1page.title=Measuring Power Values 2@jd:body 3 4<!-- 5 Copyright 2015 The Android Open Source Project 6 7 Licensed under the Apache License, Version 2.0 (the "License"); 8 you may not use this file except in compliance with the License. 9 You may obtain a copy of the License at 10 11 http://www.apache.org/licenses/LICENSE-2.0 12 13 Unless required by applicable law or agreed to in writing, software 14 distributed under the License is distributed on an "AS IS" BASIS, 15 WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 16 See the License for the specific language governing permissions and 17 limitations under the License. 18--> 19<div id="qv-wrapper"> 20 <div id="qv"> 21 <h2>In this document</h2> 22 <ol id="auto-toc"></ol> 23 </div> 24</div> 25 26 27<p>Device manufacturers must provide a component power profile in 28<code>/frameworks/base/core/res/res/xml/power_profile.xml</code>.</p> 29 30<p>To determine values for power profiles, use hardware that measures the power 31being used by the device and perform the various operations for which 32information is needed. Measure the power use during those operations and compute 33the values (deriving differences from other baseline power uses as appropriate). 34</p> 35 36<p>As the goal of a power profile is to estimate battery drain appropriately, 37power profile values are given in current (amps). The Android framework 38multiplies the current by the time for which the subsystem was active and 39computes the mAh value, which is then used to estimate the amount of battery 40drained by the application/subsystem.</p> 41 42<p>Devices with Bluetooth, modem, and Wi-Fi controllers running Android 7.0 and 43higher can provide additional power values obtained from chipset data.</p> 44 45 46<h2 id="multiple-cpus">Devices with heterogeneous CPUs</h2> 47 48<p>The power profile for devices with CPU cores of heterogeneous architecture 49must include the following additional fields: 50<ul> 51<li>Number of total CPUs for each cluster.</li> 52<li>CPU speeds supported by each cluster.</li> 53</ul> 54 55<p>To differentiate between active CPUs and supported CPU speeds for each 56cluster, append the cluster number to the name of the array. Example:</p> 57 58<pre> 59<array name="cpu.active.cluster0"> 60<value>200</value> 61<value>300</value> 62<value>400</value> 63</array> 64<array name="cpu.speeds.cluster0"> 65<value>600000</value> 66<value>800000</value> 67<value>1200000</value> 68</array> 69 70<array name="cpu.active.cluster1"> 71<value>400</value> 72<value>500</value> 73<value>600</value> 74</array> 75<array name="cpu.speeds.cluster1"> 76<value>800000</value> 77<value>1200000</value> 78<value>1400000</value> 79</array> 80</pre> 81 82<h2 id="values">Power values</h2> 83<p>The following table describes available power value settings. To view the 84sample file in AOSP, see 85<a href="https://android.googlesource.com/platform/frameworks/base/+/master/core/res/res/xml/power_profile.xml">power_profile.xml</a>.</p> 86 87<table> 88<tr> 89 <th>Name</th> 90 <th>Description</th> 91 <th>Example Value</th> 92 <th>Notes</th> 93</tr> 94<tr> 95 <td>none</td> 96 <td>Nothing</td> 97 <td>0</td> 98 <td></td> 99</tr> 100 101<tr> 102 <td>screen.on</td> 103 <td>Additional power used when screen is turned on at minimum brightness.</td> 104 <td>200mA</td> 105 <td>Includes touch controller and display backlight. At 0 brightness, not the 106 Android minimum which tends to be 10 or 20%.</td> 107</tr> 108 109<tr> 110 <td>screen.full</td> 111 <td>Additional power used when screen is at maximum brightness, compared to 112 screen at minimum brightness.</td> 113 <td>100mA-300mA</td> 114 <td>A fraction of this value (based on screen brightness) is added to the 115 screen.on value to compute the power usage of the screen.</td> 116</tr> 117 118<tr> 119 <td>wifi.on</td> 120 <td>Additional power used when Wi-Fi is turned on but not receiving, 121 transmitting, or scanning.