flickering display when running Lejos

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flickering display when running Lejos

Postby pthor » Thu Jul 29, 2010 11:46 pm

When running the nxt firmware v1.05 the display works fine. When I load Lejos, I can sometimes see the Lejos logo and the menu, but it will always disappear. Sometimes the display will flicker.

Is this the capacitor problem, even though it works fine with nxt firmware?

Thanks
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Re: flickering display when running Lejos

Postby Shawn » Fri Jul 30, 2010 10:11 pm

pthor wrote:When running the nxt firmware v1.05 the display works fine. When I load Lejos, I can sometimes see the Lejos logo and the menu, but it will always disappear. Sometimes the display will flicker.

Is this the capacitor problem, even though it works fine with nxt firmware?


Good question. I suffered flickering for a while but now it's gone completely. I don't run nxt firmware though so can't compare.

When was the last time you ran the nxt firmware. I mean maybe your brick just degraded (the capacitor connection worsened) since the last time you ran the nxt firmware.

Like right now if you put the nxt firmware on, it works but if it's leJOS it doesn't. That's kinda what you said but I just want to confirm this.

Shawn
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Postby gloomyandy » Sat Jul 31, 2010 8:43 am

Hi,
This is a strange one. leJOS uses the same basic mechanism to write to the LCD screen as used by the Lego firmware (basically a DMA write). So it is hard to see why one would flicker and not the other. The only thing I can think of is that the update frequencies may be slightly different and that this could have some sort of impact...

Andy
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Postby Shawn » Sat Jul 31, 2010 9:45 am

gloomyandy wrote:
This is a strange one.


Speaking of strange. Mine works completely fine now. I think I left it in the hot sun today.

I changed batteries after the screen went out a couple of day ago, but it was just blank.

Now after being in the sun, (with those same batteries) it works fine.

Well nxjbrowse never failed so I don't have plans to get the soldering iron immediately even if it goes again.
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Re: flickering display when running Lejos

Postby skoehler » Sat Jul 31, 2010 9:48 am

pthor wrote:When running the nxt firmware v1.05 the display works fine. When I load Lejos, I can sometimes see the Lejos logo and the menu, but it will always disappear. Sometimes the display will flicker.

Is this the capacitor problem, even though it works fine with nxt firmware?

Thanks


Is it possible for you to make a video of the flickering?
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Re: flickering display when running Lejos

Postby Shawn » Sat Jul 31, 2010 1:22 pm

skoehler wrote:
Is it possible for you to make a video of the flickering?


Your are asking pthor, but I will just comment that my flickering was very very similar to a video about how to fix the capacitors. They showed the flickering and then soldered the capacitors and then it worked.

I don't know about pthor's case though.
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Postby pthor » Tue Aug 03, 2010 12:52 am

Ok, it is now a few days later, and it flickers really bad even with the NXT firmware. It obviously got worse. Hmm. I just popped the case off and am going to try soldering the capacitor that has been mentioned before.
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Postby Shawn » Fri Aug 20, 2010 11:46 pm

pthor wrote:Ok, it is now a few days later, and it flickers really bad even with the NXT firmware. It obviously got worse. Hmm. I just popped the case off and am going to try soldering the capacitor that has been mentioned before.


Did you do the soldering? Did it work?

I don't understand electronics well but question if it is really only capacitor related. The reason I have this question is that:

1) this morning my screen went almost completely blank with just a little garbage fuzz.

2) I uploaded and ran a program via usb which listened for a bluetooth connection. The screen was completely blank and I couldn't see the usual question I have "Use BT?" which requires a button press to start. I know I need to do that though so just did.

3) My Android handset sent BT commands and the brick displayed what it should. In particular, I used a method like this:

Code: Select all
public static void drawToScreen(String message, int x, int y) {
       LCD.clear();
       LCD.drawString(message, x, y);
       LCD.refresh();
   }


4) the messages displayed perfectly on the NXT screen

5) on program shutdown, the leJOS three-beep splash screen showed and then the menu displayed

6) now my brick is displaying normally again.

I don't have time to test further now but wonder if LCD.drawString(message, x, y); is the root of my problem. I don't understand x, y well and so was putting negative values for y thinking that'll move the message down the screen. That's not the usage though. Anyway, I'm left wonder if my misusage somehow caused the outage. Another possibility is again temperature. It was cool in the morning when I first tried but it was in the sun for a little while before I tried again. Maybe though it is a loose capacitor and my moving it had an effect.
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Postby WalrusBrigade » Tue Jan 18, 2011 7:11 pm

I'be been having a similar issue. The leJOS code is working fine, but the screen is a set of flickering lines. I've tried reflashing the firmware with no effect. I haven't tried returning to the NXT firmware. It has been a while since I have used this brick, so it could be the capacitor thing. Can anyone point me to a tutorial for safely opening the brick and locating the capacitor? Thanks.
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