Editing N900 Hardware Power Consumption

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This page contains information on the amount of energy used by each subsystem of the [[Nokia N900|N900]], and where applicable ways it can be reduced.
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you can do it yourself, but you must be tech savvy. Or you can send it away to Amazon for about the cost of [...]+shipping chgeras and they'll replace it for you. *You can expand your memory on the Nook and on the Sony touch. The Kindle you cannot, though the Kindle will hold 3,500 books, don't know if you need more space then that?! *Nook has a fancy color touch screen at the bottom. While the Sony touch has a touch screen(the entire screen), it was slow to respond, very klunky and not very pretty. The kindle is loaded with buttons along the outside of the screen. * all three have a built in dictionary, which I think is just awesome. *The new kindle now meets with the nook on their slim width. People used to say the nook was more comfortable to hold because of the width, now the kindle will be as well. *Yet, the Nook is heavier by about 3 oz then the Kindle or Sony. *The Nook battery life lasts about 10 days with wifi off, the Sony has 14 days, and the new kindle is up to a month with wifi off(3 weeks with it on)This wasn't a big deal to me, and I was more interested in the other features the Nook DID have, like replaceable battery and expandable memory. *And you may be wondering, why did I purchase a Sony Touch, and then scamper back hours later to return it? Well. When I got it out of the box, it wasn't techy enough for me. It felt like a very basic, bare bones E-reader. And I already had in my head all the things you hear about the nook: books more expensive, and for some reason I thought it wasn't epub friendly. But the moment I had that Sony in my hand, I went to look at the nook more indepth online. The Sony online library was nothing in comparison to Kindle's Amazon.com or Nook's Barnes & Noble. One of my favorite reads recently was The Hunger Games by Suzanne Collins. It was nowhere to be found on Sony. That gave me a bad taste in my mouth. *In the past people have complained that Barnes & Noble is significantly more expensive then Amazon. I did some price comparisons of big titles, and found them most of the time to be exactly the same. I think Barnes & Noble might be trying to keep in line with Amazon to draw more readers(Like ME!) into getting the Nook. On the whole, the nook is everything I wanted. I've downloaded some free classics from google books, I've taken out library ebooks Help other customers find the most helpful reviewsa0Was this review helpful to you?a0  | a0
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Much of any reduction will require additional software, some may be possible by altering user behavior in ways that do not impact the users overall experience..
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Measuring power usage is hard. For example, power consumption of the speakers/speaker-amp has to be disentangled from power consumption of reading a file from SD/eMMC, decoding it, PulseAudio's power use, and the DAC power use.
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Below currents are from l3/l4 manual - assumed to be from a supply at 5 V.
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* FMTX 19 mA - l3/4
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* WLAN on - no powersave - 200 mA
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* WLAN transmit 802.11b - 150 mA
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Battery parameters can be monitored thru fuel gauge chip TI BQ27200 [http://focus.ti.com/lit/ds/symlink/bq27200.pdf]
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==Some preliminary numbers using [[N900 Hardware Charge Meter|the battery monitor chip]].==
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These numbers are biased, and represent best cases. Some have had outliers which may be normal and unavoidable current spikes removed. This is under the assumption that the minimal power represents the minimum power achievable, and it should long-term be possible to - possibly with software patches - achieve these. +x indicates the measurement is for that element only. A raw measurement has no + (marked "T"), and is a total consumption of whole device, when operated in that state. Unless otherwise mentioned, numbers are for the idle locked case, with screen off, battery voltage "full" = 4.0 to 4.1V.
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Assume
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* Suspend (echo mem >/sys/power/state), wifi and GSM off. 2 mA T *)
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* Suspend, GSM on, connected to 3G (2 bars) 5 mA T *)
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* Suspend, GSM on, connected to 2G. (2 bars) 3.6 mA T *) 
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    *): states not recommended, used for test purposes only
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* Idle, no SIM, wlan off 7 mA@4.1 V T
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* Wifi on with maximum powersaving. +~2 mA
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* BT enabled, no headset connected +2 mA with ~1/5 time spikes to +9 mA
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* MMC card in. Under +1 mA
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* Xchat running, sporadic traffic. +8 mA
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* Screen on, no backlight. +80 mA
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* Backlight on max +150 mA, +40mA on 4 of 5 steps in simple brightness applet & low ambient (/sys/class/backlight/acx565akm/brightness = 63)
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* Media player playing MP3, one step above mute. 110 mA T
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* Vibrator at max +120 mA
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* md5sum /dev/zero 250 mA T
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* md5sum /dev/mmcblk1p1 - 1G SD card. 240 mA T
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* md5sum /dev/mmcblk0 - internal MMC 240 mA T (these indicate the CPU is somewhat idle, waiting on IO, and this counteracts any increased power use by the memory)
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* camera active, showing preview. (backlight off) 210 mA T
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* GPS - location test gui - in continuous GPS recieve mode - +50-80 mA
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* 3G connected, good signal, no data or other activity +8 mA.
