Enable UART_E on Khadas VIM4

[cpickart]

Hi all,

in the Khadas images for the VIM4 uart can be enabled via device tree overlay.
This enables the device /dev/ttyS4.
As far as I understood, Coreelec’s kernel does not support overlays, so I tried myself
by decompiling the device tree and enabling node serial@fe080000 by setting status = “okay”.
This did not work, and to be frank, I have no clue about what I am doing.

Can someone advice me what to change in the device tree to get up that additional serial connection?

Thanks in advance,

Christoph

[Portisch]

You will need to add this to DT source:

&uart_E {
	status = "okay";
};

Or set status okay by fdtput on existing dtb.img.

The pins are default used for TSIN so I am not sure if there will be a issue.

[cpickart]

Hi,

I tried
fdtput /flash/dtb.img "&uart_E" status "okay"
Not sure whether it is correct but it gives me
Error at '&uart_E': FDT_ERR_BADPATH
There is no node uart_E or &uart_E in the device tree. However, in the khadas device tree uart_E occurs in the __symbols__ section and refers to /soc/serial@fe080000. So I guess that uart_E is an alias
for that path.
I have already changed node serial@fe080000 to status = "okay" but that did not work.

Just to be sure: I compiled the device tree to /flash/dtb.img. Is that correct?

Christoph

[cpickart]

Hi,

I somehow achieved it. Just in case someone else also needs it:
It involves two changes in the device tree:

In node uart_e change
groups = "uart_e_tx\0uart_e_rx\0uart_e_cts\0uart_e_rts";
to
groups = "uart_e_tx\0uart_e_rx";

In node serial@fe080000 change

status = "disabled";
to
status = "okay";

The device /dev/ttyS4 appears then after reboot. I additionally had to configure it with

stty -F /dev/ttyS4 19200 sane

to make the arduino understand.

Christoph