Rockbox mail archive
Subject: Re: Use SLEEP instruction for longer (?) runtime
From: Andrew Jamieson (ajamiesn_at_optusnet.com.au)
OK. For this build (in idle state):
No power save mode: 110mA
CPU Sleep: 98mA
CPU Stop: 95mA
CPU Standby: 81mA
So, it seems having a more efficient scheduler to increase the time spent
sleeping does not seem worthwhile, as the best we can get it only 3mA more
than what we have at the moment (Simon's implementation). It should be
noted that changing the states of various port pins during sleep may have an
effect on this current consumption, causing it to deviate from documented
values. However, any further savings would apply equally to the readings of
'sleep' and 'stop' modes.
Clearly, standby would be awesome if we could implement it, saving up to a
whopping 20% on the best we can currently achieve. However, the reality of
the HW is something of an obstacle. I will do some more hunting on my
Player to see if I can find any ways to reduce the sleep current, and look
for hope as to a standby mode. Updated schematics will follow.
> Oops, yes, that one was recorder-only. I looked for something where the
> thread did nothing but wait for a key to be pressed. The screen that asks
> you want to resume after powering on, and the text file viewer, are two
> things that should work on the player too.
> I've uploaded a new build with has a menu choice to disable interrupts and
> sleep, completely stopping the CPU. This should represent the maximum
> possible power saving without using the standby mode. This should be 20 mA
> according to the docs, but I'm getting a bit suspicious seeing 10 mA of
> savings almost no matter what the software does. It would be nice if you
> could compare the power saving with the CPU completely stopped and at the
> "resume?" screen.
> Just for fun, the new build also includes an option to enter standby mode,
> which would be great if it was only possible to wake up from. Does anyone
> know if NMI is connected to anything useful in the player/recorder?
> Unfortunately, the schematics at http://rockbox.haxx.se/schematics/ makes
> sense at all to me, but I'll look at them again when I'm awake...
> Simon ElÚn
Page was last modified "Jan 10 2012" The Rockbox Crew