Re: Darwin support for lisp/battery.el.

[Ken Raeburn <raeburn@raeburn.org>]

On Jul 4, 2005, at 03:39, Lute Kamstra wrote:
> My patch tries to test whether pmset supports "-g ps" by looking at
> the exit code.  Does "pmset -g ps" return a non-zero exit code on your
> system?

No, it looks like "pmset -g anything" will give a zero exit status; it  
just doesn't print out anything unless you give it one of the supported  
options.  "pmset -g golf-ball" quite happily returns a zero exit  
status.

> Do you know of a way to get battery information on your system?

 From the command line... not yet.  From some poking around through  
Google, it looks like the output of "ioreg -w0 -l | grep Capacity" may  
have some or all of the data you'd want; I'm not sure yet.

I get:

     | | |   "IOBatteryInfo" = ({"Capacity"=4520,"Amperage"=0,"Cycle  
Count"=139,"Current"=4278,"Voltage"=12368,"Flags"=1090519045,"AbsoluteMa 
xCapacity"=5400})
     | |   |   |     "IOBatteryInfo" =  
({"Capacity"=4520,"Amperage"=0,"Cycle  
Count"=139,"Current"=4278,"Voltage"=12368,"Flags"=1090519045,"AbsoluteMa 
xCapacity"=5400})

on AC current and

     | | |   "IOBatteryInfo" = ({"Capacity"=4520,"Amperage"=0,"Cycle  
Count"=139,"Current"=4278,"Voltage"=12368,"Flags"=4,"AbsoluteMaxCapacity 
"=5400})
     | |   |   |     "IOBatteryInfo" =  
({"Capacity"=4520,"Amperage"=0,"Cycle  
Count"=139,"Current"=4278,"Voltage"=12368,"Flags"=4,"AbsoluteMaxCapacity 
"=5400})

on battery.  (The leading vertical bars seem to be part of an ASCII  
graphical diagram of a hierarchy of registry keys and values.  "-w0"  
seems to mean "width 0", i.e., don't truncate the output lines.)

The Flags field is described a little bit at  
http://www.macosxhints.com/comment.php? 
mode=display&sid=20030311220217671&title=Give+your+battery+a+thorough+ch 
eckup&pid=0
as having value 0x004 on battery and 0x005 on AC (the value 1090519045  
above is 0x41000005) and 0x08x or 0x09x values when power gets low.  I  
didn't find any mention of "battery" in the system header files, nor  
any relevant mention of "power".

It also seems, from some of the other comments, that Current/Capacity  
should be the current level of charge in the battery (so I'm at 94%,  
kind of disappointing immediately after unplugging the power, but the  
Mac GUI display agrees with it).

http://www.dssw.co.uk/sleepcentre/threads/ 
ioreg_bat_sh_was_re_10_3_6_what_.html
indicates that "ioreg -p IODeviceTree -n battery -w 0" may be a better  
choice (it only produces 108 lines of output on my system, versus 4238  
for "ioreg -l -w 0"), but the output still has to be filtered for the  
IOBatteryInfo capacity line.

http://www.macosxhints.com/article.php?story=20030311220217671
has an awk script for reformatting the data, and a claim that
 >> The results for "capacity" and "current" are in microamperes per  
hour (mAh).
I always thought "mAh" was milliamp-hours (times hours, not per hour),  
but some math suggests that 10**6 is probably the right scaling factor  
in there somewhere.

I'm running 10.3.9, and at  
http://www.mitt-eget.com/software/macosx/#battery it says that the  
ioreg output format changed in 10.3.8, and again in 10.4, so parsing  
this may be a little annoying.  However, there's also a link to a  
script which can parse the output, and comments describing what the  
author thinks many of the flags are; following its logic shouldn't be  
too hard.  The tough part may be dealing with the amperage when it's  
nonzero -- apparently it's a 64-bit value which can be negative, but is  
displayed as unsigned.  The emacs I've got on my system parses  
"18446744073709549763" and comes up with "-1", when what we want is  
"-1853".

I'll see if I can poke at this a little more, later...

Ken