g3wd
Posts: 2
Joined: Mon Jan 18, 2016 11:53 pm

Driving LCD display using DPI

Tue Jan 19, 2016 12:33 am

I stumbled upon this article explaining how to drive a lcd using dpi via the gpio pins.
http://blog.reasonablycorrect.com/raw-dpi-raspberry-pi/

I had an old picture frame laying around so i thought i could modify it into a retro-pi emulation station.

The screen inside was a CLAA070LC05CW, not a very common model but i managed to get hold of a pretty well written data sheet.
CLAA070LC05CW is 7 color TFT-LCD(Thin Film Transistor Liquid Crystal Display)module composed of LCD panel,driver ICs and backlight.
The 7.0"screen produces a high resolution image that is composed of 800×480 pixel elements in a stripe arrangement.Display 262K colors by 6 Bit R.G.B signal input.
When i saw the pinout i got a bit confused, or rather the guide i was hoping to follow didn't provide any help.

My display has a lot more pins than the one in the guide, i have two clocks for instance, one horisontal and one vertical. Is it even going to be possible to drive this display from the raspi?
Im way in over my head(fun!), so if anyone can point me in the right direction i would be very greatfull.

connections used in the guide:
Image

pinout for my display:
Image

i have the entire datasheet if that would be of any help..

Thanks

6by9
Raspberry Pi Engineer & Forum Moderator
Raspberry Pi Engineer & Forum Moderator
Posts: 9904
Joined: Wed Dec 04, 2013 11:27 am
Location: ZZ9 Plural Z Alpha, aka just outside Cambridge.

Re: Driving LCD display using DPI

Tue Jan 19, 2016 10:50 am

Worth having a quick read through of the Adafruit Kippah blurb and tutorial for more background info.

Your display looks highly configurable with control lines for polarity selection (POL/43) and inverting control signals (REV/42) (though those sound like the same thing to me unless one is for control and one for data lines), output_enable, etc. That's more than many displays have.
Anyway, post the entire datasheet to dropbox or similar and we can have a squint. It may be that you can set it into a suitable mode that only needs one clock+hsync+vsync.
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.

g3wd
Posts: 2
Joined: Mon Jan 18, 2016 11:53 pm

Re: Driving LCD display using DPI

Tue Jan 19, 2016 4:44 pm

Thanks for the resources will go though them later today.
meanwhile here's the datasheet https://drive.google.com/file/d/0B8nwgT ... sp=sharing

I was thinking of doing this with a pi zero, even tough it doesn't have dedicated DSI port the gpio is all the same right?

6by9
Raspberry Pi Engineer & Forum Moderator
Raspberry Pi Engineer & Forum Moderator
Posts: 9904
Joined: Wed Dec 04, 2013 11:27 am
Location: ZZ9 Plural Z Alpha, aka just outside Cambridge.

Re: Driving LCD display using DPI

Tue Jan 19, 2016 5:48 pm

g3wd wrote:Thanks for the resources will go though them later today.
meanwhile here's the datasheet https://drive.google.com/file/d/0B8nwgT ... sp=sharing
I'll have a look later.
g3wd wrote:I was thinking of doing this with a pi zero, even tough it doesn't have dedicated DSI port the gpio is all the same right?
Yup, GPIO is the same so should be fine for DPI interface. You don't need the DSI interface for that.
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.

CPhoenix10
Posts: 1
Joined: Mon Sep 26, 2016 10:10 pm

Re: Driving LCD display using DPI

Mon Sep 26, 2016 10:16 pm

I've just found out that I have the same LCD available and would love to get this working with a Pi Zero too.
Has there been any progress with this? Likewise I'm in wayyy over my head but its one hell of a learning curve :)

(Sorry for any thread necromancy)

aBUGSworstnightmare
Posts: 2301
Joined: Tue Jun 30, 2015 1:35 pm

Re: Driving LCD display using DPI

Tue Sep 27, 2016 8:23 am

You will have to supply a lot of different voltages to the module to make it work correctly --> maybe not the best one to use when your learning...

ollo
Posts: 4
Joined: Wed Mar 06, 2013 12:51 pm

Re: Driving LCD display using DPI

Wed Nov 30, 2016 8:43 pm

Hi,

I spent several days (and nights) figuring out how to (successfully) configure my Pi0 for a 640x480 screen of type THG057VGLAC-H000 (You can get them for 20€ in Germany).
After reading many brilliant posts on this forum I found my Pi0 only generating output if the pixel frequency is set to 32000000 - and I did check CLK/Hsync/Vsync using my CRO. That left me wondering if there are any restrictions within the hdmi_timings group.

These settings worked for me:
# Pollin DPI-Display ArtNo. 121402 5.7' 640x480
dtoverlay=dpi18
framebuffer_width=640
framebuffer_height=480
enable_dpi_lcd=1
display_default_lcd=1
dpi_output_format=0x70015
hdmi_timings=640 0 103 88 56 480 0 34 3 31 0 0 0 60 0 32000000 1
dpi_group=2
dpi_mode=87

Although I achieved a flickerfree, pixel-perfect picture, I'm slightly worried to use a pixel clock of 32MHz instead of the recommended 25.2MHz as per datasheet.

Did I miss some detail?

/Oliver

aBUGSworstnightmare
Posts: 2301
Joined: Tue Jun 30, 2015 1:35 pm

Re: Driving LCD display using DPI

Fri Dec 02, 2016 6:21 am

Max. dot clock from the spec is 28.33MHz. Your operating it out of spec, but who cares? You will damage nothing. As long as it's working - fine.

I can see the same on my 9.2in display; it is not working at all with for clock set to 15.9MHz for me but is is working with these settings for another forum member.

PierreG
Posts: 8
Joined: Fri Dec 01, 2017 11:34 am

Re: Driving LCD display using DPI

Fri Jan 19, 2018 3:26 pm

Hi guys!

Does anybody know the maximum output performances DPI can offer?
I would like to output on a display 1024x768@60fps...
Thank you

happy Rpi works!

aBUGSworstnightmare
Posts: 2301
Joined: Tue Jun 30, 2015 1:35 pm

Re: Driving LCD display using DPI

Fri Jan 19, 2018 7:21 pm

XGA is no problem ; used it with a 15in already

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