3.5" 640x480 DPI screen

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MaxPof
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3.5" 640x480 DPI screen

Post by MaxPof » Wed Sep 29, 2021 4:51 am

EDIT
TL;DR: We are talking about this screen:
https://www.waveshare.com/3.5inch-dpi-lcd.htm
which apparently has never been tested. So I do it 6 posts later :)
_______________________________________________________
Hi everyone!

After a long time, I just resumed my build, abandoned because the composite screen is too bad to play the games that interest me.
Here is where I stopped: https://www.sudomod.com/forum/viewtopic.php?f=43&t=9948

So I want to change the screen but it's hard to find updated information and I'm not sure which screen is still the best option.

From what I read, DPI seems the best screen if you have enough GPIO, which is my case.

So people seems to generally use the LQ035NC111 screen with thinkerboy adapter
https://www.tinkerboy.xyz/product/tinke ... i-adapter/

But I try to find a better screen resolution.

This topic was promising but doesn't seem to be updated anymore.

And I found this 3.5" 640x480 DPI screen
https://thepihut.com/products/3-5-ips-d ... spberry-pi

It seems perfect. A little bit expensive but not so much considering you don't have to buy thinkerboy adapter.
But I've found nothing on this forum about this screen...
Is there a problem I can't see? Or the screen is just very new?
Or is there a better alternative?

Thanks!
Last edited by MaxPof on Tue Nov 09, 2021 10:46 am, edited 2 times in total.

floppes
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Re: 3.5" 640x480 DPI screen

Post by floppes » Sun Oct 03, 2021 3:39 am

This really looks like a perfect match!

About 2.5 years ago I was searching for a fitting 3.5" display with a resolution of more than 320x280 to fit inside the Game Boy shell. I found quite a few, but all were a few millimeters too wide for the shell. The display you found fits easily! And it has an IPS panel (better image quality when viewed from the side) and a DPI interface (the best interface in my opinion: no hassle with an internal HDMI cable and higher refresh rates than SPI).

The only downsides may be the thickness, the price and the touchscreen (which in my opinion is useless for a Game Boy).

I'd give it a try!

MaxPof
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Re: 3.5" 640x480 DPI screen

Post by MaxPof » Sun Oct 03, 2021 6:27 am

Hi !

Thanks, yeah I think I'll order one...

I just saw your build, nice one ! And your board seems very convenient !

For the touch screen, I wonder if it's possible to remove the touch layer from the screen. I don't know if it's integrated, or just a glass layer.

And I don't know if the component on the board of the screen are only for the touch part, (so I could remove it), or if there is some mandatory power management (or other) in there...

floppes
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Re: 3.5" 640x480 DPI screen

Post by floppes » Sun Oct 03, 2021 1:14 pm

On the board you can see an AMS1117 voltage regulator, an STM8S003F3 microcontroller (probably for initializing the display) and a Goodix touch screen controller on the orange/brown flat flex cable. The small coil probably belongs to another power supply. Therefore you will need most of the components on the board ;)

From my experience, touch screens are usually glued onto the panel and can be removed very carefully.

Sudafed
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Re: 3.5" 640x480 DPI screen

Post by Sudafed » Mon Oct 04, 2021 7:29 am

Im going to use the cheap "mhs 3.5" display from aliexpress for my next build. Its 480x320 and has a fast spi interface and a spi to dpi converter. I got about 30 fps out of it. Fitting it will require some trimming of the bezel as with the 3.5 hdmi screens some people here are using.

MaxPof
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Re: 3.5" 640x480 DPI screen

Post by MaxPof » Tue Oct 05, 2021 4:21 pm

Ok, so I've just order it!
Directly from Waveshare website but it seems to come from china, it may take some time to deliver... (I was too unsure of taxes with PiHut from GB).

I'll make a return when I got it

@Sudafed: yeah, I saw those too. But if I can avoid to trim anything now everything is in place...

The frame of the display I found is apparently exactly the same dimensions than these 3,5" rear camera composite screens. If it's true, I would just have to change the screens, without touching anything

MaxPof
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Re: 3.5" 640x480 DPI screen

Post by MaxPof » Tue Nov 09, 2021 10:40 am

Hi!

