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 Date Sat, 21 Apr 2018 15:34:52 +0100 From Jonathan Cameron <> Subject Re: [PATCH v3 1/2] dt-bindings: iio: afe: add current-sense-shunt and voltage-divider
`On Mon, 16 Apr 2018 16:00:44 +0200Peter Rosin <peda@axentia.se> wrote:> On 2018-04-10 17:28, Peter Rosin wrote:> > +Example:> > +The system voltage is circa 12V, but divided down with a 22/200> > +voltage divider to adjust it to the ADC range.> > +> > +SYSV        ADC       GND> > +  +          +         +> > +  |  .-----. | .----.  |> > +  '--| 200 |-+-| 22 |--'> > +     '-----'   '----'> > +> > +sysv {> > +	compatible = "voltage-divider";> > +	io-channels = <&maxadc 1>;> > +> > +	/* Multiply the ADC voltage by 222/22 to get the system voltage. */> > +	numerator = <222>; /* 200 + 22 */> > +	denominator = <22>;> > +};  > > While I already got a reviewed-by from Rob, and maybe I shouldn't be> stirring the pot, but I had an umpteenth look and I now think this> one looks a bit odd. It shows a bit that it originates from when the> compatible was the very generic "io-channel-unit-converter" in v1> of the series. What I mean is that a voltage divider presumable always> gets you a lower voltage. Therefore, one would assume that the> denominator should be larger than the numerator. The fact that this> translates into the inverted fraction when calculating backwards> through the voltage divider should probably not affect the binding.> > So, in the above example, I think it would make more sense to have> > 	numerator = <22>;> 	denominator = <222>; /* 200 + 22 */> > (and then, naturally, adjust the driver to invert the fraction)> > Comments?Agreed - it is odd as we currently have it.  I wouldn't havea particular problem with renaming this compatible as voltagescaler (voltage multiplier has a specific meaning we should avoidstepping on!)  Anyhow, either way is fine with me, but I agreethe current version is odd.Jonathan> > Cheers,> Peter> --> To unsubscribe from this list: send the line "unsubscribe linux-iio" in> the body of a message to majordomo@vger.kernel.org> More majordomo info at  http://vger.kernel.org/majordomo-info.html`

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