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How to enable serial console?

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sereneguy
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Joined: 2021-08-19 01:02

How to enable serial console?

#1 Post by sereneguy »

Hi,

I am new to Debian, but I have been using some other distros in the past (Arch, Ubuntu, Raspberry Pi), long time ago.
I want to enable serial console in Debian 10 (it's running on SBC - ASUS TinkerBoard).

My understanding is that I need to find the boot config file, which is in /boot/config-*
However, I only saw one file: /boot/config.txt

I enabled the uart interface, and also added console=tty1,115200n8 - still doesn't work.

Could someone give me some pointers?
Thanks in advance.

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Re: How to enable serial console?

#2 Post by peter_irich »

Far example, man stty, man cu. stty is for tweaking, cu for input/output.

Peter.

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Re: How to enable serial console?

#3 Post by Aki »

@sereneguy:

Is this [1] your board ?

According to what is reported at [2]:
UART
Connecting a serial adapter to UART3 of the Asus Tinker-Board

The default serial console is UART3, 115200 baud, 8N1 (8bit, no parity, 1 stop bit), no software flow control (Xon/Xoff), no hardware flow control.

A "Prolific Technology, Inc. PL2303 Serial Port (067b:2303)" USB adapter can be used.

The relevant kernel parameter is console=ttyS3,115200n8
Have you tried to connect to the appropriate GPIO pins using a four pin serial-to-usb adapter ?

Have you configured the kernel boot parameter "console=ttyS3,115200n8" ?

[1] https://www.asus.com/networking-iot-ser ... ker-board/
[2] https://tinkerboarding.co.uk/wiki/index.php/Hardware
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sereneguy
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Re: How to enable serial console?

#4 Post by sereneguy »

Aki wrote: 2021-08-19 08:31 @sereneguy:

Is this [1] your board ?

According to what is reported at [2]:
UART
Connecting a serial adapter to UART3 of the Asus Tinker-Board

The default serial console is UART3, 115200 baud, 8N1 (8bit, no parity, 1 stop bit), no software flow control (Xon/Xoff), no hardware flow control.

A "Prolific Technology, Inc. PL2303 Serial Port (067b:2303)" USB adapter can be used.

The relevant kernel parameter is console=ttyS3,115200n8
Have you tried to connect to the appropriate GPIO pins using a four pin serial-to-usb adapter ?

Have you configured the kernel boot parameter "console=ttyS3,115200n8" ?

[1] https://www.asus.com/networking-iot-ser ... ker-board/
[2] https://tinkerboarding.co.uk/wiki/index.php/Hardware
Hi Aki,

Yes, it's my board. It's the 2S model, which is fairly new, and many information I saw aren't applicable to this model.

Yes, I use FTDI, and Putty on the PC side. I tested my setup with my Pi (to ensure it works).

My question is, how to modify kernel boot parameter. I modified /boot/config.txt, and added "console=tty1,115200n8".
I am not sure if config.txt is the right place, that's why I posted this.

sereneguy
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Re: How to enable serial console?

#5 Post by sereneguy »

peter_irich wrote: 2021-08-19 04:17 Far example, man stty, man cu. stty is for tweaking, cu for input/output.

Peter.
Hi Peter, I tried to modify the kernel boot param.

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Re: How to enable serial console?

#6 Post by Aki »

@sereneguy:
sereneguy wrote: 2021-08-20 02:15 Hi Aki,
[..] My question is, how to modify kernel boot parameter. I modified /boot/config.txt, and added "console=tty1,115200n8". I am not sure if config.txt is the right place, that's why I posted this.
According to the documentation in "Thinker board wiki" [1], the section "console log setup" (see [2]) explains how to do it and it reports:
console log setup
For the Debian image before V2.0.4 and Android image before android_20171115_v13.12.0.43
Please reference https://tinkerboarding.co.uk/wiki/image ... _1.0.3.pdf
For the Debian image after V2.0.5 and Android image after android_20180206_v13.13.0.74
Please reference https://tinkerboarding.co.uk/wiki/image ... _1.0.6.pdf
In both cases (Debian image before V2.0.4 and Debian image after V2.0.5), it is documented to modify the extlinux.conf file (in extlinux directory on the SD card where the Debian operating system is stored) to configure the kernel console parameter.

