When I plugged my SD card (which worked flawlessly on my “older Raspberry PI” model) into my brand new “Raspberry PI 4” it simply didn’t boot. (My base image was a piaware Raspbian download from flightaware.) This is how I fixed that.
Backup your SD card beforehand, for instruction click here.
First we need to download the newest firmware as the previous one was not built with Raspberry PI 4 support.
https://github.com/raspberrypi/firmware/
Copy all the files in “firmware-master/boot/” onto your SD card and replace all the old files.
Next we need to edit cmdline.txt
Replace it’s content with this
dwc_otg.fiq_fix_enable=2 console=ttyAMA0,115200 kgdboc=ttyAMA0,115200 console=tty1 root=/dev/mmcblk0p2 rootfstype=ext4 rootwait rootflags=noload net.ifnames=0It should boot again normally…