A20 Micro keyboard not working through serial connector

Hi,

I yesterday built a new image for my A20-OLinuXino-MICRO board (Armbian 5.17 Jessie with kernel 4.7.3)

At first boot, everything worked fine. I could manage to connect through SSH and changed root password and add new user.

However, avec adding a Hard Disk (on the SATA connector) and reboot, I could not manage to connect via SSH

So I tried the serial (UART) connector. After some tries and a non responding console (I could see no kernel messages at boot to I had to change the verbosity), I finally succeeded in booting with a console prompt on serial connector.

But...

The keyboard is not responding on that serial connector.

After a few tries, I discovered that the problem occurred to be in u-boot too (U-Boot 2016.07-armbian) : before autoboot, typing any key does nothing

Hit any key to stop autoboot:  0

I tried with several serial cable (which work fine on other board's connector)

I removed the hard disk from SATA connector: same result

Below the beginning of my boot.cmd

setenv verbosity 7
setenv bootargs "console=ttyS0,115200 root=/dev/mmcblk0p1 rootwait nomodeset rootfstype=ext4 cgroup_enable=memory swapaccount=1 sunxi_ve_mem_reserve=0 sunxi_g2d_mem_reserve=0 sunxi_no_mali_mem_reserve sun
#the ending of the file is the same as default boot.cmd

So I am a little bit out of idea of what is happening there.

Is there anything special to activate UART console on A20-OLinuXino-MICRO in u-boot / kernel ?