Hope that it helps.

[1] https://tinkerboarding.co.uk/wiki/index.php/Hardware
[2] https://tinkerboarding.co.uk/wiki/index ... _log_setup
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sereneguy
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Re: How to enable serial console?

#7 Post by sereneguy »

Aki wrote: 2021-08-20 08:17 @sereneguy:
sereneguy wrote: 2021-08-20 02:15 Hi Aki,
[..] My question is, how to modify kernel boot parameter. I modified /boot/config.txt, and added "console=tty1,115200n8". I am not sure if config.txt is the right place, that's why I posted this.
According to the documentation in "Thinker board wiki" [1], the section "console log setup" (see [2]) explains how to do it and it reports:
console log setup
For the Debian image before V2.0.4 and Android image before android_20171115_v13.12.0.43
Please reference https://tinkerboarding.co.uk/wiki/image ... _1.0.3.pdf
For the Debian image after V2.0.5 and Android image after android_20180206_v13.13.0.74
Please reference https://tinkerboarding.co.uk/wiki/image ... _1.0.6.pdf
In both cases (Debian image before V2.0.4 and Debian image after V2.0.5), it is documented to modify the extlinux.conf file (in extlinux directory on the SD card where the Debian operating system is stored) to configure the kernel console parameter.

Hope that it helps.

[1] https://tinkerboarding.co.uk/wiki/index.php/Hardware
[2] https://tinkerboarding.co.uk/wiki/index ... _log_setup
Hi Aki,

Yes, I saw/reviewed those references before. The problem is, none of them applies to TinkerBoard 2S that I have right now.
The only Debian image available for my board are only Debian 9 (V1.0.7) and Debian 10 (V2.0.0):
  • None of them has extlinux.conf like what the instruction said
  • None of them has USB storage when I connected the board to Windows - no accessible partition visible from Windows (I used terminal to access /boot and only saw config.txt)
That's why I didn't know where to find kernel boot parameter.
It's like for this new board, TinkerBoard 2S, they changed the Debian image radically, and there is no documentation or discussion for this particular board yet.

Any other idea?

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Re: How to enable serial console?

#8 Post by Aki »

Hello,

To better understand, I downloaded the SD disk image from ASUS thinker site, called Tinker_Board_2-Debian-Buster-v2.0.0-20210413.zip: is the image that are you using ?

This zip file contains the following image file:

Code: Select all

Tinker_Board_2-Debian-Buster-v2.0.0-20210413.img
This Tinker_Board_2-Debian-Buster-v2.0.0-20210413.img image file contains the following partitions:

Code: Select all

$ mmls Tinker_Board_2-Debian-Buster-v2.0.0-20210413.img 
GUID Partition Table (EFI)
Offset Sector: 0
Units are in 512-byte sectors

      Slot      Start        End          Length       Description
000:  Meta      0000000000   0000000000   0000000001   Safety Table
001:  -------   0000000000   0000016383   0000016384   Unallocated
002:  Meta      0000000001   0000000001   0000000001   GPT Header
003:  Meta      0000000002   0000000033   0000000032   Partition Table
004:  000       0000016384   0000024575   0000008192   uboot
005:  001       0000024576   0000032767   0000008192   trust
006:  002       0000032768   0000040959   0000008192   misc
007:  003       0000040960   0000106495   0000065536   boot
008:  004       0000106496   0000172031   0000065536   recovery
009:  005       0000172032   0000237567   0000065536   backup
010:  006       0000237568   0000368639   0000131072   userdata
011:  007       0000368640   0008056567   0007687928   rootfs

After transferring the image to the SD, Debian recognize two partitions (named "userdata" and "rootfs") in it.

