Serial Console on UART - Dragonbroad


#1

Hi
How do I enable the serial console on Dragonboard.

I am testing with the Debian Build 110 image.

With my cable connected to the Low Speed connector (UART1) - I can see the boot messages scroll by, the login prompt appear (most times) but it then freezes - i.e. the keyboard wont work.
Board is running correctly - as the HDMI screen has the desktop displayed.

Its as if the kernel has moved the console elsewhere ?


#2

Nothing special is needed to enable the serial console. In fact I’m rather surprised you end up with a login prompt, out-of-the-box LS-UART1 is configured to log in automatically.

Normal behavior is for kernel messages (with timestamps) to pop out for 8-10 seconds, followed by the systemd service start messages (and occasional burst of kernel messages) before finally we get the automatic login messages:

...
[  OK  ] Reached target Graphical Interface.
         Starting Update UTMP about System Runlevel Changes...
[  OK  ] Started Update UTMP about System Runlevel Changes.

Debian GNU/Linux 8 linaro-alip ttyMSM0

linaro-alip login: root (automatic login)

Last login: Tue Dec  6 08:20:48 UTC 2016 on ttyMSM0
Linux linaro-alip 4.4.23-linaro-lt-qcom #1 SMP PREEMPT Thu Oct 6 08:25:14 UTC 2016 aarch64

The programs included with the Debian GNU/Linux system are free software;
the exact distribution terms for each program are described in the
individual files in /usr/share/doc/*/copyright.

Debian GNU/Linux comes with ABSOLUTELY NO WARRANTY, to the extent
permitted by applicable law.
root@linaro-alip:~# 

It should definitely be possible to type into that root prompt in your terminal emulator…


#3

Hi @cortinas,

It could be because of Hardware flow turn on. When the Hardware flow turn on, it shows the symptoms like just you described.

This is the link to instruction of turning off Hardware flow including entire UART usage.
http://www.96boards.org/forums/topic/short-into-to-start-your-dragonboard-410c-with-serial-console/