel it in?
May 28 19:47:32 <Abhishek_> have one, but not sure of the voltage rating
May 28 19:47:48 <Abhishek_> might be a 6.3V one
May 28 19:49:28 <ds2> that won't help
May 28 19:49:35 <ds2> what about alum elec?
May 28 19:50:33 <Abhishek_> okay found a 10uf Al
May 28 19:50:49 <ds2> parellel it in (keep the leads short)
May 28 19:50:53 <ds2> see if it helps
May 28 19:50:56 <ds2> bbl - lunch
May 28 20:04:24 <Abhishek_> should I change the inductor and try?
May 28 21:54:27 <ds2> \
May 28 21:54:48 <ds2> why change the inductor?
May 28 21:54:49 <Abhishek_> nm
May 29 01:34:17 <mani_> Hi,I want to work on IIO  debugging  tool.  where to start from? I have some experience in kernel programming.
May 29 02:09:08 <ds2> @#%!@#@#!@##$@$@##@!#!@ Amazon EC2 is infested with spammers
May 29 02:09:41 <rcn-ee> it's probally "cheaper" then trying to 'hack into' a server. ;)
**** ENDING LOGGING AT Fri May 29 02:59:59 2015