Tag Archives: serial console

Terminals

I was reading about JWZ’s awesome portrait serial terminal and wondering what would a serial terminal look like today if we could implement it using modern technology.

You could get a flat screen display and mount it in portrait mode. Most have VESA attachments, so it’s a matter of finding a nice portrait VESA stand.

To implement the terminal you could fix a Raspberry Pi or similar to the back of the screen. Could it be powered by the same PSU as the screen? Perhaps if the screen had a USB port.

For the keyboard you’d use a nice USB keyboard.

Of course there’s no reason these days to use an actual serial line, nor to limit ourselves to just a text display. Use wifi to link to the host computer. Use software to emulate an old orange DEC terminal, and X11 to display remote graphics.

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Mele A1000G Quad boot messages

For my reference mainly, attached below are the boot messages from the Mele A1000G Quad with the original Android kernel. Unfortunately the UART connector is just a little bit too small to take the CP2102 USB-serial adapter so now I have to find an Audio CD header block of the sort used by CD-ROMs in the 1990s. However I was able to connect the GND and TX which is enough to get the serial output below.

This site has been very useful.

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Setting up a serial console in qemu and libvirt

I always forget how to do this, but in fact it’s quite simple.

First ensure your libvirt XML contains a fragment like this (my guest, installed using virt-install, already had this).


  


  

Second, edit /boot/grub/grub.conf inside the guest, adding the console=ttyS0 element to the kernel command line:

# virt-edit Guestname /boot/grub/grub.conf
...
title Fedora (2.6.38.6-26.rc1.fc15.x86_64)
	root (hd0,0)
	kernel /vmlinuz ro [...] console=ttyS0
...

You don’t need to set the speed. I believe it defaults to 115200 8N1, but I don’t think that qemu serial ports have a “speed” as such, since the hardware is emulated.

Third, start the guest and dump out the running XML:

# virsh start Guestname && virsh dumpxml Guestname
...
    <console type='pty' tty='/dev/pts/8'>

Notice the randomly assigned pty on the host side (/dev/pts/8). Connect to that with Minicom[1], and you should see boot messages and/or a login prompt.

[1] Is there something better than minicom? It’s a horrible program, always has been.
Yes: screen /dev/ttyUSB0 115200

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