RPi4 and Dual Displays

Hi,
I have a new Rpi4 and have connected 2 x 7" HDMI displays.

When I first booted up with both screens, it wouldn’t detect them after boot until I unplugged the HDMI cables and replugged them back in and then the GUI would display.

I then followed the instructions that came with the displays to install the 1024x600 driver and then it booted up ok, but only one display would be detected by the GUI.

I did notice however, that i have one python script that i can run that will run the Omxplayer and output video on a selected HDMI and this seems to work for both displays.

So my issue seems to be with the Raspian Buster GUI not detecting multiple displays after installing the display driver.

Any help would be appreciated.

Below is the config.txt file after the drivers were installed:

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
enable_uart=1

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
hdmi_group=2
hdmi_mode=1
hdmi_mode=87
hdmi_cvt 1024 600 60 6 0 0 0
dtoverlay=ads7846,cs=1,penirq=25,penirq_pull=2,speed=50000,keep_vref_on=0,swapxy=0,pmax=255,xohms=150,xmin=200,xmax=3900,ymin=200,ymax=3900
hdmi_drive=2
hdmi_force_hotplug=1
#max_usb_current=1

Thanks
Keith

Which 7" hdmi screens were you using? adafruit or our Little Bird 7" LCD’s?

It is the “Raspberry Pi 7inch GPIO Touch LCD”
one shown on spotpear.com/index.php/tutorials.

Did you mean this 7" lcd?

http://spotpear.com/index.php/spotpear-raspberry-pi-lcd/raspberry-pi-lcd-7-inch-hdmi-lcd-gpio-touch-800x480

I have the 7” 1024x600 lcds.

With both LCDs connected can you control the layout of the screens as in this blog?

Alternatively it could be a configuration problem in which cas you may have to change your config.txt display section as per this site:
https://www.raspberrypi.org/documentation/configuration/config-txt/video.md

Hi,
Still having no luck.

I have narrowed it down to this one line in the config.txt i think:

dtoverlay=

Below is the config.txt file. If i use the uncommented line below it will give me dual screens, but after booting i need to unplug the hdmi cables for about 5 seconds then replug them back in, otherwise i get two red screen saying “Not Support”.

If i use the other dtoverlay line currently commented out, it boots up ok for one display, but the other display isn’t detected by Raspian. However in a python program i have it will display a video on this display if i issue this commend “os.system(“omxplayer --display 7 -o local /home/pi/Progs/Scoreboard/test.mp4”)”

hdmi_mode=1
hdmi_mode=87
hdmi_cvt 1024 600 60 6 0 0 0
dtoverlay=vc4-fkms-v3d
#dtoverlay=ads7846,cs=1,penirq=25,penirq_pull=2,speed=50000,keep_vref_on=0,swapxy=0,pmax=255,xohms=150,xmin=200,xmax=3900,ymin=200,ymax=3900
hdmi_drive=2
hdmi_force_hotplug=1

Keith

I have something for you to try, would you be able to goto your terminal once you have a display up and running of course and type the following command:

DISPLAY=:0 xrandr
then either send though a screen shot or copy and paste the output in a reply

it will help me figure out what is going on, i suspect it could be a configuration issue and or EEID problem

Similar to what is going on in this thread
https://www.raspberrypi.org/forums/viewtopic.php?t=245527\