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I'm trying to measure instaneous power comsumption by processor on ARM-Cortex-A9/Ubuntu 12.04 platform.

Does anyone know how to do this?

enc
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    are you looking for some special trick, or standard methods like a shut resistor and something to monitor the voltage across that? Like a scope if you are interested in instantaneous consumption. The processor isnt going to tell you anything all that interesting, and as mentioned you are the mercy of the of the chip vendor not ARM, so if the chip vendor docs dont have anything (I doubt seriously that they would have something) they you have to measure the power rails or incoming power, basic stuff. Maybe try electronics.stackexchange instead of stack overflow. – old_timer Aug 03 '12 at 16:55

2 Answers2

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There are 4 obvious approaches to this:

  • Estimate it from other measurable parameters (e.g. CPU load)
  • Measuring current sense resistors in the on-board power supplies
  • Measuring entire-system power draw using an external supply with some kind of data-logging [a low value resistor and a voltmeter can also be used]
  • [If measuring power draw by a certain application] run the code on some other device that does have this functionality. [Apple's dev-tools and iOS provide incredible levels of support for this. Also fantastic for profiling too].

Since you're using the OMAP4460 (Pandaboard per chance?) it'll probably be paired with the TWL6030 power supply IC. A quick look at the datasheet suggests that it's capable of measuring current draw when running from battery (this is how the battery level indicator is implemented). There will be driver support for this. The OMAP4430 (and probably by extension 4460) doesn't have power supply monitoring of its own.

Might also be worth looking on TI's website for white-papers. This is a common enough thing to do.

marko
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I think it mainly depends on your processor or SOC manufacturer. ARM defines processor core, manufacturer defines everything around it (like peripherials etc.).

Also when Ubuntu is ported on your platform, maybe there just be some power measuring application which also supports that platform.

René Kolařík
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  • I'm using TI OMAP4460. However, is there any general way to measure power of ARM processor like C API? – enc Aug 03 '12 at 07:08
  • I would recommend you this: http://omappedia.org (http://omappedia.org/wiki/LinuxOmapKernelGitTrees). If you want C api, there has to be linux kernel driver which communicates with HW and gives you this api. – René Kolařík Aug 03 '12 at 07:23