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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>;
};
};
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