VIM3 Activate 3 UART


I am using VIM3 - Android 9.

I’ve read one user on this forum being able to activate uarts (UARTA, UARTB, UARTC) on the 40 pins header.

It’s no problem for us to recompile the android image, but could you please give details on the pins number for each possible UART (if 4 UART are possible, please tell) ? And what modifications exactly are required before recompiling ?

Thank you!


Hello and welcome,
I believe you were referring to @davemf as he was able to add the extra UART, I am sure he will be able to help you modify it, but regarding a 4th UART, I am not sure if the hardware can support that, and even if it could it might not be in the GPIO…, @Terry might also be able to help you…

all the best,

UART0 - ttyS3 works by default on vim3
UATR1 - it is Linux kernel debug port. It’s work too.


Hi @davemf I’ve installed latest ubuntu desktop from here but no ttyS3 is inside on my /dev folder. I’ve also try to use approach found in this how to without success.

Any suggestions about ? I’m not able to communicate with uart using ttyS0 or ttyS1.

Thanks in advance.

I used android only. I don’t know about ubuntu.

Hi All,
I also not able to enable UARTC on by board VIM3 Pro with latest Ubuntu release from Khadas.

How can I enable uart?


Hello, please check docs:

Yes, I’ve include this line into the “/boot/env.txt”

#Enable UART3
overlays=uart3 pwm_ao_a pwm_f i2c0

# Specify the initial console log level (0~8)


And in console I see (I’ve disable Linux cosole for UART0):
khadas@Khadas:~$ ls -ltrh /dev/ttyS*
crw-rw---- 1 root dialout 236, 0 Mar 23 13:45 /dev/ttyS0
crw-rw---- 1 root dialout 236, 1 Mar 23 13:45 /dev/ttyS1

And here there is no ttyS3.
And when I access ttyS1, I also can’t send any data.


have you installed minicom ?

On PC side I have other application.
But I don’t see the signals even with logic analyzer.
With Linux_RX/TX I see. It’s working well.
With UARTC it’s not.

maybe you are connecting to the wrong port, please verify that it is the right port…

I’m sure.
I have two available ports:
crw-rw---- 1 root dialout 236, 0 Mar 23 13:45 /dev/ttyS0
crw-rw---- 1 root dialout 236, 1 Mar 23 13:45 /dev/ttyS1

S0 is working correct, S1 is not working. And I have no S3.


I also have exactly problem.
How did you fix it?

I didn’t fix it.
It still exist.

um…then, How do you use UART?

I’ve disable Linux uart as linux, and use it as normal one.

1 Like

I also have this problem, can someone fix it?

Hello Dmitry,
Could you tell me how to activate the Linux debug port/uart as a normal UART?


I have same problem, How to fix?