| 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>; |
| }; |
| }; |
