How can I use the UART ports on Zero 3W?

[iqakb]

Can anyone help me in setting up the UART ports on Zero 3W specifically the GPIO0_D1 and GPIO0_D0 ports? I'm using Ubuntu 22.04 version 5.10.0-1012-rockchip build.

This is my /etc/default/u-boot configuration:

## /etc/default/u-boot - configuration file for u-boot-update(8)
U_BOOT_UPDATE="true"
#U_BOOT_ALTERNATIVES="default recovery"
#U_BOOT_DEFAULT="l0"
#U_BOOT_PROMPT="1"
#U_BOOT_ENTRIES="all"
#U_BOOT_MENU_LABEL="Debian GNU/Linux"
#U_BOOT_PARAMETERS="ro earlycon"
#U_BOOT_ROOT=""
#U_BOOT_TIMEOUT="50"
#U_BOOT_FDT=""
#U_BOOT_FDT_DIR="/lib/firmware/"
U_BOOT_FDT_OVERLAYS="rk3568-disable-fiq-debugger.dtbo rk3568-uart2-m0.dtbo"
U_BOOT_FDT_OVERLAYS_DIR="/lib/firmware/$(uname -r)/device-tree/rockchip/overlay"
#U_BOOT_SYNC_DTBS="false


I have ran sudo u-boot-update then rebooted the board, yet it still didn't work. I was able to change the USB OTG port into a host through modifying the /etc/default/u-boot file, so I'm a bit uncertain on what I did wrong in setting up the UART port.

[ErikParkerrr]

Did you figure this out?

Thanks

[iqakb]

No, I used a USB hub instead for my application back then

[ErikParkerrr]

No, I used a USB hub instead for my application back then

I beleive your issue was uboot cannot do $(uname -r). Mine is hardcoded and worked immediately. To all future people who find this:

U_BOOT_FDT_OVERLAYS_DIR="/lib/firmware/$(uname -r)/device-tree/rockchip/overlay"

must be hard coded to the exact folder path.

Also, for future people, there is an overlay to make the second usb port work in host mode if you need that instead of a usb hub.

Cheers