Re: [gentoo-user] wakeup from suspend

waltdnes@××××××××.org <waltdnes@××××××××.org> [16-01-11 04:04]:
> On Sun, Jan 10, 2016 at 02:55:57PM +0100, Meino.Cramer@×××.de wrote
> > Hi,
> >
> > currently I am experimenting with a new embedded system
> > (OrangePI PC). I want to suspend the system to RAM.
> > After a period of time the system should wakeup.
> >
> > The RTC on the board seems to support alarms.
> >
> > Is there a tool to set the alarm time of an RTC
> > from the commandline like hwclock set the RTC
> > time itsself?
> >
> > I couldn't find one (or successfully overlooked it...)
> >
> > Thank you very much in advance for any help!
> > Best regards,
> > Meino
>
>   I'm not aware of any utilities.  Is it linux, and how good are you at
> shell scripts?  Two virtual files you'll need to know about are...
>
>   /sys/class/rtc/rtc0/since_epoch
>   /sys/class/rtc/rtc0/wakealarm
>
>   Note that writing to /sys requires root privileges.  Both files are in
> seconds since 1970-01-01 00:00:00 UTC.  This is the same output that
> "date +%s" produces.  To test it, run the command...
>
> date +%s ; cat /sys/class/rtc/rtc0/since_epoch
>
>   Let's say that you want it wake up in 3 minutes (i.e. 180 seconds from
> now).  You'll have to use either "eval" or backticks.  The command
> would be...
>
> #!/bin/bash
> echo $(( 180 + `cat /sys/class/rtc/rtc0/since_epoch` )) > /sys/class/rtc/rtc0/wakealarm
>
> ...and powerdown.  It should wake up 3 minutes after you issued the
> command.
>
>   How about specifying a future time, you ask?  First, we need to know
> the input format.  The "--date" command uses the format
> "MM/DD/YYYY HH:mm:ss" (Month/Day/Year Hour:Minute:Second)
> the brackets indicate optional items.  To get the seconds since epoch at...
>
> year 2016
> month 01
> day 20
> hour 23
> minute 00
> second 00
>
> the command is...
>
>   date +%s --date="01/20/2016 23:00:00"
>
> ...which outputs 1453348800
>
> To set a wakeup alarm for that time...
>
> date +%s --date="01/20/2016 23:00:00" > /sys/class/rtc/rtc0/wakealarm
>
>   You'll probably want to write a script to accept input from a user or
> another program.  Beware of UTC offsets and Daylight Saving Time.
>
> --
> Walter Dnes <waltdnes@××××××××.org>
> I don't run "desktop environments"; I run useful applications
>

Hi Walter,

THANKS :) for explanation...I am quite familiar with shell scripting
under Unices... :)

Your mail will help me a lot!

Best regards,
Meino