These are the contents of "roofs":

Code: Select all

$ ls  -l 9d8e2803-1083-4cb6-993f-1e1c3f83b6ac
total 23660
drwxr-xr-x   2 root root    4096 13 apr 05.30 bin
drwxr-xr-x   2 root root    4096 22 nov  2020 boot
drwxr-xr-x   4 root root    4096 19 gen  2021 dev
drwxr-xr-x 110 root root    4096 13 apr 05.50 etc
drwxr-xr-x   3 root root    4096 19 gen  2021 home
drwxr-xr-x  16 root root    4096 13 apr 05.50 lib
drwx------   2 root root   16384 13 apr 05.50 lost+found
-rw-r--r--   1 root root 4547234 19 gen  2021 md5sum.txt
drwxr-xr-x   2 root root    4096 19 gen  2021 media
drwxr-xr-x   2 root root    4096 19 gen  2021 mnt
drwxr-xr-x   2 root root    4096 19 gen  2021 opt
drwxr-xr-x  15 root root    4096 13 apr 05.28 packages
drwxr-xr-x   2 root root    4096 22 nov  2020 proc
-rw-r--r--   1 root root 9789440 19 gen  2021 qemu_gdk-pixbuf-query-loaders_20210119-145338_2682.core
-rw-r--r--   1 root root 9789440 19 gen  2021 qemu_gdk-pixbuf-query-loaders_20210119-145653_7472.core
drwx------   2 root root    4096 19 gen  2021 root
drwxr-xr-x   7 root root    4096 19 gen  2021 run
drwxr-xr-x   2 root root    4096 19 gen  2021 sbin
drwxr-xr-x   2 root root    4096 19 gen  2021 srv
drwxr-xr-x   2 root root    4096 22 nov  2020 sys
drwxr-xr-x   4 root root    4096 13 apr 05.29 system
drwxrwxrwt   2 root root    4096 13 apr 05.50 tmp
drwxr-xr-x  10 root root    4096 19 gen  2021 usr
drwxr-xr-x  11 root root    4096 19 gen  2021 var
These are the contents of "userdata":

Code: Select all

$ ls -l c42c86b8-2a11-423a-bb32-17b59d0fe66a
total 286
-rwxrwxr-x 1 root root  87402  8 mar 03.28 200frames_count.h264
-rwxrwxr-x 1 root root  81582  8 mar 03.28 belle-nuit-testchart-1080p.png
-rw-rw-r-- 1 root root     58  8 mar 03.28 cmdline.txt
-rw-rw-r-- 1 root root   1550  8 mar 03.28 config.txt
drwx------ 2 root root  12288 13 apr 06.09 lost+found
drwxrwxr-x 2 root root   2048 13 apr 06.09 overlays
-rwxrwxr-x 1 root root 101760  8 mar 03.28 piano2-CoolEdit.mp3
The config.txt probably should be updated to enable the specific used UART.
The cmdline.txt perhaps contains the boot kernel parameters.
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sereneguy
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Re: How to enable serial console?

#9 Post by sereneguy »

Hi Aki,

Yes, I already modified config.txt as I mentioned in my first post.
I just added "console=ttyS1,115200n8" to cmdline.txt too, still not working.

Btw, the cmdline.txt was empty, it has that line I added.

Did I miss something?

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Re: How to enable serial console?

#10 Post by Aki »

Hello,

The config.txt should be configured according to [1] as shown in page 11 to activate the UART. Therefore, the configuration "console=ttyS1,115200n8" does not apply to config.txt.

Configure config.txt to activate the UART and reboot the board. After the boot, the board UART should be active,

[1] https://tinker-board.asus.com/images/do ... tarted.pdf
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Re: How to enable serial console?

