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Troubleshooting • HDMI Output Resolution/Orientation Issues

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Hi - sorry for what will be quite a long post, but hopefully it will have everything needed in it! Any help that anyone can give will be very appreciated!

I have a Raspberry Pi 3B+ (with 1GB memory) that has been working as a VPN server for a while now and I am trying to turn it into a dashboard that will show a single webpage in kiosk mode (whilst still running the VPN in the background) in a portrait orientation. I am going to start with a clean install of the latest version of Raspberry Pi OS for carrying this out (given the old version hadn't been updated in many years!).

I have ordered this screen off Ali Express https://www.aliexpress.com/item/1005009 ... f19cbm08xp and when plugged in as a second screen in Windows I can extract this EDID data from it:

Code:

Monitor  Model name............... LNU080014214  Manufacturer............. Acer  Plug and Play ID......... ACR0018  Serial number............ 537955803  Manufacture date......... 2012, ISO week 1  Filter driver............ None  -------------------------  EDID revision............ 1.3  Input signal type........ Digital  Color bit depth.......... Undefined  Display type............. RGB color  Screen size.............. Undefined or variable  Power management......... Not supported  Extension blocs.......... 1 (Unknown type)  -------------------------  DDC/CI................... Not supportedColor characteristics  Default color space...... Non-sRGB  Display gamma............ 2.20  Red chromaticity......... Rx 0.634 - Ry 0.354  Green chromaticity....... Gx 0.286 - Gy 0.620  Blue chromaticity........ Bx 0.138 - By 0.076  White point (default).... Wx 0.313 - Wy 0.328  Additional descriptors... NoneTiming characteristics  Horizontal scan range.... 35-40kHz  Vertical scan range...... 55-65Hz  Video bandwidth.......... 60MHz  CVT standard............. Not supported  GTF standard............. Not supported  Additional descriptors... None  Preferred timing......... No  Detailed timing #1....... 1024x600p at 60Hz     Modeline............... "1024x600" 51.800 1024 1072 1104 1370 600 603 609 630 +hsync +vsyncStandard timings supportedReport information  Date generated........... 22/11/2025  Software revision........ 2.91.0.1043  Data source.............. Real-time 0x0062  Operating system......... 10.0.26100.2Raw data  00,FF,FF,FF,FF,FF,FF,00,04,72,18,00,DB,8D,10,20,01,16,01,03,80,00,00,78,08,67,60,A2,5A,49,9E,23,  13,50,54,00,00,00,01,01,01,01,01,01,01,01,01,01,01,01,01,01,01,01,3C,14,00,5A,41,58,1E,20,30,20,  36,00,00,00,00,00,00,1E,00,00,00,10,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,FC,00,4C,  4E,55,30,38,30,30,31,34,32,31,34,0A,00,00,00,FD,00,37,41,23,28,06,00,0A,20,20,20,20,20,20,01,B2
If I install the 'normal' version of Raspberry Pi OS and follow this guide - https://www.raspberrypi.com/tutorials/h ... iosk-mode/ - this all works OK from a screen point of view (it fills up the screen immediately and I can change the orientation in the control panel) , but the (I presume) lack of memory means that it struggles to display even my simple test page (the TfL status board here - https://now.tfl.gov.uk/) and it results in extremely 'jumpy' animations.

This has lead me down the path of using the lite OS (which makes sense as all I am doing is running a couple of applications with no interactive versions), but I am now struggling, as I can't get the full screen to be used. I have these scripts/configs but none of them have worked:

/boot/firmware/config.txt - only alteration from default is the last line

Code:

