Rockpi4/dev/use-uart2-as-application-uart
ROCK Pi 4 > Development > Use UART2 as Application UART
OUTDATED
The content below is out of date. User should use rsetup to enable UART overlay instead.
The original content is kept for historical purpose.
Description
If you want to use uart with Kernel > 5.10 in ROCK Pi 4. You can follow these steps.
Install essential package
sudo apt-get install -y rockpi4-dtbo
UART
Modify file /boot/hw_intfc.conf. Set "on" to enable the optional hardware interfaces while set "off" to disable.
intfc:uart2=on intfc:uart4=on
And add "#" to line "intfc:dtoverlay=console-on-ttyS2"
#intfc:dtoverlay=console-on-ttyS2 #intfc:dtoverlay=console-on-ttyS4
by now, the uart2 can still be used as a debug port with system log. If you don't want to output kernel messages, you can disable it as follow.
Modify file /boot/extlinux/extlinux.conf.
append earlyprintk console=ttyFIQ0,1500000n8 rw init=/sbin/init rootfstype=ext4 rootwait root=UUID=8650cdca-49b0-4431-9667-5c639f6bab89 console=ttyS2,1500000n8
Delete strings console=ttyFIQ0,1500000n8 and console=ttyS2,1500000n8 in this line.
append earlyprintk rw init=/sbin/init rootfstype=ext4 rootwait root=UUID=8650cdca-49b0-4431-9667-5c639f6bab89