#11 Post by sereneguy »

Aki wrote: 2021-08-21 09:49 Hello,

The config.txt should be configured according to [1] as shown in page 11 to activate the UART. Therefore, the configuration "console=ttyS1,115200n8" does not apply to config.txt.

Configure config.txt to activate the UART and reboot the board. After the boot, the board UART should be active,

[1] https://tinker-board.asus.com/images/do ... tarted.pdf
Thank you so much. I never thought they would put information in other board (Edge R).
So, yes, I have UART1 works now.

Even though the UART1 works (I can write application to send and receive data via UART - by initializing it via periphery), but the console still doesn't work on UART1.

Do you know where "console=ttyS1, 115200n8" should go? I dug the source code, /boot/cmdline.txt is for Android only.

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Re: How to enable serial console?

#12 Post by Aki »

Hello sereneguy,

I’m happy the situation is improved.

The UART for terminal console should be tty3 (UART 3, I suppose, counting from zero) according to the available documentation. Therefore, you should activate also UART 3 from configuration file config.txt (see my previous message) before trying to connect to it.

The only specification found so far about kernel parameters is here [1], but this require accessing the console boot loader before booting the operating system. Further specifications are here [2]:
Boot Linux:
-----------
The "bootm" command is used to boot an application that is stored in
memory (RAM or Flash). In case of a Linux kernel image, the contents
of the "bootargs" environment variable is passed to the kernel as
parameters. You can check and modify this variable using the
"printenv" and "setenv" commands:


=> printenv bootargs
bootargs=root=/dev/ram

=> setenv bootargs root=/dev/nfs rw nfsroot=10.0.0.2:/LinuxPPC nfsaddrs=10.0.0.99:10.0.0.2

=> printenv bootargs
bootargs=root=/dev/nfs rw nfsroot=10.0.0.2:/LinuxPPC nfsaddrs=10.0.0.99:10.0.0.2

=> bootm 40020000
## Booting Linux kernel at 40020000 ...
Image Name: 2.2.13 for NFS on TQM850L
Image Type: PowerPC Linux Kernel Image (gzip compressed)
Data Size: 381681 Bytes = 372 kB = 0 MB
Load Address: 00000000
Entry Point: 0000000c
Verifying Checksum ... OK
Uncompressing Kernel Image ... OK
Linux version 2.2.13 (wd@denx.local.net) (gcc version 2.95.2 19991024 (release)) #1 Wed Jul 19 02:35:17 MEST 2000
Boot arguments: root=/dev/nfs rw nfsroot=10.0.0.2:/LinuxPPC nfsaddrs=10.0.0.99:10.0.0.2
time_init: decrementer frequency = 187500000/60
Calibrating delay loop... 49.77 BogoMIPS
Memory: 15208k available (700k kernel code, 444k data, 32k init) [c0000000,c1000000]
...

If you want to boot a Linux kernel with initial RAM disk, you pass
the memory addresses of both the kernel and the initrd image
More info about "The U-Boot Documentation" is here [3].

Have you checked if the serial ports are detected by Linux after booting on the SBC at the software/hardware level ?

[1] https://wiki.debian.org/U-boot/
[2] https://github.com/TinkerBoard/debian_u-boot
[3] https://u-boot.readthedocs.io/en/latest/
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Re: How to enable serial console?

#13 Post by sereneguy »

Hi,

The board I have, the 2S, doesn't have uart3. The document you referred in the previous post was for different board, Edge R.
Please see attached.
Attachments
Tinker2S.png
Tinker2S.png (309.34 KiB) Viewed 8598 times

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Re: How to enable serial console?

#14 Post by Aki »

sereneguy wrote: 2021-08-24 22:31 Hi, The board I have, the 2S, doesn't have uart3. The document you referred in the previous post was for different board, Edge R.
Please see attached.
Hello Sereneguy,

I'm sorry that I misunderstood the UART number you are interested in.

