If you take a look at notro's fbtft documentation, specifically the the information about using your display as a Boot Console, there is some information about attaching displays to different
There is additional kernel documentation that describes mapping specific devices to specific
This is an interesting option. It tells which driver gets mapped to
which console. The value '0123' is a sequence that gets repeated until
the total length is 64 which is the number of consoles available. In
the above example, it is expanded to 012301230123... and the mapping
tty | 1 2 3 4 5 6 7 8 9 ...
fb | 0 1 2 3 0 1 2 3 0 ...
('cat /proc/fb' should tell you what the fb numbers are)
One side effect that may be useful is using a map value that exceeds
the number of loaded fb drivers. For example, if only one driver is
available, fb0, adding fbcon=map:1 tells fbcon not to take over the
Later on, when you want to map the console the to the framebuffer
device, you can use the con2fbmap utility.
By setting your
dtoverlay device to a specific
tty, you can see if you can switch between this device and your HDMI device. Here is a
# See /boot/overlays/README for all available options
initramfs initramfs-linux.img followkernel
hdmi_cvt 1024 600 60 6 0 0 0
And an example of
boot/cmdline.txt. Focus on
root=/dev/mapper/pi-root cryptdevice=/dev/mmcblk0p3:pi-root:allow-discards rootfstype=ext4 rw rootwait fbcon=map:10 console=ttyAMA0,115200 console=tty1 selinux=0 plymouth.enable=0 smsc95xx.turbo_mode=N dwc_otg.lpm_enable=0 kgdboc=ttyAMA0,115200 elevator=noop logo.nologo
Now that this is set up with the first overlay being assigned to the first
tty, and you've restarted, the boot log/console should show up on your
dtoverlay display after a short time. The other display (HDMI) becomes the next
tty, so in this case, the second (
Because they are on separate
ttys, you will have to switch between them to input and potentially see the
tty with CTRL+ALT+F1 and CTRL+ALT+F1
- notro's fbtft documentation is the wiki for the repository before it was brought upstream. This means that some of the information is outdated, but this repo shows the mechanics behind
dtoverlay and provides helpful information even today.