| Message ID | 20180423210809.29586-3-peda@axentia.se (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
On Mon, Apr 23, 2018 at 11:08:07PM +0200, Peter Rosin wrote: > An ADC is often used to measure other quantities indirectly. This > binding describe one cases, a "big" voltage measured with the help > of a voltage divider. > > Signed-off-by: Peter Rosin <peda@axentia.se> > --- > .../bindings/iio/afe/voltage-divider.txt | 53 ++++++++++++++++++++++ > MAINTAINERS | 1 + > 2 files changed, 54 insertions(+) > create mode 100644 Documentation/devicetree/bindings/iio/afe/voltage-divider.txt Reviewed-by: Rob Herring <robh@kernel.org> -- 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
On Fri, 27 Apr 2018 09:29:17 -0500 Rob Herring <robh@kernel.org> wrote: > On Mon, Apr 23, 2018 at 11:08:07PM +0200, Peter Rosin wrote: > > An ADC is often used to measure other quantities indirectly. This > > binding describe one cases, a "big" voltage measured with the help > > of a voltage divider. > > > > Signed-off-by: Peter Rosin <peda@axentia.se> > > --- > > .../bindings/iio/afe/voltage-divider.txt | 53 ++++++++++++++++++++++ > > MAINTAINERS | 1 + > > 2 files changed, 54 insertions(+) > > create mode 100644 Documentation/devicetree/bindings/iio/afe/voltage-divider.txt > > Reviewed-by: Rob Herring <robh@kernel.org> Same white space issue. Fixed. Applied to the togreg branch of iio.git and pushed out as testing. Thanks, Jonathan -- 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
diff --git a/Documentation/devicetree/bindings/iio/afe/voltage-divider.txt b/Documentation/devicetree/bindings/iio/afe/voltage-divider.txt new file mode 100644 index 000000000000..afb52ce77c27 --- /dev/null +++ b/Documentation/devicetree/bindings/iio/afe/voltage-divider.txt @@ -0,0 +1,53 @@ +Voltage divider +=============== + +When an io-channel measures the midpoint of a voltage divider, the +interesting voltage is often the voltage over the full resistance +of the divider. This binding describes the voltage divider in such +a curcuit. + + Vin ----. + | + .-----. + | R | + '-----' + | + +---- Vout + | + .-----. + | Rout| + '-----' + | + GND + +Required properties: +- compatible : "voltage-divider" +- io-channels : Channel node of a voltage io-channel measuring Vout. +- output-ohms : Resistance Rout over which the output voltage is measured. + See full-ohms. +- full-ohms : Resistance R + Rout for the full divider. The io-channel + is scaled by the Rout / (R + Rout) quotient. + +Example: +The system voltage is circa 12V, but divided down with a 22/222 +voltage divider (R = 200 Ohms, Rout = 22 Ohms) and fed to an ADC. + +sysv { + compatible = "voltage-divider"; + io-channels = <&maxadc 1>; + + /* Scale the system voltage by 22/222 to fit the ADC range. */ + output-ohms = <22>; + full-ohms = <222>; /* 200 + 22 */ +}; + +&spi { + maxadc: adc@0 { + compatible = "maxim,max1027"; + reg = <0>; + #io-channel-cells = <1>; + interrupt-parent = <&gpio5>; + interrupts = <15 IRQ_TYPE_EDGE_RISING>; + spi-max-frequency = <1000000>; + }; +}; diff --git a/MAINTAINERS b/MAINTAINERS index 0f7bec878919..4d534c9321de 100644 --- a/MAINTAINERS +++ b/MAINTAINERS @@ -6894,6 +6894,7 @@ M: Peter Rosin <peda@axentia.se> L: linux-iio@vger.kernel.org S: Maintained F: Documentation/devicetree/bindings/iio/afe/current-sense-shunt.txt +F: Documentation/devicetree/bindings/iio/afe/voltage-divider.txt IKANOS/ADI EAGLE ADSL USB DRIVER M: Matthieu Castet <castet.matthieu@free.fr>
An ADC is often used to measure other quantities indirectly. This binding describe one cases, a "big" voltage measured with the help of a voltage divider. Signed-off-by: Peter Rosin <peda@axentia.se> --- .../bindings/iio/afe/voltage-divider.txt | 53 ++++++++++++++++++++++ MAINTAINERS | 1 + 2 files changed, 54 insertions(+) create mode 100644 Documentation/devicetree/bindings/iio/afe/voltage-divider.txt