Pjhants
Posts: 2
Joined: Fri Jan 25, 2019 7:45 am

Re: STICKY: HOWTO: Create Custom HDMI modes

Fri Jan 25, 2019 7:51 am

I am helping a friend interface an HDMI LCD display to a Pi. The display is borderless and a specific size to replicate a flight simulator instrument panel. I have tried creating a custom resolution but without success. I can't get a stable display at all. I get a flashing backlight or if anything is displayed it is intermittent and repeated across the panel.

The display will work on a PC graphics card (GTX1080Ti) with the following settings:

- 720 x 1280.
- 60Hz.
- 8 bit.
- Colour Format RGB
- Colour spacing SDR.

The display itself is a: Sharp LS060R1SX01.
The driver chip is Toshiba 358870XBG.
So far we have failed to find any detailed data sheets for the Sharp display.

I think it's default resolution is 1440 X 2560 which is probably too much for the Pi but I can't even get a custom setting to run:

Amongst other settings suggested on this thread I have tried even standard 16x9 resolutions. I also tried:

hmdi_cvt 1440 720 60
hdmi_group=2
hdmi_mode=87

I can't find any timings info for the display Does anyone have any ideas or suggestions?

dom
Raspberry Pi Engineer & Forum Moderator
Raspberry Pi Engineer & Forum Moderator
Posts: 5230
Joined: Wed Aug 17, 2011 7:41 pm
Location: Cambridge

Re: STICKY: HOWTO: Create Custom HDMI modes

Tue Jan 29, 2019 12:23 pm

Pjhants wrote:
Fri Jan 25, 2019 7:51 am
hmdi_cvt 1440 720 60
hdmi_group=2
hdmi_mode=87

I can't find any timings info for the display Does anyone have any ideas or suggestions?
Unless the data sheet says it supports [email protected] then this is very unlikely to work.

The actual resolution 1440x2560x60 requires a pixel clock of 221MHz (actually more due to blanking),
so that won't work without overclock settings.
May be some info here: https://www.raspberrypi.org/forums/view ... 3#p1348063

chrhartz
Posts: 1
Joined: Tue Feb 26, 2019 10:54 pm

Re: STICKY: HOWTO: Create Custom HDMI modes

Tue Feb 26, 2019 11:41 pm

Hi all,

I made a pcb with the CM3L compute module and TFP401A HDMI to ttl decoder. I am using the DS90C385A
ttl to LVDS driver from TI to drive a 10.1" 1280x800 IPS display from Duobond displays.

It works generally. I am getting a stable picture with expected size, no flickering and colors are displayed normally.
So it seems the h- and v-sync is working and the color channels are connected the right way.

But the display is almost unreadable. It seems that there is still a problem with the pixel clock or something else.
I have tried different hdmi_timings without success. Also different cvt modes, driver settings and so on with no luck.

I made the pcb very carefully with impedance control, 4 layers, length matching and differential pair length matching better
than 0.2 mm. So I am hoping the pcb is not forcing the problem. :?

In fact this is my first HDMI and LVDS design and I have no experience so far. I grabbed all informations about it from
the datasheets, Adafruit designs, reference design from TI and other resources.

It would be very helpful if someone can give me a hint for the correct display timing. There are a lot of parameters that
can be changed and I don´t know where to start. :(

I bought a RTD2660 driver board together with the lcd. Unfortunally the RPi is not able to readout the EEDID EEPROM.
I was hoping the chinese guys programmed the EEDID correctly so I can fetch the correct timing values but no hope
from this side. The RTD2660 is displaying the picture perfectly... Should I switch to this chip? :roll:

Chris

Image

Image

Image

mosoto
Posts: 1
Joined: Tue Mar 12, 2019 12:30 am

Re: STICKY: HOWTO: Create Custom HDMI modes

Tue Mar 12, 2019 12:53 am

I have a Samsung Ultra Widescreen Monitor s34e790c (3440 x 1440 resolution) and I was recently struggling to get it to work with my raspberry pi 3b+ at that resolution. I finally got it to work so I figured I'd share my findings here in case it helps anyone else.