# For more options and information see# http://rptl.io/configtxt# Some settings may impact device functionality. See link above for details# Uncomment some or all of these to enable the optional hardware interfaces#dtparam=i2c_arm=on#dtparam=i2s=on#dtparam=spi=on# Enable audio (loads snd_bcm2835)dtparam=audio=on# Additional overlays and parameters are documented# /boot/firmware/overlays/README# Automatically load overlays for detected camerascamera_auto_detect=1# Automatically load overlays for detected DSI displaysdisplay_auto_detect=1# Automatically load initramfs files, if foundauto_initramfs=1# Enable DRM VC4 V3D driverdtoverlay=vc4-kms-v3dmax_framebuffers=2# Don't have the firmware create an initial video= setting in cmdline.txt.# Use the kernel's default instead.disable_fw_kms_setup=1# Run in 64-bit modearm_64bit=1# Disable compensation for displays with overscandisable_overscan=1# Run as fast as firmware / board allowsarm_boost=1[cm4]# Enable host mode on the 2711 built-in XHCI USB controller.# This line should be removed if the legacy DWC2 controller is required# (e.g. for USB device mode) or if USB support is not required.otg_mode=1[cm5]dtoverlay=dwc2,dr_mode=host[all]#display_rotate=1
/home/pi/kiosk.sh

Code:

#!/bin/bash## Raspberry Pi OS Lite – Chromium Kiosk Launcher## Disable screen blanking / power savingxset -dpmsxset s offxset s noblank# Allow X to settlesleep 1# Rotate display to portrait# Now done in config#xrandr --output HDMI-1 --rotate left# Hide mouse cursor after 1 second of inactivityunclutter -idle 1 &# Start lightweight window manageropenbox-session &sleep 1# Launch Chromium in kiosk modechromium \  --noerrdialogs \  --disable-infobars \  --disable-translate \  --incognito \  --no-first-run \  --kiosk "http://example.com"
/home/pi/.bash_profile

Code:

# Start X only if not already runningif [ -z "$DISPLAY" ] && [ "$(tty)" = "/dev/tty1" ]; then    startx /home/pi/kiosk.sh --fi
/boot/firmware/cmdline.txt

Code:

console=serial0,115200 console=tty1 root=PARTUUID=a0b3806f-02 rootfstype=ext4 fsck.repair=yes rootwait cfg80211.ieee80211_regdom=GB #video=HDMI-A-1:1024x600M@60,rotate=90
As you can probably see, I've tried a few different approaches but for each one (trying just one thing at once) I get the following results:
With everything commented out - A landscape display using only about half the width of the screen - https://www.icloud.com/photos/#/icloudl ... 4S5NRlw/0/
With the bit at the end of the cmdline.txt enabled - same as above
With the config display_rotate enabled - same as above, but with an extra line on the right of the screen - https://www.icloud.com/photos/#/icloudl ... 6_9028w/0/
With the bit in the kisok.sh enabled - same as the last one, but now rotated to be portrait (so some progress at least!) - https://www.icloud.com/photos/#/icloudl ... yb32lwg/0/

One suggestion from ChatGPT was to run KMS Print which gave me:

Code:

Connector 0 (33) HDMI-A-1 (connected) Encoder 0 (32) TMDS Crtc 3 (95) 640x480@60.00 25.200 640/16/96/48/- 480/10/2/33/- 60 (60.00) Plane 3 (84) fb-id: 669 (crtcs: 3) 0,0 640x480 -> 0,0 640x480 (XR24 AR24 AB24 XB24 RG16 BG16 AR15 XR15 RG24 BG24 YU16 YV16 YU24 YV24 YU12 YV12 NV12 NV21 NV16 NV61 RGB8 BGR8 XR12 AR12 XB12 AB12 BX12 BA12 RX12 RA12) FB 669 640x480 XR24
Suggesting that the screen is stuck in 640*480 resolution and it did suggest that a custom EDID file might be the solution, but at this point it started hallucinating and giving me made up links, so not entirely sure how much to trust it on this one!

Thanks for reading all of this, and if there if anyone can suggest where to go next it would be appreciated!

Statistics: Posted by majesticbass — Sun Nov 23, 2025 1:04 am



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