</td> 122 <td>2mA</td> 123 <td></td> 124</tr> 125 126<tr> 127 <td>wifi.active</td> 128 <td>Additional power used when transmitting or receiving over Wi-Fi.</td> 129 <td>31mA</td> 130 <td></td> 131</tr> 132 133<tr> 134 <td>wifi.scan</td> 135 <td>Additional power used when Wi-Fi is scanning for access points.</td> 136 <td>100mA</td> 137 <td></td> 138</tr> 139 140<tr> 141 <td>dsp.audio</td> 142 <td>Additional power used when audio decoding/encoding via DSP.</td> 143 <td>14.1mA</td> 144 <td>Reserved for future use.</td> 145</tr> 146 147 148<tr> 149 <td>dsp.video</td> 150 <td>Additional power used when video decoding via DSP.</td> 151 <td>54mA</td> 152 <td>Reserved for future use.</td> 153</tr> 154 155<tr> 156 <td>camera.avg</td> 157 <td>Average power use by the camera subsystem for a typical camera 158 application.</td> 159 <td>600mA</td> 160 <td>Intended as a rough estimate for an application running a preview 161 and capturing approximately 10 full-resolution pictures per minute.</td> 162</tr> 163 164<tr> 165 <td>camera.flashlight</td> 166 <td>Average power used by the camera flash module when on.</td> 167 <td>200mA</td> 168 <td></td> 169</tr> 170 171 172<tr> 173 <td>gps.on</td> 174 <td>Additional power used when GPS is acquiring a signal.</td> 175 <td>50mA</td> 176 <td></td> 177</tr> 178 179<tr> 180 <td>radio.active</td> 181 <td>Additional power used when cellular radio is transmitting/receiving.</td> 182 <td>100mA-300mA</td> 183 <td></td> 184</tr> 185 186<tr> 187 <td>radio.scanning</td> 188 <td>Additional power used when cellular radio is paging the tower.</td> 189 <td>1.2mA</td> 190 <td></td> 191</tr> 192 193<tr> 194 <td>radio.on</td> 195 <td>Additional power used when the cellular radio is on. Multi-value entry, 196 one per signal strength (no signal, weak, moderate, strong).</td> 197 <td>1.2mA</td> 198 <td>Some radios boost power when they search for a cell tower and do not 199 detect a signal. Values can be the same or decrease with increasing signal 200 strength. If you provide only one value, the same value is used for all 201 strengths. If you provide two values, the first is used for no-signal, the 202 second value is used for all other strengths, and so on.</td> 203</tr> 204 205<tr> 206 <td>bluetooth.controller.idle</td> 207 <td>Average current draw (mA) of the Bluetooth controller when idle.</td> 208 <td> - </td> 209 <td rowspan=4>These values are not estimated, but taken from the data sheet of 210 the controller. If there are multiple receive or transmit states, the average 211 of those states is taken. In addition, the system now collects data for 212 <a href="#le-bt-scans">Low Energy (LE) and Bluetooth scans</a>.<br><br>Android 213 N and later no longer use the Bluetooth power values for bluetooth.active 214 (used when playing audio via Bluetooth A2DP) and bluetooth.on (used when 215 Bluetooth is on but idle).</td> 216</tr> 217 218<tr> 219 <td>bluetooth.controller.rx</td> 220 <td>Average current draw (mA) of the Bluetooth controller when receiving.</td> 221 <td> - </td> 222</tr> 223 224<tr> 225 <td>bluetooth.controller.tx</td> 226 <td>Average current draw (mA) of the Bluetooth controller when transmitting.</td> 227 <td> - </td> 228</tr> 229 230<tr> 231 <td>bluetooth.controller.voltage</td> 232 <td>Average operating voltage (mV) of the Bluetooth controller.</td> 233 <td> - </td> 234</tr> 235 236<tr> 237 <td>modem.controller.idle</td> 238 <td>Average current draw (mA) of the modem controller when idle.</td> 239 <td> - </td> 240 <td rowspan=4>These values are not estimated, but taken from the data sheet of 241 the controller. If there are multiple receive or transmit states, the average 242 of those states is taken.</td> 243</tr> 244 245<tr> 246 <td>modem.controller.rx</td> 247 <td>Average current draw (mA) of the modem controller when receiving.