So, I received my screen (very quickly in fact, I didn't take the time to write a feedback earlier, sorry)
Some photos:

Image
Image

So it's pretty thick because of the touch panel and the glass screen. BUT, it's exactly the same frame than those composite screens.
So I remove all the frame (it's just clipped with the white plastic part of the screen)

Image

(You can see the inside of the touch panel on the right.)

So now I can swap them and have a DPI screen without touch panel to save some room on this build.
And save the touch screen with the old composite screen for another project (not sure it will works but i'm quite confident that I just have to connect the touch screen connector to GPIO (I2c)

Image
DPI screen without touch panel on the left, composite screen with touch screen on the right.

Image
Almost thin!

So yeah, unless your RPi is perfectly aligned with the connector in your build (which is possible I think), you'll need some ribon to connect everything.

I tried those two:
https://fr.aliexpress.com/item/33030523 ... 6c37JnRXMF
https://fr.aliexpress.com/item/33020373 ... 6c37JnRXMF

Wasn't sure about the sufficient strength of the small one but it appears that this is ok (and the big on is a little too big)

Image

Everything fits!
I have to put the connector upside down and do some modification as you can see, because I plugged it in the bottom side of my RPi. I didn't have the choice but it should be easier if you solder it the right side...

Image


Make it works (RPi 4):

So the screen is plug and play, but not with Retropie....

Waveshare give a good wiki to help with the screen:
https://www.waveshare.com/wiki/3.5inch_DPI_LCD
I try to follow that but I have nothing on screen.
I just have to comment

Code: Select all

dtoverlay=waveshare-35dpi-3b-4b
dtoverlay=waveshare-35dpi-3b
Seems pretty logical because I don't use a RPi3, but nothing is explain...

So if I remember well, it works like that but:
In config.txt file, you have this line (again RPi 4 only, didn't test with other):

Code: Select all

dtoverlay=vc4-fkms-v3d
Which enable 3D acceleration but made many command from config.txt obsolete. (like "display_rotate")
So the wiki told you to comment this line
Note: For Raspberry Pi 4, you need to comment out dtoverlay=vc4-fkms-V3D.
Which is supposed to make the screen work (and it does). But retropie can't run without vc4-fkms-v3d...
So you have to leave it and that why you have to make some change in the config.txt file.

To make "display_rotate=1" work, you have to modify cmdline.txt, see here:
https://forums.raspberrypi.com/viewtopic.php?t=247619

Now, for me the screen was almost ok, just some bad "flickering"/bad display.
This came from this line:

Code: Select all

hdmi_timings=640 0 20 10 10 480 0 10 5 5 0 0 0 60 0 60000000 1
I don't understand all the parameters in this line (and didn't try for now).
First I suspect that it should be dpi_timings instead of hdmi_timings...
And I finally just comment it to get rid of any display flickering, so yeah, I suppose there is a mistake here



And the resolution?

It's.... perfect!!

I can finally play n64 games with the original image!
I undo all the modifications I had to do to make the composite screen legible (enlarge retropie font, bigger terminal,...)
All is now in default size (the terminal too) and it's very clear


Sorry, it's hard to pay homage to a screen in photos.
Image

Image
This is the original font size!

Hope it will help!


EDIT:

This is my config.txt:

Code: Select all

[all]
dtoverlay=vc4-fkms-v3d


disable_splash=1


gpio=0-9=a2
gpio=12-17=a2
gpio=20-25=a2
dtoverlay=dpi18
enable_dpi_lcd=1
display_default_lcd=1
extra_transpose_buffer=2
dpi_group=2
dpi_mode=87
dpi_output_format=0x6f006
#dpi_timings=640 0 20 10 10 480 0 10 5 5 0 0 0 60 0 60000000 1
#dtoverlay=waveshare-35dpi-3b-4b
#dtoverlay=waveshare-35dpi-3b
#dtoverlay=waveshare-35dpi-4b
#display_rotate=2
disable_touchscreen=1
So I visibly comment

Code: Select all

dtoverlay=waveshare-35dpi-4b
too... don't remember why.
If someone is comfortable with this file, don't hesitate to give your feedback

sgtgrumbles
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Re: 3.5" 640x480 DPI screen

Post by sgtgrumbles » Wed Nov 24, 2021 12:25 am

Excellent find, thanks for sharing!

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