Rpi 4 w/ official 7in touch screen no hdmi out

lucent88

Raspberry pi4 - 4gb
Os - Retropie 4.7.1

I have a retro pi set up with the official touch screen connected to the Pi's display port and gpio.

When I connect with HDMI and boot it shows the first 3 second boot screen then loses signal. I've followed several different guides and suggestions I've found on the forums to no avail.
I've even re-flashed my sd card to see if that was the issue

Is there something i can try that's different, or should i buy a new sd card and try rebuilding?

Thank you

mitu

@lucent88 Is the display working if you flash the normal Raspberry Pi OS (with Desktop) image ?

lucent88

@mitu
i have not tried that, i will do so now. I didnt even think of that , thank goodness i store all roms and saves on my thumb drive .

lucent88

@mitu
ok got the raspberry pi os flashed and set up, it shows also shows a brief moment of the boot screen then nothing

mitu

So you have both the 7'' touch screen connected via DSI (Display interface) and the HDMI screen - you get image on the touch screen, but not on the HDMI ? If yes, I think that's normal

In some situations, it allows for the use of both the HDMI and LCD displays at the same time (this requires software support).

The only mention of using both simultaneously is at https://www.raspberrypi.org/documentation/hardware/display/troubleshooting.md

At the moment you can't use HDMI and the LCD together in the X desktop, but you can send the output of certain applications to one screen or the other.

Omxplayer is one example. It has been modified to enable secondary display output
...

lucent88

@mitu yes thats the setup, ok so if thats normal, and i dont get any hdmi, does retropie have a download or something that i can add so i can switch between the screens. for when im on the go or im at home, so i can use it with my tv?

mitu

@lucent88 You can try a config.txt setting to disable the DSI when a connected HDMI display is detected (see this issue).

Add the following lines at the end of the config.txt file located on the /boot partition:

[EDID=*]
ignore_lcd=1

then reboot and see if it works.

lucent88

@mitu Will do im doing my last flash of the sd card, and once i get tthings booted and running i will report back!

lucent88

@mitu

Omg omg it worked, it worked, 2 days of busting google and configs and it worked. I should have came here first! thank you so much!!!!

is there a way to make it detect on plug and unplug or do i just need to reboot, every time?

mitu

@lucent88 said in Rpi 4 w/ official 7in touch screen no hdmi out:

is there a way to make it detect on plug and unplug or do i just need to reboot, every time?

With the config.txt approach, yes, a reboot is needed since the configuration is only applied on boot. Not sure if there is a way to enable it at runtime - maybe for the HDMI port.