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I use a RPi3 with the Recalbox OS for some retrogaming. And I want to use the official 7" DPI monitor when it's portable, and the HDMI when I connect it to the TV. I tried plugging the HDMI cable in, and it registers and switches channel, but the picture is just black on the tv and the 7" display is still working.
Can I somehow make this work automatically, without changing the config.txt file every time I want to change output? Or is it possible to mirror the DPI output to the HDMI output?
As far as I remember, you need hdmi_force_hotplug=1 in your config.txt if the HDMI screen is not connected at boot time. Otherwise, if you start without an HDMI screen but later connect it, it will not work until you reboot.