I try to recap the documentation supplied by the manufacturer for your board with Debian OS from [0]:
- Quick Start Guide [1]
- User Manual [2]
- Drawing and Schematics [3]
- Qualified vendor list [4]
- Download Software [5]
- Source Code for uboot and Linux Kernel [6[[8][9].

Some questions.

What are the contents of your config.txt ?

Have you modified the file config.txt in the userdata partiotion in the SD to activate UART4 as shown in [7] (even if for the different Model Tinker_Edge_R) ? The current switchable functions are listed below and I suppose should defined as shown below:

Code: Select all

##### Hardware Interface Config #####  
## Note: uart4 and spi1 are the same pins. Set the latter one while both on. 
## 
## Note: fiq_debugger and uart0 use the same pin. Set fiq_debugger first while both on. 
#
intf:fiq_debugger=on 
intf:uart0=on
intf:uart4=on
#  intf:i2c6=off 
#  intf:i2c7=off 
#  intf:i2s0=off 
#  intf:spi1=off
#  intf:spi5=off
#  intf:pwm0=off
#  intf:pwm1=off 
#  intf:pwm3a=off
(note the activation of fiq_debugger, uart0 and uart4)

Then, as you can see in the user manual [2], there is also a "Debug UART header" for which is reported:
This Debug UART header provides a separate UART port, allowing developers to use and develop with the
serial console without occupying the 40-pin GPIO’s UART ports.
Therefore, have you tried to connect to this header ?

Thus, have you tried to verify which are the UARTS detected by Debian after booting ? You can check it, for example, with some commands as user root typed from the Tinker Board console, for example:

Code: Select all

script log.txt
apt install setserial
dmesg | grep tty
systemctl | grep tty
setserial -gv
exit
The output of the previous commands will be recorded in the file log.txt that you could send or analyse by yourself.

The setup/configuration of console should also be done after kernel loading (from Debian) using, for example, the setserial command.

[0] https://tinker-board.asus.com/documentation.html
[1] https://tinker-board.asus.com/doc_tb2.html#qsg
[2] https://tinker-board.asus.com/doc_tb2.html#user
[3] https://tinker-board.asus.com/doc_tb2.html#schematics
[4] https://tinker-board.asus.com/doc_tb2.html#qvl
[5] https://tinker-board.asus.com/download- ... r-board-2s
[6] https://github.com/TinkerBoard2
[7] https://tinker-board.asus.com/images/do ... tarted.pdf
[8] https://github.com/TinkerBoard/debian_u-boot
[9] https://github.com/TinkerBoard/debian_kernel
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Re: How to enable serial console?

#15 Post by sereneguy »

Hello Aki,

This is what I modified on my config.txt:

Code: Select all

intf:fiq_debugger=off
intf:uart0=on
I disabled fiq_debugger simply because on different model (I think Edge R), it says that uart0 is shared with fiq_debugger.

Yes, I have been using that GPIO header.
Debug UART works, and uart0 works (but I initialized it with Periphery).
The setup/configuration of console should also be done after kernel loading (from Debian) using, for example, the setserial command.
uart0 has been working, the only problem I have right now is that I don't have console on uart0.

My bottom line question is, where the "setup/configuration of console after kernel loading" took place? Which file I should modify to setup console after kernel loading?

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Re: How to enable serial console?

#16 Post by Aki »

sereneguy wrote: 2021-08-21 03:03 Yes, I already modified config.txt as I mentioned in my first post.
I just added "console=ttyS1,115200n8" to cmdline.txt too, still not working.
Btw, the cmdline.txt was empty, it has that line I added.
Did I miss something?
Hi sereneguy,

I suppose there is a misunderstanding. You are talking about /boot/config.txt in the partition named rootfs on the memory card, while I was taking about cmdline.txt in the partition named userdata on the same memory card (where the operationg system is stored). As shown in one of my previous message, the disk image contains several partitions:

Code: Select all

$ mmls Tinker_Board_2-Debian-Buster-v2.0.0-20210413.img 
GUID Partition Table (EFI)
Offset Sector: 0
Units are in 512-byte sectors

