Porte
Posts: 7
Joined: Wed Jun 12, 2019 11:00 am

CM3 DPI connection

Wed Jun 12, 2019 11:15 am

I tried to connect 50 pin 1024x600, 10.1' TFT LCD to CM3 DPI port. It is running but I can not get good image on LCD. I applied these settings:

If 1024x600 Resolution LCD(such us 7 inch,10.1 inch) and VGA:

dtoverlay=dpi24
enable_dpi_lcd=1
display_default_lcd=1
dpi_group=2
dpi_mode=87
dpi_output_format=0x6f005
hdmi_cvt 1024 600 60 6 0 0 0

I can see raspbian desktop on LCD but there is a problem. I can send you a picture of LCD if you send me an email. How can I get a good image on 1024x600, 10.1' 50 pin TFT from CM3 DPI conneciton? thank you.

6by9
Raspberry Pi Engineer & Forum Moderator
Raspberry Pi Engineer & Forum Moderator
Posts: 6884
Joined: Wed Dec 04, 2013 11:27 am
Location: ZZ9 Plural Z Alpha, aka just outside Cambridge.

Re: CM3 DPI connection

Wed Jun 12, 2019 12:33 pm

Put the image on any file sharing site (eg Dropbox, Google Drive, imgur, etc), and share the link.
Software Engineer at Raspberry Pi Trading. Views expressed are still personal views.
I'm not interested in doing contracts for bespoke functionality - please don't ask.


6by9
Raspberry Pi Engineer & Forum Moderator
Raspberry Pi Engineer & Forum Moderator
Posts: 6884
Joined: Wed Dec 04, 2013 11:27 am
Location: ZZ9 Plural Z Alpha, aka just outside Cambridge.

Re: CM3 DPI connection

Wed Jun 12, 2019 2:13 pm

Your choice of file sharing site isn't nice seeing as Google gives all sorts of warnings about it. I've resized and added the image directly as the details isn't required.

To my eyes that is simply that you've got the wiring wrong. There is no standard wiring for DPI displays, therefore you have to check it for yourself. By the looks of it red is being passed to green (looking at the raspberry), and I'd suspect that the bit order isn't being respected either.

Are you sure that it is wired up as 24bit? The output format bits in dpi_output_format are set to 5 for RGB666 (18bit), not 24bit. See https://www.raspberrypi.org/documentati ... /README.md for details, but I'd expect something ending in 7 for 24bpp (eg 0x6f007)
Attachments
system.jpg
system.jpg (96.36 KiB) Viewed 525 times
Software Engineer at Raspberry Pi Trading. Views expressed are still personal views.
I'm not interested in doing contracts for bespoke functionality - please don't ask.

Porte
Posts: 7
Joined: Wed Jun 12, 2019 11:00 am

Re: CM3 DPI connection

Thu Jun 13, 2019 5:20 am

I saw all documents about DPI connections for CM3 on web.

http://www.rapidshare.com.cn/OARFPpv

You can se my connection schematics and pdf of LCD. I am usng 888 connection. According to this document I can change rgb order. I will try to change this order but I wonder if there is more adjustment that I have to set about DPI connection or change driver file for my LCD.

Aslo, there is not any connection and settings examples for 1024x600, 10.1" TFT LCD. Mybe there is something different for this LCD.

Thank you.

6by9
Raspberry Pi Engineer & Forum Moderator
Raspberry Pi Engineer & Forum Moderator
Posts: 6884
Joined: Wed Dec 04, 2013 11:27 am
Location: ZZ9 Plural Z Alpha, aka just outside Cambridge.

Re: CM3 DPI connection

Thu Jun 13, 2019 9:47 am

I'll draw your attention again to the config line

Code: Select all

dpi_output_format=0x6f005 
As per the documentation, bits 0-3 control the mode. You have them set to "5", therefore you are selecting mode 5 which is RGB666 (18bit mode), NOT mode 7 for RGB888 (24bit mode).
With mode 5 you'll be displaying the least significant bits of green as the most significant bits of blue, and will never drive red beyond 2bits out of the 8.

Code: Select all

dpi_output_format=0x6f007
would be the first change I would suggest.

There are no standards for DPI panels, therefore you'll find examples for specific models, but those can not be treated as general solutions for panels of that resolution.
Software Engineer at Raspberry Pi Trading. Views expressed are still personal views.
I'm not interested in doing contracts for bespoke functionality - please don't ask.

Porte
Posts: 7
Joined: Wed Jun 12, 2019 11:00 am

Re: CM3 DPI connection

Thu Jun 13, 2019 10:16 am

Thank you for your suggestion. I will try on saturday and let you know.

Porte
Posts: 7
Joined: Wed Jun 12, 2019 11:00 am

Re: CM3 DPI connection

Wed Jul 17, 2019 7:01 am

Hi,

Problem solved. Thank you.

Umit

aBUGSworstnightmare
Posts: 1357
Joined: Tue Jun 30, 2015 1:35 pm

Re: CM3 DPI connection

Thu Jul 18, 2019 1:46 pm

Porte wrote: Hi,

Problem solved. Thank you.

Umit
and how???

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