On Sun, Jul 05, 2020 at 09:18:55PM +0100, testing999...@zohomail.eu wrote:
> i can't get any u-boot serial output from miniroot67.fs on a raspberry
> pi 3. i'm using a 'FTDI232' which cost ~$4 - USB to 3.3V jumper
> cables, connecting TX to RX and vice versa on GPIO header.
>
> my serial console setup works without issue with a pi 1 and a pi 3,
> running raspbian, with:
> $ screen /dev/ttyUSB0 115200
> i had to add 'enable_uart=1' to /boot/config.txt before with console
> became accessible, on the pi 3.
>
> i tried mounting the partitions after dd'ing miniroot67.fs and
> looking for some text files to edit, but there were only binaries
>
> any ideas? i can only think of trying older miniroots or snapshots
> next. thanks
The arm64 miniroot contains a fat filesystem with raspberry pi firmware,
config.txt and rpi_3 u-boot. The config.txt already has serial enabled
(with pl011 uart):
arm_64bit=1
enable_uart=1
dtoverlay=disable-bt
kernel=u-boot.bin
You can force the firmware stage which runs before u-boot to output on
serial by modifying bootcode.bin as described at the end of
https://www.raspberrypi.org/documentation/hardware/raspberrypi/bootmodes/README.md
If you try miniroot67.img from a snapshot you'll get a more recent
version of u-boot. May be worth trying.
