If you have bought a Raspberry Pi 3 with a case and doesn’t have a serial port, you might face an issues to debug or observe kernel booting, but there in an option with which you can enable the display console on RPi3.
In this post, we will assume you have a SD card with RPi image flashed on it.
- Plug the SD card to PC.
- check where /boot partition of RPi is mounted, using “mount” command, you might see something like below,/dev/sdb1 on /media/user/raspberrypi type vfat (rw,nosuid,nodev,uid=1000,gid=1000,shortname=mixed,dmask=0077,utf8=1,showexec,flush,uhelper=udisks2)
/dev/sdb2 on /media/user/1752ce87-99af-4b4a-8d34-39ca7a21a78e type ext3 (rw,nosuid,nodev,uhelper=udisks2) - vim /media/user/raspberrypi/cmdline.txt
- append following line to cmdline.txt and save.
console=tty1 fbcon=map:10 fbcon=font:VGA8x8 - so you might now have cmdline.txt something like below,
dwc_otg.lpm_enable=0 console=serial0,115200 console=tty1 root=/dev/mmcblk0p2 rootfstype=ext4 rootwait debug fbcon=map:10 fbcon=font:VGA8x8 - put the SD card to RPi3 and boot, you should see the kernel debug messages now on HDMI display.