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#1 2021-11-11 01:59:40

Bob132
Member
Registered: 2021-11-10
Posts: 8

Help with Duobond 6.6" 4098x2560 Monochrome LCD DBT066MONO

I purchased a 6.6 inch 4k (4098x2560) true monochrome (square pixels, no subpixels) from Duobond on Alibaba.

I am trying to get it working with NanoDLP, but I am having some issues. It looks like every other vertical pixel column turns white if anything is displayed (if all black is showed then the whole screen goes blank). Also all of the horizontal dimensions are doubled. I installed the NanoDLP SD Card image file on a Raspberry Pi 4 4GB.

Here are my NanoDLP display settings. 2160x2560 is the highest resolution I have been able to use and still get a mostly centered and not torn up image.
UaXyJuF.png

Here are what the calibration images look like:
Boundary & Size: (real square dimensions were measured at 100mm x 75mm)
PjAJqH9.jpg

Focus Calibration:
jLjh8zT.jpg

Pixel Check: (horizontal)
YQV47Uo.jpg

Pixel Check: (vertical)
CEZO8cC.jpg

Here is my config file:

dtparam=i2c_arm=on
dtparam=spi=on

disable_splash=1
boot_delay=0
dtoverlay=pi3-disable-bt

[pi4]
dtoverlay=vc4-fkms-v3d
max_framebuffers=2

[all]
disable_camera_led=1
hdmi_pixel_encoding=2
start_x=0
gpu_mem=128
enable_uart=1

dtparam=i2c_arm=on

enable_uart=1

[HDMI:0]
hdmi_ignore_edid=0xa5000080
display_hdmi_rotate=0x10000
hdmi_drive=1
hdmi_timings=1440 0 100 20 100 2560 0 20 2 24 0 0 0 40 0 173040000 3
hdmi_group=2
hdmi_mode=87
hdmi_pixel_freq_limit=400000000
hvs_priority=0x32ff
max_framebuffer_width=2160
max_framebuffer_height=3840
framebuffer_width=1440
framebuffer_height=2560
framebuffer_ignore_alpha=1

hdmi_pixel_encoding=2
disable_overscan=1

Duobond also provided me with two config files. One the Raspberry Pi 4:

#  config rpi4_6.6_mono_4K_Duobond

disable_camera_led=1
dtparam=i2c_arm=on
#dtparam=audio=off

#dtoverlay = pi3-disable-bt
enable_uart=1

[HDMI:0]
hdmi_ignore_edid=0xa5000080
display_hdmi_rotate=0x10000
hdmi_drive=1
# hdmi_timings=2160 0 105 20 100 3840 0 30 2 29 0 0 0 24 0 223290000 3
hdmi_timings=1440 0 100 20 100 2560 0 20 2 24 0 0 0 40 0 173040000 3
hdmi_group=2
hdmi_mode=87
hdmi_pixel_freq_limit=400000000
hvs_priority=0x32ff
max_framebuffer_width=2160
max_framebuffer_height=3840
framebuffer_width=1440
framebuffer_height=2560
framebuffer_ignore_alpha=1

hdmi_pixel_encoding=2
disable_overscan=1

And one for the Raspberry Pi 3:

force_trubo=1
gpu_freq=300
core_freq=400


# HDMI {ݒ Basic configuration
hdmi_pixel_freq_limit=400000000
hdmi_timings=1440 0 100 20 100 2560 0 20 2 24 0 0 0 40 0 173040000 0
hdmi_drive=2
disable_overscan=1
max_framebuffer_width=2560
max_framebuffer_height=2560

# Portrait or Landscape Setting
#Portrait-1 (tL, Flexible cable is bottom side.)
display_rotate=0
framebuffer_width=1440
framebuffer_height=2560

# Landscape-1 (tLE, Flexible cable is right side.)
#display_rotate=1
#framebuffer_width=1920
#framebuffer_height=1200

# Portrait-2 (tL, Flexible cable is upper side.)
#display_rotate=2
#framebuffer_width=1200
#framebuffer_height=1920

# Landscape-2 (tL, Flexible cable is left side.)
#display_rotate=3
#framebuffer_width=1920
#framebuffer_height=1200

# ȉ̓IWiconfig.txt (RASPBIAN JESSIE, November 2015) ̓e
# Original contents of config.txt (RASPBIAN JESSIE, November 2015) is as follows.

