Right half of display garbled

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mypen
Posts: 3
Joined: Wed Jan 06, 2016 5:13 am

Right half of display garbled

Post by mypen »

The right half of my display is garbled.
The left half seems to function properly.

The rows appear to be offset by about 5 rows (shifted up) and there are a lot of pixels that do not clear.
The columns do appear to occasionally wander towards the left by a couple of columns before resetting back to their proper home position.

I have double-checked all solder connections and everything appears to be good.

It passes all power tests, and the buttons function normally, and the contrast adjusts correctly, it just has this one problem.

I just soldered this together last weekend and the display has been like this since I first turned it on.
20160105_150023.jpg
jye1
Posts: 1227
Joined: Wed Feb 20, 2013 4:58 pm

Re: Right half of display garbled

Post by jye1 »

Please double check the signal LCD_CS1 and LCD_CS2 at all connections including the pin pads at MCU. These two signals are the chip selects for the two LCD controllers on LCD module. Each of the controllers takes care of half the screen.
mypen
Posts: 3
Joined: Wed Jan 06, 2016 5:13 am

Re: Right half of display garbled

Post by mypen »

Thank you very much for your help.

CS1 measures 0.8V, CS2 measures 0.5V. I suspect these are averages because they are most likely switching on and off very fast, yes?

If CS2 was not getting turned on, I would expect to see no intelligence on it but I can see the data that should be on the far right of the screen but it is offset vertically and there are several pixels that are turned on that should not be.
The data that is visible does change with the different screens that get displayed so it is live, valid data.

I don't know if the problem is in the LCD or the controller chip on the main board and would like to narrow it down so I can replace the correct component.

I suspect that the problem is most likely in the LCD because one half of the display does function properly and the only difference between the two halves is which chip select is enabled so if the problem was the controller IC, I would expect to see this on both halves. Does this sound reasonable?
mypen
Posts: 3
Joined: Wed Jan 06, 2016 5:13 am

Re: Right half of display garbled

Post by mypen »

I measured CS1 and CS2 with a scope and found that the voltage on CS2 is about half of CS1 with occasional spikes to full voltage:
CS1.png
CS1.png (6.81 KiB) Viewed 12624 times
CS2.png
CS2.png (6.46 KiB) Viewed 12624 times
jye1
Posts: 1227
Joined: Wed Feb 20, 2013 4:58 pm

Re: Right half of display garbled

Post by jye1 »

CS2 looks abnormal. Please probe right on pin34 of U4 and pin16 of LCD module to see if they have any difference. Re-touch U4 pin34 with iron to make sure there is no cold joint.
Alexaz
Posts: 2
Joined: Sat May 21, 2016 6:27 pm

Re: Right half of display garbled

Post by Alexaz »

I've got a similar problem, but in my case the right side (CS2) of the display turns garbled for a couple of seconds on boot time, then it turns blank (nothing on beautiful greem right side display). The left side (CS1) of the display functions OK. It looks like the problem above was not resolved (or was it?). Any ideas, suggesions, versions, or proposals?
jye1
Posts: 1227
Joined: Wed Feb 20, 2013 4:58 pm

Re: Right half of display garbled

Post by jye1 »

It is suggested to check conductivity of CS1 and CS2 right from the MCU pins to the LCD. There may by poor connection or shorts. If the connections are good it could be LCD internal issue.
Alexaz
Posts: 2
Joined: Sat May 21, 2016 6:27 pm

Re: Right half of display garbled

Post by Alexaz »

jye1 wrote:It is suggested to check conductivity of CS1 and CS2 right from the MCU pins to the LCD. There may by poor connection or shorts. If the connections are good it could be LCD internal issue.
Yep, jye1, I was just going to double check most critical points. It looks like timing and CS1 are OK (a rough check on CS2 also looks fine). In case I end up in LCD replacement that would not be a big problem. I've already checked availability of similar LCD's on the market. OK, I cross my fingers and start digging into the PCB. Let's have some more fun. =)
rahe55
Posts: 15
Joined: Mon Apr 30, 2018 2:12 pm

Re: Right half of display garbled

Post by rahe55 »

Interesting thread - since I am still struggling with my LCD Display- see thread disturbed LCD display - was the issue solved - how - ? Also pictures in this thread gone.
Any additional docs on the LCD - how it is controlled - a pdf on the internal workings - could not find it anywhere ?
Is there something like a character mode and a byte - mode ?

Still keen to learn

Ralf 8-)
jye1
Posts: 1227
Joined: Wed Feb 20, 2013 4:58 pm

Re: Right half of display garbled

Post by jye1 »

This is the datasheet for the LCD -- https://jyetech.com/Products/Accessorie ... 64D-04.pdf

The controller for inside the LCD module is S6B0108. You might need to look at its datasheet (you can search the net to find its datasheet) if you want to know more about how to use the LCD.
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