| page.title=Measuring Power Values |
| @jd:body |
| |
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| <div id="qv-wrapper"> |
| <div id="qv"> |
| <h2>In this document</h2> |
| <ol id="auto-toc"></ol> |
| </div> |
| </div> |
| |
| |
| <p>Device manufacturers must provide a component power profile in |
| <code>/frameworks/base/core/res/res/xml/power_profile.xml</code>.</p> |
| |
| <p>To determine values for power profiles, use hardware that measures the power |
| being used by the device and perform the various operations for which |
| information is needed. Measure the power use during those operations and compute |
| the values (deriving differences from other baseline power uses as appropriate). |
| </p> |
| |
| <h2 id="values">Power values</h2> |
| |
| <table> |
| <tr> |
| <th>Name</th> |
| <th>Description</th> |
| <th>Example Value</th> |
| <th>Notes</th> |
| </tr> |
| <tr> |
| <td>none</td> |
| <td>Nothing</td> |
| <td>0</td> |
| <td></td> |
| </tr> |
| |
| <tr> |
| <td>screen.on</td> |
| <td>Additional power used when screen is turned on at minimum brightness.</td> |
| <td>200mA</td> |
| <td>Includes touch controller and display backlight. At 0 brightness, not the |
| Android minimum which tends to be 10 or 20%.</td> |
| </tr> |
| |
| <tr> |
| <td>screen.full</td> |
| <td>Additional power used when screen is at maximum brightness, compared to |
| screen at minimum brightness.</td> |
| <td>100mA-300mA</td> |
| <td>A fraction of this value (based on screen brightness) is added to the |
| screen.on value to compute the power usage of the screen.</td> |
| </tr> |
| |
| <tr> |
| <td>bluetooth.active</td> |
| <td>Additional power used when playing audio through Bluetooth A2DP.</td> |
| <td>14mA</td> |
| <td></td> |
| </tr> |
| |
| <tr> |
| <td>bluetooth.on</td> |
| <td>Additional power used when Bluetooth is turned on but idle.</td> |
| <td>1.4mA</td> |
| <td></td> |
| </tr> |
| |
| <tr> |
| <td>wifi.on</td> |
| <td>Additional power used when Wi-Fi is turned on but not receiving, |
| transmitting, or scanning.</td> |
| <td>2mA</td> |
| <td></td> |
| </tr> |
| |
| <tr> |
| <td>wifi.active</td> |
| <td>Additional power used when transmitting or receiving over Wi-Fi.</td> |
| <td>31mA</td> |
| <td></td> |
| </tr> |
| |
| <tr> |
| <td>wifi.scan</td> |
| <td>Additional power used when Wi-Fi is scanning for access points.</td> |
| <td>100mA</td> |
| <td></td> |
| </tr> |
| |
| <tr> |
| <td>dsp.audio</td> |
| <td>Additional power used when audio decoding/encoding via DSP.</td> |
| <td>14.1mA</td> |
| <td>Reserved for future use.</td> |
| </tr> |
| |
| |
| <tr> |
| <td>dsp.video</td> |
| <td>Additional power used when video decoding via DSP.</td> |
| <td>54mA</td> |
| <td>Reserved for future use.</td> |
| </tr> |
| |
| <tr> |
| <td>camera.avg</td> |
| <td>Average power use by the camera subsystem for a typical camera |
| application.</td> |
| <td>600mA</td> |
| <td>Intended as a rough estimate for an application running a preview |
| and capturing approximately 10 full-resolution pictures per minute.</td> |
| </tr> |
| |
| <tr> |
| <td>camera.flashlight</td> |
| <td>Average power used by the camera flash module when on.</td> |
| <td>200mA</td> |
| <td></td> |
| </tr> |
| |
| |
| <tr> |
| <td>gps.on</td> |
| <td>Additional power used when GPS is acquiring a signal.</td> |
| <td>50mA</td> |
| <td></td> |
| </tr> |
| |
| <tr> |
| <td>radio.active</td> |
| <td>Additional power used when cellular radio is transmitting/receiving.</td> |
| <td>100mA-300mA</td> |
| <td></td> |
| </tr> |
| |
| <tr> |