# For more options and information see
# http://www.raspberrypi.org/documentation/configuration/config-txt.md
# Some settings may impact device functionality. See link above for details

# uncomment if you get no picture on HDMI for a default "safe" mode
# hdmi_safe=1

# uncomment this if your display has a black border of unused pixels visible
# and your display can output without overscan
#disable_overscan=1

# uncomment the following to adjust overscan. Use positive numbers if console
# goes off screen, and negative if there is too much border
#overscan_left=16
#overscan_right=16
#overscan_top=16
#overscan_bottom=16

# uncomment to force a console size. By default it will be display's size minus
# overscan.
#framebuffer_width=1280
#framebuffer_height=720

# uncomment if hdmi display is not detected and composite is being output
#hdmi_force_hotplug=1

# uncomment to force a specific HDMI mode (this will force VGA)
#hdmi_group=1
#hdmi_mode=1

# uncomment to force a HDMI mode rather than DVI. This can make audio work in
# DMT (computer monitor) modes
#hdmi_drive=2

# uncomment to increase signal to HDMI, if you have interference, blanking, or
# no display
#config_hdmi_boost=4

# uncomment for composite PAL
#sdtv_mode=2

#uncomment to overclock the arm. 700 MHz is the default.
#arm_freq=800

# Uncomment some or all of these to enable the optional hardware interfaces
#dtparam=i2c_arm=on
#dtparam=i2s=on
#dtparam=spi=on

# Uncomment this to enable the lirc-rpi module
#dtoverlay=lirc-rpi

# Additional overlays and parameters are documented /boot/overlays/README

# Enable audio (loads snd_bcm2835)
dtparam=audio=off

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#2 2021-11-12 06:57:59

Shahin
Administrator
Registered: 2016-02-17
Posts: 3,517

Re: Help with Duobond 6.6" 4098x2560 Monochrome LCD DBT066MONO

Are the dimensions correct?

Do below actions see, how each one affect the picture:
1. Remove framebuffer path
2. Change to standard display

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#3 2021-11-12 23:31:11

Bob132
Member
Registered: 2021-11-10
Posts: 8

Re: Help with Duobond 6.6" 4098x2560 Monochrome LCD DBT066MONO

The width dimension is not correct, but the height seems to be correct. It shows 50x75 on screen, but the actual measured dimensions of the box are 100mm.

I removed the framebuffer path (/dev/fb0) and rebooted and then nothing happened when attempting to display any calibration image, just a black screen.

After adding the framebuffer back, I changed to standard display and this was the result:
7n8KT22.jpg

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#4 2021-11-13 07:34:17

Shahin
Administrator
Registered: 2016-02-17
Posts: 3,517

Re: Help with Duobond 6.6" 4098x2560 Monochrome LCD DBT066MONO

Change to non-standard.
Also increase gpu_mem.
Instead of 2160 put 4098 on display resolution, share what being displayed. Test with both framebuffer and without it.

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#5 2021-11-13 08:37:25

Bob132
Member
Registered: 2021-11-10
Posts: 8

Re: Help with Duobond 6.6" 4098x2560 Monochrome LCD DBT066MONO

I changed back to non-standard, and changed the GPU memory from 128 to 256. The result was identical to my original post.

Below is the "Boundary & Size" result when the resolution is set to 4098x2560. Removing the framebuffer path had the same result as the last time, just a black screen for all tests.

Something I should note is that the when I have seen a terminal come up (which happens for a split second after I click "Projector / UV Turn On"), the text is white on a black background without the white lines every-other pixel. Although the white text is stretched to three times the width it should be due to the screen having square mono pixels.

DhXzk2L.jpg

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#6 2021-12-22 18:44:32

Bob132
Member
Registered: 2021-11-10
Posts: 8

Re: Help with Duobond 6.6" 4098x2560 Monochrome LCD DBT066MONO

I am not sure how to fix the issue. What should I try next?

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#7 2021-12-25 06:59:14

Shahin
Administrator
Registered: 2016-02-17
Posts: 3,517

Re: Help with Duobond 6.6" 4098x2560 Monochrome LCD DBT066MONO

Please, share latest configuration status. I still think it is a slight error on setup parameters

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#8 2021-12-25 07:16:33

Bob132
Member
Registered: 2021-11-10
Posts: 8

Re: Help with Duobond 6.6" 4098x2560 Monochrome LCD DBT066MONO

The configuration I shared originally is the config I am currently using. Is there any information you need that I have not shared yet?

