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Raspberry Pi display issues

These can be caused by

  • The cable
  • The /boot/config.txt file
  • The monitor
  • Other issues

Names

NameMeaningExplanation
DMTDisplay Monitor TimingA VESA standard that lists display timings for various resolutions and screen sizes
CMAContiguous Memory AllocatorThe memory split between CPU and GPU is managed dynamically at runtime. This is not officially supported

Cable

Make sure you have a good cable
Use a

HDMI to HDMI

or

HDMI to DVI

cable as needed by the monitor
If the screen stays black check your cable
Cable info is available on hdmi to dvi cable

config.txt

Do NOT use

hdmi_safe=1

which sets:

hdmi_force_hotplug=1
hdmi_ignore_edid=0xa5000080
config_hdmi_boost=4
hdmi_group=2
hdmi_mode=4
disable_overscan=0
overscan_left=24
overscan_right=24
overscan_top=24
overscan_bottom=24

Set these manualy. For a Samsung Syncmaster 740B ( DVI 1280×1024@60Hz ) we used the settings below with succes
A “#” in front of a setting means: The default value will be used

SettingExplanation
hdmi_safe=0Set to 0: Safe mode off. Setting this to 1 uses “safe mode” settings to try to boot with maximum HDMI compatibility. See above for the individual settings
disable_overscan=1Set to 1 to disable
#overscan_left=24Turned off
#overscan_right=24Turned off
#overscan_top=24Turned off
#overscan_bottom=24Turned off
hdmi_group=2Set to 2 for DMT = Monitor; 1 for CEA = TV; 0 for Auto-detect from EDID
hdmi_mode=35Set to 35 for a 1280×1024@60Hz display. See link to config.txt explanation below for other settings
hdmi_drive=1Set to 1: Normal DVI mode (No sound); Set to 2: Normal HDMI mode (Sound will be sent if supported and enabled)
config_hdmi_boost=0Set the signal strength of the HDMI interface ( 0 - 7 )
hdmi_edid_file=0Setting this to 1 will cause the GPU to read EDID data from the edid.dat file, located in the boot partition, instead of reading it from the monitor. Since there is no /boot/edid.dat file it is set to 0
hdmi_ignore_edid=0xa5000080Ignore EDID/display data
hdmi_force_hotplug=1Set to 1: HDMI output mode will be used, even if no HDMI monitor is detected
hdmi_ignore_hotplug=0If set to 1: Composite output mode will be used, even if an HDMI monitor is detected

Source: config.txt explanation

Other ideas which might be helpful

Resolution issue

If the resolution is stuck at 640×480 it can be caused by the monitor not advertising the resolution. This can be caused by a bad edid configuration in the monitor. This might be solved by setting in

/boot/config.txt

this line

hdmi_force_hotplug=1

Useful commands

/opt/vc/bin/tvservice

Useful files

/boot/config.txt
edid.dat

Useful links: edid.dat file

Fixing EDID on DVI Monitors Showing No Signal When Windows Vista Boots
How to edid EDID data
How to get the display settings right on Raspberry Pi
EDID Data to fbset
HDMI Stuck at 640x480 wirtes:

My monitor doesn't supply EDID information to my Pi on the cable I use (cheap cable is probably the problem), so I connected it to a Linux PC via a VGA cable and dumped the EDID data from there. Then I saved that to /boot/edid.dat and added the option hdmi_edid_file=1 to config.txt

The monitor

Some monitors do not work at all. We did not get a Philps Brilliance 190P to work on DVI. It reported: “no signal”

Other issues

It can be that the Raspberry Pi itself is defective. We did not encounter this so far


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display_issues.txt · Last modified: 15-07-2016 16:50 by wim