| <td>radio.scanning</td> |
| <td>Additional power used when cellular radio is paging the tower.</td> |
| <td>1.2mA</td> |
| <td></td> |
| </tr> |
| |
| <tr> |
| <td>radio.on</td> |
| <td>Additional power used when the cellular radio is on. Multi-value entry, |
| one per signal strength (no signal, weak, moderate, strong).</td> |
| <td>1.2mA</td> |
| <td>Some radios boost power when they search for a cell tower and do not |
| detect a signal. Values can be the same or decrease with increasing signal |
| strength. If you provide only one value, the same value is used for all |
| strengths. If you provide two values, the first is used for no-signal, the |
| second value is used for all other strengths, and so on.</td> |
| </tr> |
| |
| <tr> |
| <td>cpu.speeds</td> |
| <td>Multi-value entry that lists each possible CPU speed in KHz.</td> |
| <td>125000KHz, 250000KHz, 500000KHz, 1000000KHz, 1500000KHz</td> |
| <td>The number and order of entries must correspond to the mA entries in |
| cpu.active.</td> |
| </tr> |
| |
| <tr> |
| <td>cpu.idle</td> |
| <td>Total power drawn by the system when CPUs (and the SoC) are in system |
| suspend state.</td> |
| <td>3mA</td> |
| <td></td> |
| </tr> |
| |
| <tr> |
| <td>cpu.awake</td> |
| <td>Additional power used when CPUs are in scheduling idle state |
| (kernel idle loop); system is not in system suspend state.</td> |
| <td>50mA</td> |
| <td>Your platform might have more than one idle state in use with differing |
| levels of power consumption; choose a representative idle state for longer |
| periods of scheduler idle (several milliseconds). Examine the power graph on |
| your measurement equipment and choose samples where the CPU is at its lowest |
| consumption, discarding higher samples where the CPU exited idle.</td> |
| </tr> |
| |
| <tr> |
| <td>cpu.active</td> |
| <td>Additional power used by CPUs when running at different speeds.</td> |
| <td>100mA, 120mA, 140mA, 160mA, 200mA</td> |
| <td>Set the max speed in the kernel to each of the allowed speeds and peg the |
| CPU at that speed. The number of entries here correspond to the number of |
| entries in cpu.speeds, in the same order.</td> |
| </tr> |
| |
| <tr> |
| <td>battery.capacity</td> |
| <td>Total battery capacity in mAh.</td> |
| <td>3000mAh</td> |
| <td></td> |
| </tr> |
| </table> |
| |
| <h2 id="sample">Sample file</h2> |
| |
| <pre> |
| <!-- Most values are the incremental current used by a feature, in mA (measured at |
| nominal voltage). OEMs must measure and provide actual values before shipping a device. |
| Example real-world values are given, but are dependent on the platform |
| and can vary significantly, so should be measured on the shipping platform with a power meter. |
| --> |
| 0 |
| 200 |
| 160 |
| 10 |
| <!-- Bluetooth stereo audio playback 10.0 mA --> |
| 1.3 |
| 0.5 |
| 30 |
| 100 |
| 12 |
| 50 |
| 50 |
| 75 |
| 1.1 |
| <!-- Strength 0 to BINS-1 (4) --> |
| 1.1 |
| |
| <!-- Different CPU speeds as reported in |
| /sys/devices/system/cpu/cpu0/cpufreq/stats/time_in_state --> |
| |
| 250000 <!-- 250 MHz --> |
| 500000 <!-- 500 MHz --> |
| 750000 <!-- 750 MHz --> |
| 1000000 <!-- 1 GHz --> |
| 1200000 <!-- 1.2 GHz --> |
| |
| <!-- Power consumption when CPU is idle --> |
| 3.0 |
| 50.1 |
| <!-- Power consumption at different speeds --> |
| |
| 100 <!-- 250 MHz --> |
| 120 <!-- 500 MHz --> |
| 140 <!-- 750 MHz --> |
| 155 <!-- 1 GHz --> |
| 175 <!-- 1.2 GHz --> |
| |
| <!-- This is the battery capacity in mAh --> |
| 3000 |
| <!-- Battery capacity is 3000 mAH (at 3.6 Volts) --> |
| |
| </pre> |