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NixOS
Issues with connecting nixos-21.05 on a raspberry-pi-4 to multiple LG monitors:
Hello there, The pi connects fine to a single LG monitor, xrandr detects it, and I'm able to do customizations with it(except, I'm unable to change brightness with xrandr, so I have to manually press the monitors buttons to set the brightness). But, whenever I try to connected the pi to a 2nd LG monitor(which is the exact same model), and it stays stuck in the rainbow screen? And xrandr does not detect the 2nd monitor either? I enabled home-manager's autorandr option, but that does not fix this issue either? I'm posting this issue here, because I'm not sure if it's a hardware problem. Also I haven't messed with the pi's bootloader config.txt file, so I don't know if that would fix this issue. If you could at least give some tips on how to troubleshoot this issue. Thanks in advance for helping fix this issue.
https://nix.dev/tutorials/installing-nixos-on-a-raspberry-pi
https://www.reddit.com/r/NixOS/comments/o5cj36/issues_getting_multiple_monitors_working_with_a/
Ok, I've made some progress, I'm guessing that I'm at the point where I need to tweak the pi's bootloader, but I'm hesitatant to make changes there, because I don't want to brick the pi, making it unusable.
https://www.reddit.com/r/NixOS/comments/o5cj36/issues_getting_multiple_monitors_working_with_a/h2vx9jt/?context=3
Here's the same issue with more information:
https://www.reddit.com/r/NixOS/comments/o82k11/nixospi4_issues_trying_to_get_a_dualdisplay_setup/
Ok, I've made some progress, I'm guessing that I'm at the point where I need to tweak the pi's bootloader, but I'm hesitatant to make changes there, because I don't want to brick the pi, making it unusable.
https://www.reddit.com/r/NixOS/comments/o5cj36/issues_getting_multiple_monitors_working_with_a/h2vx9jt/?context=3
It is unlikely that this change would be permanent if you just edit some text files, you can mount the sdcard on a different machine and change it back.
@Mic92 , the changes do seem to be permanent when I mount and configure the config.txt file directly on the pi.
@Mic92 , I'm able to get nixos on pi-4 to render to two 2k monitors, but ran into more issues: https://github.com/NixOS/nixos-hardware/issues/282
https://gist.github.com/donrestarone/5edfee56f2da086bc173c25b3d6fb225 I've had the best luck with this: #fix for rpi 4 models with dual hdmi hdmi_force_hotplug:0=1 hdmi_force_hotplug:1=1 hdmi_drive=2