Screen sleep mode

Hi !

I would like to force my screen to enter in the framebuffer sleep mode for
saving energy when my board is not used.

I know I have to use the following command lines to force enter in the fb
sleep mode :

    echo 1 > /sys/class/graphics/fb0/blank


And in order to force my screen to get out of the sleep mode :

    echo 0 > /sys/class/graphics/fb0/blank

And the following command line has exactly no consequences :
 echo -e '\033[9;1]' > /dev/ttySAC0 

Unfortunately my board doesn’t enter in sleep mode after a delay. I think I
have to code something in my Qt app so that after a certain time
of inactivity the first command is launched thanks to a QProcess. And once
a somebody put his finger in the touchscreen the second command will have
to be lauched too in order to get back to a normal screen mode... But it
looks very dirty ...

Have you experienced something like that ? And do you know a way to solve
this problem without using Qt stuff, only by configuring the system ?

Thanks !

The display only switches into a power saving mode, if the framebuffer
console is using it. If the framebuffer console is not used, you need to
switch off it by yourself (you already found out how).

And why do you expect anything display related happens when you output
something to your serial console (e.g. /dev/ttySAC0)? This sequence will be
sent out at your RS232 connector (an maybe hits your host but never your
local display).

Enable the framebuffer console in the kernel and you will get a system that
behaves as you expect it.

Indeed, you're very right ! /dev/ttySAC0 is not the good device ....
I'll do as you said (modifying the kernel configuration and using the right
tty device).
I keep you in touch

The kernel I am using is configured with the framebuffer console
(CONIFG_FRAMEBUFFER_CONSOLE=y)

I tried several commands :
echo -e '\033[9;1]' > /dev/pts/0 
and
echo -e '\033[9;1]'

But nothing happens after 1min delay

Maybe QWS is blocking the sleep mode ? But that would be very weird because
I can force the sleep mode without any problem when using QT apps of my own

QWS can block the console sleep mode, as it disables the console and
switches to graphics mode when it starts. But not sure.
Simply run your system without any Qt app running, only the plain console
enabled. Does it switch off in this case? Or did you already test it with
your "2012-03-11 23:56:54" report.

No I forgot to test this. 

In console mode the sleep mode is entered after 1min delay as it should
do... I think QWS blocks the sleep mode.

I found these env variables :
http://qt-project.org/doc/qt-4.8/qt-embedded-envvars.html

But nothing matches the problem.

I also found this :
http://linux.die.net/man/3/qwsserver
This is interesting, it permits to use a screensaver. However I would
rather use the sleep mode in order to save more energy when the board is
not used.