On 2018-06-20, bob prohaska  wrote:
> Does the Pi (Pi3, in particular) have any ability to report
> interal power supply voltages? Spot checks with a voltmeter
> on the GPIO header are some help, but a running test that can
> be logged over time would be much more informative.
>
> I found a web page suggesting "vcgencmd measure_volts core"
> but on my Pi3 it reports VCHI "initialization failed". Apropos
> didn't hit on voltage or volt
>
> As it happens I want to do this under FreeBSD, but if it can't
> be done under Raspbian there's no hope. If it can, then I'll
> look further.
>

I got initialization failed  until I ran it as root (or used sudo)

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