Nicholas.Tomlin
Posts: 2
Joined: Thu Jul 21, 2016 1:11 pm

HDMI Display Settings - 800x480

Thu Jul 21, 2016 1:34 pm

hdmi trickery, after 10 goes I got it going properly.

Firstly - only use the vertical resolution to determine what you need to do, so for a hdmi screen with a 800x480 resolution in 7¨ I selected 848 x 480 which is DMT mode 14.
So I set in config.txt [below] that hdmi_group=2 and hdmi_mode=14 by unhashing them.
Then set the right margin overscan to be smaller by 48 which brought the right margin to the left by 48 pixels, now the screen displays properly.

If you mess it up and the pi won´t display, pull the sd card out and edit it using any other computer by mounting the boot volume and then using a simple text editor to change the config.txt file.

What I changed in //boot/config.txt to make a HDMI 800x480 screen work.

//boot/config.txt:

# For more options and information see
# http://www.raspberrypi.org/documentatio ... fig-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=-96
overscan_right=48 #this was unhashed and 48 selected
# overscan_top=-32
# overscan_bottom=128

# uncomment to force a console size. By default it will be display's size minus
# overscan.
#framebuffer_width=400
#framebuffer_height=240

# 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=2 #this was unhashed and 2 selected
hdmi_mode=14 #this was unhashed and 14 selected

# 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=on

# NOOBS Auto-generated Settings:
hdmi_force_hotplug=1
start_x=1
gpu_mem=128

User avatar
liudr
Posts: 687
Joined: Sat Jun 01, 2013 12:11 am
Location: Central MN, USA
Contact: Website

Re: HDMI Display Settings - 800x480

Thu Jul 21, 2016 10:49 pm

I am using a custom hdmi mode and it works well.
https://learn.adafruit.com/adafruit-5-8 ... -pi-config
Arduino data loggers, user interface, printed circuit board designer since 2009, RPI 3B 2B 2B Zero Jessie, assembly/C/C++/java/python programmer since the 80's

RAZERZ
Posts: 57
Joined: Mon Jun 13, 2016 4:56 pm

Re: HDMI Display Settings - 800x480

Sun Jul 24, 2016 11:58 am

I think you could have uncommented framebuffer and put the screen resolutions there. I used to do it before i got my hdmi to vga.
Raspberry pi 3 set up as desktop with raspbian.
I guess you can say I am not newbie with linux but I am not a master at it either.
I will always try to help you as much as I can because I know how hard it is to run into problems :D

sarrasmith
Posts: 3
Joined: Mon Aug 01, 2016 7:15 pm

Re: HDMI Display Settings - 800x480

Mon Aug 01, 2016 7:33 pm

Thank you for this. I was having a hell of a time getting my Adafruit HDMI 5" Display Backpack screen working. The settings that Adafruit suggested were giving me this weird, interlaced, incorrectly decoded output thing. Your settings work perfectly.

Here's the screen if anyone else runs into this problem: https://www.adafruit.com/product/2232. Hopefully people in my situation can find this post.

Nicholas.Tomlin
Posts: 2
Joined: Thu Jul 21, 2016 1:11 pm

Re: HDMI Display Settings - 800x480

Tue Aug 02, 2016 3:42 am

RAZERZ wrote:I think you could have uncommented framebuffer and put the screen resolutions there. I used to do it before i got my hdmi to vga.

Razerz - tried that - didn't work, part of the 9 failures on the way to success.

RAZERZ
Posts: 57
Joined: Mon Jun 13, 2016 4:56 pm

Re: HDMI Display Settings - 800x480

Tue Aug 02, 2016 3:00 pm

Nicholas.Tomlin wrote:
RAZERZ wrote:I think you could have uncommented framebuffer and put the screen resolutions there. I used to do it before i got my hdmi to vga.

Razerz - tried that - didn't work, part of the 9 failures on the way to success.
Hmm, have you set hdmi_drive in /boot/config.txt? Just curious if it is uncommented and what number it is at.
Raspberry pi 3 set up as desktop with raspbian.
I guess you can say I am not newbie with linux but I am not a master at it either.
I will always try to help you as much as I can because I know how hard it is to run into problems :D

tito-t
Posts: 298
Joined: Thu Jan 07, 2016 5:14 pm

Re: HDMI Display Settings - 800x480

Tue Aug 02, 2016 6:53 pm

it would be nice if there was a GUI menu to set up automatic default or customized screen resolutions - and a failsafe standard mode which is automatically chosen if customized settings once failed (perhaps like in Windows) - or perhaps could be chosen by a hotkey combination (ctrl+alt+print, ctrl+alt+roll, ctrl+alt+pgUp, ctrl+alt+ins, or whatever) if the screen keeps black. I often have to force 800x480 or 1024x600 when the TFT is not auto-detected and it's annoying if one has to patch config files on boot partitions externally and manually on Windows PCs in case of emergancy.
- Tim

davelawrence
Posts: 12
Joined: Thu Dec 10, 2015 5:14 pm

Re: HDMI Display Settings - 800x480

Fri Aug 17, 2018 10:47 pm

Just wanted to thank liudr for https://www.raspberrypi.org/forums/post ... #pr1013178 which solved my problem of trying to VNC to a "headless" RPi

In a different hardware build that had the official LCD attached and therefore produced an 800x480 display. In a more embedded build, without the screen attached it defaulted to 720x480, but this hdmi "force" fixed the screen size for my (kivy) app.

(if anyone else gets similarly stuck, it was also necessary to modprobe evdev (or include in /etc/modules) to provide mount/input/click support so the VNC server would work and pass clicks to the app)

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