</td> 248 <td> - </td> 249</tr> 250 251<tr> 252 <td>modem.controller.tx</td> 253 <td>Average current draw (mA) of the modem controller when transmitting.</td> 254 <td> - </td> 255</tr> 256 257<tr> 258 <td>modem.controller.voltage</td> 259 <td>Average operating voltage (mV) of the modem controller.</td> 260 <td> - </td> 261</tr> 262 263<tr> 264 <td>wifi.controller.idle</td> 265 <td>Average current draw (mA) of the Wi-Fi controller when idle.</td> 266 <td> - </td> 267 <td rowspan=4>These values are not estimated, but taken from the data sheet of 268 the controller. If there are multiple receive or transmit states, the average 269 of those states is taken.</td> 270</tr> 271 272<tr> 273 <td>wifi.controller.rx</td> 274 <td>Average current draw (mA) of the Wi-Fi controller when receiving.</td> 275 <td> - </td> 276</tr> 277 278<tr> 279 <td>wifi.controller.tx</td> 280 <td>Average current draw (mA) of the Wi-Fi controller when transmitting.</td> 281 <td> - </td> 282</tr> 283 284<tr> 285 <td>wifi.controller.voltage</td> 286 <td>Average operating voltage (mV) of the Wi-Fi controller.</td> 287 <td> - </td> 288</tr> 289 290<tr> 291 <td>cpu.speeds</td> 292 <td>Multi-value entry that lists each possible CPU speed in KHz.</td> 293 <td>125000KHz, 250000KHz, 500000KHz, 1000000KHz, 1500000KHz</td> 294 <td>The number and order of entries must correspond to the mA entries in 295 cpu.active.</td> 296</tr> 297 298<tr> 299 <td>cpu.idle</td> 300 <td>Total power drawn by the system when CPUs (and the SoC) are in system 301 suspend state.</td> 302 <td>3mA</td> 303 <td></td> 304</tr> 305 306<tr> 307 <td>cpu.awake</td> 308 <td>Additional power used when CPUs are in scheduling idle state 309 (kernel idle loop); system is not in system suspend state.</td> 310 <td>50mA</td> 311 <td>Your platform might have more than one idle state in use with differing 312 levels of power consumption; choose a representative idle state for longer 313 periods of scheduler idle (several milliseconds). Examine the power graph on 314 your measurement equipment and choose samples where the CPU is at its lowest 315 consumption, discarding higher samples where the CPU exited idle.</td> 316</tr> 317 318<tr> 319 <td>cpu.active</td> 320 <td>Additional power used by CPUs when running at different speeds.</td> 321 <td>100mA, 120mA, 140mA, 160mA, 200mA</td> 322 <td>Value represents the power used by the CPU rails when running at different 323 speeds. Set the max speed in the kernel to each of the allowed speeds and peg 324 the CPU at that speed. The number and order of entries correspond to the 325 number and order of entries in cpu.speeds.</td> 326</tr> 327 328<tr> 329 <td>cpu.clusters.cores</td> 330 <td>Number of cores each CPU cluster contains.</td> 331 <td>4, 2</td> 332 <td>Required only for devices with <a href="#multiple-cpus">heterogeneous CPU 333 architectures</a>. Number of entries and order should match the number of 334 cluster entries for the cpu.active and cpu.speeds. The first entry represents 335 the number of CPU cores in cluster0, the second entry represents the number of 336 CPU cores in cluster1, and so on.</td> 337</tr> 338 339<tr> 340 <td>battery.capacity</td> 341 <td>Total battery capacity in mAh.</td> 342 <td>3000mAh</td> 343 <td></td> 344</tr> 345 346</table> 347 348<h2 id="le-bt-scans">Low Energy (LE) and Bluetooth scans</h2> 349<p>For devices running Android 7.0, the system collects data for Low Energy (LE) 350scans and Bluetooth network traffic (such as RFCOMM and L2CAP) and associates 351these activities with the initiating application. Bluetooth scans are associated 352with the application that initiated the scan, but batch scans are not (and 353are instead associated with the Bluetooth application). For an application 354scanning for N milliseconds, the cost of the scan is N milliseconds of rx time 355and N milliseconds of tx time; all leftover controller time is assigned to 356network traffic or the Bluetooth application.</p> 357