IRDeveloper
Posts: 5
Joined: Thu Jul 12, 2018 3:19 pm

Horizontal White Line on DPI Display of Raspberry

Thu Jul 12, 2018 3:32 pm

Hi Guys
i want to use DPI Of raspberry pi 3 B to using raw LCD Panel.
i have made a simple board (HEADER Board) to converting GPIO_HEADER of raspberry to a FPC-40PIN.
and i have used a simple board to converting 40pin lcd to 50 pin.

Now, Raspberry could driver the LCD, and i have picture on LCD now, and all color is OK.
but i have a problem:

i have lots of horizontal white (faded) line on my screen.

i have uploaded picture of my display : https://pasteboard.co/Hu8chBB.png

what could be my problem?

aBUGSworstnightmare
Posts: 1097
Joined: Tue Jun 30, 2015 1:35 pm

Re: Horizontal White Line on DPI Display of Raspberry

Thu Jul 12, 2018 7:26 pm

... Although you have an image (which is good) are you sure your timing and settings are correct?

IRDeveloper
Posts: 5
Joined: Thu Jul 12, 2018 3:19 pm

Re: Horizontal White Line on DPI Display of Raspberry

Fri Jul 13, 2018 5:53 am

almostly i tested any possible setting!
i think it should be about hardware circuit, because even when i disable Raspberry's DPI module, i will have black screen, but again this horizontal lines exist!


its the circuit im using:

https://pasteboard.co/HudPXTp.png

and i have connected output of this circuit to another module(40pin to 50pin converter)

aBUGSworstnightmare
Posts: 1097
Joined: Tue Jun 30, 2015 1:35 pm

Re: Horizontal White Line on DPI Display of Raspberry

Fri Jul 13, 2018 9:29 am

IRDeveloper wrote: almostly i tested any possible setting!
i think it should be about hardware circuit, because even when i disable Raspberry's DPI module, i will have black screen, but again this horizontal lines exist!


its the circuit im using:

https://pasteboard.co/HudPXTp.png

and i have connected output of this circuit to another module(40pin to 50pin converter)
DPI disable or everyting disconnected? What is your cable lenght for DPI Interface (between Raspberry and TFT)? Have you checked for interference issues?

Anyhow, I still think your Timing is incorrect (when looking at all the picture from your first post). Which Display do you want to connect and how are your config.txt Settings?

IRDeveloper
Posts: 5
Joined: Thu Jul 12, 2018 3:19 pm

Re: Horizontal White Line on DPI Display of Raspberry

Fri Jul 13, 2018 10:24 am

i have tested with DPI disabled, not disconnected

Its the display:
http://www.actablet.com/universal-73001 ... 10628.html


and my config:

Code: Select all

dtoverlay=dpi24
enable_dpi_lcd=1
display_default_lcd=1
dpi_group=2
dpi_mode=87
dtparam=spi=off
dtparam=i2c_arm=off
dpi_output_format=0x43017
hdmi_cvt=1024 600 60 6 0 0 0

aBUGSworstnightmare
Posts: 1097
Joined: Tue Jun 30, 2015 1:35 pm

Re: Horizontal White Line on DPI Display of Raspberry

Fri Jul 13, 2018 11:35 am

As you've build some Adapter board let's me assume you have the full data sheet of the display on hands.

You should get rid of

Code: Select all

hdmi_cvt=1024 600 60 6 0 0 0
and use correct timing (all details available from the Display data sheet) instead

Code: Select all

hdmi_timings=<h_active_pixels> <h_sync_polarity> <h_front_porch> <h_sync_pulse> <h_back_porch> <v_active_lines> <v_sync_polarity> <v_front_porch> <v_sync_pulse> <v_back_porch> <v_sync_offset_a> <v_sync_offset_b> <pixel_rep> <frame_rate> <interlaced> <pixel_freq> <aspect_ratio>
I've never had any luck with the simply 'hdmi_cvt' definition.

IRDeveloper
Posts: 5
Joined: Thu Jul 12, 2018 3:19 pm

Re: Horizontal White Line on DPI Display of Raspberry

Fri Jul 13, 2018 1:19 pm

my second adapter connected pin_8 of 50pin-fpc (MODE) to 3.3v....
because its MODE pin, i assumed i have no choice except DE mode.(is this correct?)
and i assumed in DE mode, i should use hdmi_cvt(is this correct?)

aBUGSworstnightmare
Posts: 1097
Joined: Tue Jun 30, 2015 1:35 pm

Re: Horizontal White Line on DPI Display of Raspberry

Fri Jul 13, 2018 6:16 pm

No spec = same as using crystall ball
As my crystall ball is under repair atm no answer possible for me
Good luck!
Anyhow: use hdmi_timing as this allows you to adjust correct timing.

IRDeveloper
Posts: 5
Joined: Thu Jul 12, 2018 3:19 pm

Re: Horizontal White Line on DPI Display of Raspberry

Mon Jul 16, 2018 7:25 pm

Problem Solved!

the issue was with Gate voltage (+10.4v & 16v) for driving LCD (there was lot of noise).

Return to “Interfacing (DSI, CSI, I2C, etc.)”