Screen just flashes between RGBW

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nicholas-c
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Screen just flashes between RGBW

Post by nicholas-c » Mon Apr 08, 2019 1:10 pm

Hey! First up, @kite - Wonderful board... love it so much! Makes a build so much easier... Thanks!

Secondly... I've got the Kite Circuit Sword Lite, with a Raspberry Pi Zero, been doing bits to the case etc over the last week or two...

Finally got to the good stuff of the electronics... I installed the Pi Zero onto the circuit sword, some questionable soldering aside, it was working absolutely fine, powers on, booted, I've even transferred some ROM's onto it and done some tests of intro screens etc. Great! Even connected to WiFi etc

However, yesterday, I SFTP'd some ROM's across, called it quits, and today my plastic switch for the case arrived, so it was time to get the switch/mode button glued in.

So with my trusty glue gun I've managed to get the switch glued in, then... Opps? Plugged it all back in, and the screen just cycles between a white/red/green and blue screen (see video for what I mean by cycling the screens). The config-cs.txt is set to normal mode, and I can SSH/SFTP to the Pi itself, so that suggests to me that there isn't anything wrong per say?

[youtube]https://youtu.be/4gbtZY_5vyo[/youtube]

There's no where the switch unit could be shorting I don't think, and I've disconnected the small ribbon cable from the board, and held the power button on the board and the same result happens... This again leads me to think it's not actually related to power switch being installed itself?

Any tips onto what to try would be great, it's kind of stopped me in my tracks!
Last edited by nicholas-c on Thu Apr 11, 2019 6:55 am, edited 1 time in total.

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kite
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Re: Screen just flashes between RGBW

Post by kite » Tue Apr 09, 2019 9:07 am

Check the LCD connector for debris, and check the LCD FPC and clean it.

Second, it's likely one of the signal lines not soldered :) you may find pressing the Pi affects it?

Re work the LIGHT GREEN highlighted pins in the pic below. NOTE that this picture is looking at the BOTTOM of the board. Also note how just under the LCD connector are 4x little test pads? They correspond to the 4 highlighted pins (not in that same order, but some probing will get you the ordering)
Screenshot from 2019-04-09 16-04-53.png
Screenshot from 2019-04-09 16-04-53.png (16.3 KiB) Viewed 571 times

nicholas-c
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Re: Screen just flashes between RGBW

Post by nicholas-c » Tue Apr 09, 2019 2:28 pm

Thanks for the quick reply Kite, much appreciated.

Got the multi-meter out and tested all 4 highlighted pins from the Pi to the test pads (touched end of the pins on the pi, not the board) and all buzz positive on the continuity test. That says to me it’s not the soldering connections?

Inspecting the ribbon cable of the screen I have noticed this...
5028BF14-835F-4513-A2C6-CE3F66E4B525.jpeg
5028BF14-835F-4513-A2C6-CE3F66E4B525.jpeg (2.4 MiB) Viewed 560 times
FADA0398-FD32-450F-B337-665C44221A46.jpeg
FADA0398-FD32-450F-B337-665C44221A46.jpeg (2.43 MiB) Viewed 560 times
It looks like when test fitting, I’ve pushed down too hard and a pin from the pi has squeezed it slightly perhaps?

Would this cause this issue? I’d assume it would simply just not work!

Would you recommend purchasing a new LQ035NC111? (https://www.amazon.co.uk/Hilitand-3-5in ... 07J1H1MYT/ Will this one do the trick?)

Thanks again!
Nick

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Re: Screen just flashes between RGBW

Post by kite » Wed Apr 10, 2019 1:35 am

From the pictures it doesn't look to have pierced the FPC, just dented it, if you wiggled or pressed that area and suddenly it came to full life then that would show it being that, but from inital looking it looks alright.

I would re-work those pins a tiny bit first anyway, on the Pi side of the board (the pin may well be connected to the main board as you have shown with continuity, but it might not actually be fully soldered to the PI itself, which is pretty hard to actually test.. so best to add some fresh solder and re-heat those pads a little)

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Re: Screen just flashes between RGBW

Post by nicholas-c » Wed Apr 10, 2019 3:22 pm

Hey Kite,

So I’ve cleaned up my soldering on some of the GPIO pins, I did buy the zero with the header presoldered to save myself half the soldering job.

However after that, same continuity tests are fine on the test pads (tested from both sides of the pi if that makes any difference) and screen does the same issue of cycling through the coloured states.

Not sure what to try now at all!

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Re: Screen just flashes between RGBW

Post by kite » Thu Apr 11, 2019 4:16 am

Hm ok, i'm not really too sure to be honest, it might be best to send to me with the screen and I'll find out what's wrong. It could be the LCD screen but it might end up being a waste of time just sending it out if it isn't that! Could you send me an email and i'll give you the details and we'll sort it out

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Strider
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Re: Screen just flashes between RGBW

Post by Strider » Thu Apr 11, 2019 6:22 am

Have you tried reflashing a fresh image? I had to hard reboot a Gameboy Zero last night and everything worked just fine until I tried playing a game. SSH to back up my saves, install a new image, and everything is fine now.

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Re: Screen just flashes between RGBW

Post by nicholas-c » Thu Apr 11, 2019 6:55 am

Wiped the card and flashed a brand new image on it the other day (Had no save games or anything to lose anyway) and no luck whatsoever :(

Thanks for the suggestion though

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Re: Screen just flashes between RGBW

Post by Strider » Thu Apr 11, 2019 4:46 pm

Okay, sorry! I figured you'd tried it but sometimes I have a hard time with the obvious "turn it off and back on again" kind of fixes so it's worth mentioning.

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Re: Screen just flashes between RGBW

Post by rankar » Sun Apr 14, 2019 10:45 pm

it's the ribbon cable. those things are so sensitive that a detent in the ribbon will produce bizarre results. i would replace the ribbon cable.

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