Last edited by Bob132 (2021-12-25 07:17:06)

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#9 2021-12-28 20:28:29

Mina
Member
Registered: 2021-12-28
Posts: 3

Re: Help with Duobond 6.6" 4098x2560 Monochrome LCD DBT066MONO

Try changing the horizontal resolution in Nanodlp to 4320, and use non-standard monochrome display.

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#10 2021-12-30 07:13:38

Bob132
Member
Registered: 2021-11-10
Posts: 8

Re: Help with Duobond 6.6" 4098x2560 Monochrome LCD DBT066MONO

I tried that and I thought it would work, but it did not. I realized the screen registers at 1440x2560, but only displays a 1366x2560 color image (which ends up actually being 4098x2560 because it has square pixels instead of subpixels). The column pixels on the right side of the screen are cutoff and not displayed.

This is what the image looks like when the NanoDLP display settings are set to 4320x2560 with the non-standard option. The Raspberry pi is driving it 1440x2560.
yUZ0bNu.jpg

Here is a test image that I created in paint.net and converted to a subpixel image using this tool then added a column of 74 pixels to the right side and displayed using Linux Framebuffer Imageviewer (FBI). The grey background is actually a black and white checkerboard pattern which is displaying successfully. I now know that my raspberry pi config is correct and the issue should only be with the NanoDLP configuration.
cz3snSZ.png
U1zG5Y2.png
B27c9Dh.png

Last edited by Bob132 (2021-12-31 01:01:27)

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#11 2021-12-30 11:00:31

Mina
Member
Registered: 2021-12-28
Posts: 3

Re: Help with Duobond 6.6" 4098x2560 Monochrome LCD DBT066MONO

I have it displaying the correct dimensions, using Duobond Config file, and setting horizontal resolution in Nanodlp at 4320.
However, I'm having different types of problems with the display, mostly with black areas being not completely dark.
I am trying to post some photos but for some reason I can't.

Last edited by Mina (2021-12-30 11:03:12)

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#12 2021-12-31 01:07:00

Bob132
Member
Registered: 2021-11-10
Posts: 8

Re: Help with Duobond 6.6" 4098x2560 Monochrome LCD DBT066MONO

@Mina would you mind sharing your exact config.txt and NanoDLP display settings?

To post an image I would recommend uploading to a site like Imgur and then putting the image URL between the img tags like this

[img]https://www.nanodlp.com/forum/img/test.png[/img]

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#13 2022-01-01 08:52:08

Mina
Member
Registered: 2021-12-28
Posts: 3

Re: Help with Duobond 6.6" 4098x2560 Monochrome LCD DBT066MONO

Hi bob, here is the nanodlp display settings:

Screenshot-2022-01-01-104202.jpg


The config file is the same one Duobond sent you:

#  config rpi4_6.6_mono_4K_Duobond

disable_camera_led=1
dtparam=i2c_arm=on
#dtparam=audio=off

#dtoverlay = pi3-disable-bt
enable_uart=1

[HDMI:0]
hdmi_ignore_edid=0xa5000080
display_hdmi_rotate=0x10000
hdmi_drive=1
# hdmi_timings=2160 0 105 20 100 3840 0 30 2 29 0 0 0 24 0 223290000 3
hdmi_timings=1440 0 100 20 100 2560 0 20 2 24 0 0 0 40 0 173040000 3
hdmi_group=2
hdmi_mode=87
hdmi_pixel_freq_limit=400000000
hvs_priority=0x32ff
max_framebuffer_width=2160
max_framebuffer_height=3840
framebuffer_width=1440
framebuffer_height=2560
framebuffer_ignore_alpha=1

hdmi_pixel_encoding=2
disable_overscan=1

And here are the displays:

Whats-App-Image-2021-12-30-at-12-31-46.jpg

Whats-App-Image-2021-12-30-at-12-31-46-1.jpg

Whats-App-Image-2021-12-30-at-12-31-46-2.jpg

If you notice in the last shot, I am exposing a rectangle, but you will notice that the vertical extensions of the rectangle is adequately black, however, to the right and left of the rectangle, the screen is allowing too much UV to pass through, which makes printing impossible.

Last edited by Mina (2022-01-01 09:07:55)

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