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* 2G connected, good signal, no data or other activity +5 mA
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===2G data, short pings===
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(all Total - ATTENTION, these values depend on distance from device to base station and thus how much TX RF power it needs)
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* 1 s ping 130 mA
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* 10 s ping 70 mA
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* 30 s ping 45 mA
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===3.5G data, short pings===
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* 1 s 186 mA
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* 10 s 120 mA approx.
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* 30 s 136 mA
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===3.5g data, long pings (8000 bytes)===
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* 1 s 240 mA
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* 10 s 205 mA
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* 30 s 120 mA
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===2G data, long pings (8000 bytes) (with specified seconds between pings)===
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* 1 s 160 mA
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* 10 s 105 mA
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* 30 s 50 mA
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3G sending file at 150 k/s 375 mA
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3G recieving at 200 k/s 275 mA
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==random adds:==
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===2x bash infinite loops, by frequency===
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* 250MHz 278mW T
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* 500MHz 524mW T
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* 805MHz 903mW T
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* 900MHz 1064mW T
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So it seems like the power saving cpufreq hacks are largely irrelevant and one would always use ondemand for maximum CPU peak throughput. Needs further testing with irregular I/O-dependent load tho.
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'''NOTE: everything >500MHz WILL destroy your CPU long term, due to overheating and EM''' This is as evident as the rule "You shall not operate 12V incandescent Lamp at 15V or 20V"
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--[[User:joerg_rw|joerg_rw]] 12:28, 13 May 2015 (UTC)
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WLAN PS-mode medium,10 mW, ssh login active, local xterm with bq27200 script loop 20, screen blanked, aggressive custom breathing indicator light: 20 mA
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xchat 8 freenode chan, wifi PSM medium, screen locked:
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<pre>
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Nokia-N900-42-11:~# bin/bq27200.sh 20
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LOOPMODE=20
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      mv  RSOC CSOC mA  NAC  CACD CACT TTF  TTE  TEMP EDV1 LOW
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18:36 4092 100  100  -134 1187 1187 1187 65535 530  37  0
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18:36 4092 100  100  -17  1186 1186 1186 65535 3990  37  0
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18:37 4106 99  99  -68  1186 1186 1186 65535 1042  37  0
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18:37 4095 99  99  -52  1185 1185 1185 65535 1359  36  0
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18:37 4130 99  99  -18  1185 1185 1185 65535 3807  36  0
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18:38 4092 99  99  -138 1184 1184 1184 65535 511  36  0
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18:38 4090 99  99  -110 1184 1184 1184 65535 644  36  0
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18:38 4090 99  99  -57  1183 1183 1183 65535 1241  36  0
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18:39 4090 99  99  -118 1183 1183 1183 65535 597  36  0
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18:39 4114 99  99  -34  1182 1182 1182 65535 2077  36  0
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18:39 4127 99  99  -17  1182 1182 1182 65535 3569  36  0
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18:40 4122 99  99  -77  1181 1181 1181 65535 570  36  0
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18:40 4087 99  99  -64  1180 1180 1180 65535 3403  36  0
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</pre>
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7mAh / 4min = 7*60mA_min / 4min = ~105mA(h/h);  obviously depends a lot on IRC activity during test period
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===A script to monitor the power consumption for a minute using bq27x00_battery===
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The shell script using i2cdump affects measurements a lot so it's better to use the kernel module.
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'''CITATION NEEDED! Why should a shell script and i2cget be inferior to a perl script and a deprecated kernel module?  
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--[[User:joerg_rw|joerg_rw]] 12:18, 13 May 2015 (UTC) '''
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Go measure it yourself.