      Slot      Start        End          Length       Description
000:  Meta      0000000000   0000000000   0000000001   Safety Table
001:  -------   0000000000   0000016383   0000016384   Unallocated
002:  Meta      0000000001   0000000001   0000000001   GPT Header
003:  Meta      0000000002   0000000033   0000000032   Partition Table
004:  000       0000016384   0000024575   0000008192   uboot
005:  001       0000024576   0000032767   0000008192   trust
006:  002       0000032768   0000040959   0000008192   misc
007:  003       0000040960   0000106495   0000065536   boot
008:  004       0000106496   0000172031   0000065536   recovery
009:  005       0000172032   0000237567   0000065536   backup
010:  006       0000237568   0000368639   0000131072   userdata <=====
011:  007       0000368640   0008056567   0007687928   rootfs
The file that is probably suited for configuration of kernel parameters is cmdline.txt in userdata partition, whose contents are (mounting the image from a computer different from the SBC):

Code: Select all

root@debian:# mkdir mnt
root@debian:# mount -t ext2 -o loop,offset=121634816 Tinker_Board_2-Debian-Buster-v2.0.0-20210413.img mnt/
root@debian:# cd mnt/
root@debian:# ls -l
total 286
-rwxrwxr-x 1 root root  87402  8 mar 03.28 200frames_count.h264
-rwxrwxr-x 1 root root  81582  8 mar 03.28 belle-nuit-testchart-1080p.png
-rw-rw-r-- 1 root root     58  8 mar 03.28 cmdline.txt  <=====
-rw-rw-r-- 1 root root   1550  8 mar 03.28 config.txt
drwx------ 2 root root  12288 13 apr 06.09 lost+found
drwxrwxr-x 2 root root   2048 13 apr 06.09 overlays
-rwxrwxr-x 1 root root 101760  8 mar 03.28 piano2-CoolEdit.mp3
Your board should be able to be configured to start as a USB device to inspect and configure the cmdline.txt in userdata partition for the console data parameter. Also the config.txt file should be the one in the userdata partition.
sereneguy wrote: 2021-08-29 01:40 Hello Aki,
[..] My bottom line question is, where the "setup/configuration of console after kernel loading" took place? Which file I should modify to setup console after kernel loading?
The serial device must be activated at hardware and firmware level before booting the kernel (probably by uboot). Then, the serial device is detected and eventually configured at kernel level (at boot using the console parameter or after boot at user level with specific commands, as showed in a my previous message). After serial device configuration, the console is configured at operating system (OS) level by system services. Your Debian installation uses systemd, so you can see here [1]. Therefore the serial device must recognized by OS before the serial console configuration by the OS itself.

Have you analyzed Debian system logs as suggested in my previous message ? Is the serial device corresponding to UART4 is detected by kernel ?

Have you available a Debian/Linux installation on you “primary” (desktop/notebook) computer ?

HTH

[1] http://0pointer.de/blog/projects/serial-console.html
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Aki
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Re: How to enable serial console?

#17 Post by Aki »

Hello sereneguy,
Are there any updates?
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sereneguy
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Re: How to enable serial console?

#18 Post by sereneguy »

Aki wrote: 2021-09-06 09:12 Hello sereneguy,
Are there any updates?
Hi Aki,

Thank you for your answers and for checking on me. I have been focusing on other distros for this board as I needed to enable a feature in the kernel and it lacked of documentation in rebuilding the kernel.

Actually both of the config.txt and cmdline.txt that I was talking about are in the same directory (/boot).
But anyway, I don't need the console anymore as I switched the approach to achieve what I need.

A side note, I got the answer from Tinkerboard engineer. in how to enable UART at startup.
It's by adding it to the "overlay" in config.txt

I need to replace

Code: Select all

overlay=
to

Code: Select all

overlay=console-uart0-overlay

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