Kernel-4.18.0-80.el8_voltage-divider

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>;
};
};