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[[User:l29ah|l29ah]] 23:40, 14 May 2015 (UTC)
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this only would show that the kernel module and/or the perl script are buggy. Actually the chip is better in doing sum than a script, it has registers for that and works completely transparent without any sw attention--[[User:joerg_rw|joerg_rw]] 14:26, 16 October 2017 (UTC)
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<pre>apt-get install perl</pre>
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<pre>
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#!/usr/bin/perl
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use strict;
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use warnings;
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use List::Util qw(sum);
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sub mean { return @_ ? sum(@_) / @_ : 0 }
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my @pa;
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for (my $i = 0; $i < 15; $i++) {
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open(my $cf, '<:encoding(UTF-8)', '/sys/class/power_supply/bq27200-0/current_now');
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open(my $vf, '<:encoding(UTF-8)', '/sys/class/power_supply/bq27200-0/voltage_now');
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my $cc = <$cf>;
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my $vc = <$vf>;
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my $pc = $cc * $vc / 1000000000; # mW
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push @pa, $pc;
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sleep(4);
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}
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print mean(@pa);
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</pre>
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chip-based more exact and smarter way:
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--[[User:joerg_rw|joerg_rw]] 15:02, 16 October 2017 (UTC)
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<pre>
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IroN900:~# bq27k-detail2|grep -A1 0x23; sleep 60; bq27k-detail2|grep -A1 0x23
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0x23 - 0x22:  3031  SAE Available Energy High - Low Byte            29.2  µV2h (2)  R
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                    *29.2 / 20 =  4425 mWh
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0x23 - 0x22:  3029  SAE Available Energy High - Low Byte            29.2  µV2h (2)  R
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                    *29.2 / 20 =  4422 mWh
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</pre>
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(4425 mWh -  4422 mWh) / 1/60h = 180mW
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<pre>
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IroN900:~# bq27k-detail2|grep -A1 0x23; sleep 180; bq27k-detail2|grep -A1 0x23
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0x23 - 0x22:  3022  SAE Available Energy High - Low Byte            29.2  µV2h (2)  R
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                    *29.2 / 20 =  4412 mWh
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0x23 - 0x22:  3019  SAE Available Energy High - Low Byte            29.2  µV2h (2)  R
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                    *29.2 / 20 =  4407 mWh
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</pre>
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(4412 mWh - 4407 mWh ) * 3600 s/h / 180 s = 100mW
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most accurate method: get average of NAC over a long period:
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<pre>IroN900:~# bq27200.sh 300
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LOOPMODE=300 RS=22
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      mv  RSOC CSOC mA  NAC  CACD CACT TTF  TTE  TEMP
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17:50 4115 96  96  -41  1098 1098 1098 65535 1606  25  NOACT:0 IMIN:0 CI:0 CALIP:0 VDQ:1 EDV1:0 EDVF:0
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17:55 4131 96  96  -13  1095 1095 1095 65535 4882  25  NOACT:0 IMIN:0 CI:0 CALIP:0 VDQ:1 EDV1:0 EDVF:0
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18:00 4131 96  96  -14  1094 1094 1094 65535 4496  24  NOACT:0 IMIN:0 CI:0 CALIP:0 VDQ:1 EDV1:0 EDVF:0
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18:05 4131 96  96  -22  1091 1091 1091 65535 2884  24  NOACT:0 IMIN:0 CI:0 CALIP:0 VDQ:1 EDV1:0 EDVF:0
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18:10 4123 95  95  -109 1087 1087 1087 65535 594  25  NOACT:0 IMIN:0 CI:0 CALIP:0 VDQ:1 EDV1:0 EDVF:0
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18:15 4118 95  95  -41  1084 1084 1084 65535 1572  25  NOACT:0 IMIN:0 CI:0 CALIP:0 VDQ:1 EDV1:0 EDVF:0
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18:20 4118 95  95  -23  1080 1080 1080 65535 1884  25  NOACT:0 IMIN:0 CI:0 CALIP:0 VDQ:1 EDV1:0 EDVF:0
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18:25 4110 94  94  -33  1077 1077 1077 65535 1906  24  NOACT:0 IMIN:0 CI:0 CALIP:0 VDQ:1 EDV1:0 EDVF:0
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18:30 4118 94  94  -34  1076 1076 1076 65535 1859  24  NOACT:0 IMIN:0 CI:0 CALIP:0 VDQ:1 EDV1:0 EDVF:0
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18:35 4107 94  94  -12  1073 1073 1073 65535 5156  24  NOACT:0 IMIN:0 CI:0 CALIP:0 VDQ:1 EDV1:0 EDVF:0
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18:40 4113 94  94  -143 1069 1069 1069 65535 447  25  NOACT:0 IMIN:0 CI:0 CALIP:0 VDQ:1 EDV1:0 EDVF:0
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</pre>
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average delta-NAC per 5 minutes: 3mAh = 36mAh/h
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delta-NAC 17:50 4115 96 1098  -  18:20 4118 95 1080 = 18mAh/30min = 36mA
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The noise observed in spot reading of "mA" and "TTE" values is from random system activity. It averages out just fine to match the 36mA from long term measure.
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Above test been done on a locked/dimmed device on WLAN with working PSM, xchat active
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==Software==
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Many software subsystems interact to aim to reduce battery usage.
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* [[Wifi power saving mode]]
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* http://hssl.cs.jhu.edu/~neal/woodchuck/blog/2011/09/22/Wireless_Transfers_are_Battery_Intensive/
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[[Category:N900]]
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[[Category:N900 Hardware]]
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