The long journey towards a working display

EvilDragon

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Well, as you know from yesterday's post, we got the display to work.

However, as promised, we want to be as open and in-depth as possible, so here's an explanation of what we did during the last weeks (well, mostly Nikolaus...)

You will also see some more pictures attached to the post.

Enjoy :)

The following text is directly from Nikolaus (gta04)


5 weeks of treasury hunt have finally lead to a successful "game over". The MIPI interface does no longer woe.

Firstly we did have some hardware bugs (e.g. swapped wires - due to a misprint in a data sheet).
After fixing this we quickly did have a first success: we were able to send some commands and read values back from the display.
But the display stayed dark when sending the initialization sequence.

For some lengthy time we did suspect the OMAP5 and/or Linux drivers and tried to understand/modify/fix/improve it.
But the display stayed dark.

And measuring experiments with an oscilloscope did not show obvious deviations from what we could expect. We were even tempted to rent a better oscilloscope or a commercial MIPI-DSI tester.

Well, it became obvious that our treasure map (data sheet) for the panel was an incomplete excerpt of the data sheet of the controller (it did not have the full command list of the panel). After knocking on many doors, I received a copy of the original treasure map on Tuesday morning :)

It did list all commands and gave a better understanding of everything. But some commands still did not work. I was not even able to read out the chip id code...

Then, I did measure directly on the panel to verify the voltages to exclude another hardware bug.
The result was interesting: the voltages were in coincidence with the default settings according to the data sheet.
But they were not matching the values that should have been set by sending the initialization sequence to the panel.
So it became clear that for some reason the panel did ignore some (not all) of the commands sent to the panel.

After browsing again and again I suddenly found a small footnote on page 244...

We simply have to send the manufacturer specific commands in a slightly different way (it is roughly comparable to use either TCP vs. UDP).

With this knowledge it was also possible to decrypt one table in the panel data sheet... But that is common for such games - afterwards you know which redundant deviations you have taken...

After fixing our kernel driver it worked almost immediately to read back the correct chip id code. Then, it was only a small final step to enable and see a test pattern.


And even the OMAP5 DSS subsystem was initialized correctly, so there was the Linux Tux and some xterm.

If I look at the photos I must say that I am really impressed. Seeing a full web page in a readable manner is amazing.

So let's take the next challenging treasure hunt :)
 

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Grench

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VERY cool!

Thanks for the update - I'm glad that issue has been knocked down.

Keep the updates coming - we're all looking forward to them!
 

rSl

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wow! the screen looks really awesome!!!


thanks for the nice update!


:)
 

rand

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Pyra Development process 35% complete . . .

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levi

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I like how the backlight of the display makes it look a little like it's casting its own halo. We are not worthy, etc. etc. !


Still a long way short of 35% though. This is only getting an OS running on a dev board, essentially. We've still seen nothing of the case, or a real board, and there's still plenty of software work to be done. Very exciting development though, for sure!
 

szr

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Huge kudos. It's like watching a new life spring forth into existence :)
 

xiongxioi

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The screen looks rather pretty, good work, ED and GTA4.

So, is the type of touch screen technology decided yet? I did not see any touch screen parts.
 

Exophase

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Good stuff, thanks for the continued updates.

ED, you have a really high frame rate camera, right? Would it be possible to at some point capture 60Hz or higher video of something with a lot of motion and contrast? Like Sonic or Bonk's Revenge emulated.
 

_wb_

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Good stuff, thanks for the continued updates.


ED, you have a really high frame rate camera, right? Would it be possible to at some point capture 60Hz or higher video of something with a lot of motion and contrast? Like Sonic or Bonk's Revenge emulated.
Yes, that would be pretty cool, a ghosting comparison between the Pandora and Pyra screens!

The resolution is insane, if you wouldn't know better you could think it's a 21" monitor on those pictures :)
 

Mr_Loon

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Thanks for the update, always good to see progress being made :)

From another recent post we learned that the Pyra screen is not the screen used with the Nexus 5, are there any existing devices that use the screen that will be used for Pyra?
 

EvilDragon

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Good stuff, thanks for the continued updates.


ED, you have a really high frame rate camera, right? Would it be possible to at some point capture 60Hz or higher video of something with a lot of motion and contrast? Like Sonic or Bonk's Revenge emulated.
That's what I want to do, yes.


But I first need emulators running on the devboard and get the adaptor PCB so I can connect my display as well ;)


It should be a lot better. The Pandora LCD has 30ms refresh time (or was it 35?) And the new one has 20ms. Haven't seen anything faster on a non-OLED small screen yet.
 

FaeMinx

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Looks like I'll be able to do some serious graphics work on the Pyra. :)

Any idea how many pressure levels will register with the resistive layer you intend to use?

Sent from my GT-N5100 using Tapatalk 4
 

cwall

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Great work Nikolaus the display looks great, feel your pain on the incomplete data sheet.  Guess Ed will be hanging around taking more pictures on the weekend.  Thanks for sharing your journey on what it took to get the display up, can not believe how clear and sharp it looks.
 
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