Ultimately, what helped me the most was running:

Code: Select all

/opt/vc/bin/tvservice -d edid.dat; /opt/vc/bin/edidparser edid.dat
This dumped the various modes for the monitor including a 50hz 3440x1440 and a 30hz 3440x1440 which were unrecognized. Running at 30hz worked right off the bat with a custom hdmi timing.

Code: Select all

hdmi_drive=2
hdmi_ignore_edid=0xa5000080
hdmi_group=2
hdmi_mode=87
hdmi_timings=3440 0 48 32 80 1440 1 3 10 8 0 0 0 30 0 157788000 7
max_framebuffer_width=3440
max_framebuffer_height=1440
framebuffer_width=3440
framebuffer_height=1440
Trying to run it at 50hz, however, was another matter. The edidparser dump showed that this should be the timings:

Code: Select all

hdmi_timings=3440 1 48 32 80 1440 0 3 10 21 0 0 0 50 0 265320000 7
hdmi_pixel_freq_limit=265320000
I adjusted the hdmi pixel freq limit since I read in one of these pages that the limit is somewhere around 160mhz. Unfortunately, did this not work. The monitor would continously fail.

Ultimately, I found that I needed to overclock the raspberry pi to get it to work. I suppose this is too high a resolution for the standard raspberry pi settings. This is what I ended up using for the overclocking. I can't claim to understand all of it and I wouldn't recommend doing this but I'll paste them in case anyone wants to play around with it.

Code: Select all

gpu_mem=256
force_turbo=1
hdmi_ignore_cec_init=1
arm_freq=1050
core_freq=500
sdram_freq=600
over_voltage=6
gpu_freq=500
This page was useful in understanding some of this:
https://elinux.org/RPiconfig

With the overclock and I did get the monitor to work at 50hz though ultimately I reverted to 30hz as I'm not sure what the overclocking will do to the longevity of my pi.

Anyway, hope that is useful.

aBUGSworstnightmare
Posts: 1242
Joined: Tue Jun 30, 2015 1:35 pm

Re: STICKY: HOWTO: Create Custom HDMI modes

Tue Mar 19, 2019 11:47 am

chrhartz wrote:
Tue Feb 26, 2019 11:41 pm
Hi all,

I made a pcb with the CM3L compute module and TFP401A HDMI to ttl decoder. I am using the DS90C385A
ttl to LVDS driver from TI to drive a 10.1" 1280x800 IPS display from Duobond displays.

It works generally. I am getting a stable picture with expected size, no flickering and colors are displayed normally.
So it seems the h- and v-sync is working and the color channels are connected the right way.

But the display is almost unreadable. It seems that there is still a problem with the pixel clock or something else.
I have tried different hdmi_timings without success. Also different cvt modes, driver settings and so on with no luck.

I made the pcb very carefully with impedance control, 4 layers, length matching and differential pair length matching better
than 0.2 mm. So I am hoping the pcb is not forcing the problem. :?

In fact this is my first HDMI and LVDS design and I have no experience so far. I grabbed all informations about it from
the datasheets, Adafruit designs, reference design from TI and other resources.

It would be very helpful if someone can give me a hint for the correct display timing. There are a lot of parameters that
can be changed and I don´t know where to start. :(

I bought a RTD2660 driver board together with the lcd. Unfortunally the RPi is not able to readout the EEDID EEPROM.
I was hoping the chinese guys programmed the EEDID correctly so I can fetch the correct timing values but no hope
from this side. The RTD2660 is displaying the picture perfectly... Should I switch to this chip? :roll:

Chris

Image

Image

Image
Your timing is incorrect! post your config.txt settings. Is your TFP401A configured/wired correctly?

User avatar
antiriad
Posts: 131
Joined: Sun Nov 17, 2013 7:38 pm
Location: Italy
Contact: Twitter

Re: STICKY: HOWTO: Create Custom HDMI modes

Sat Mar 23, 2019 1:54 pm

Hello,
it is technically possible to set a custom video resolution of 320x200 with a VGA666?

Thank you!

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