FreeBSD/Linux Kernel Cross Reference
sys/contrib/device-tree/Bindings/iio/resolver/ad2s90.txt

     Analog Devices AD2S90 Resolver-to-Digital Converter
     
     https://www.analog.com/en/products/ad2s90.html
     
     Required properties:
       - compatible: should be "adi,ad2s90"
       - reg: SPI chip select number for the device
       - spi-max-frequency: set maximum clock frequency, must be 830000
       - spi-cpol and spi-cpha:
            Either SPI mode (0,0) or (1,1) must be used, so specify none or both of
            spi-cpha, spi-cpol.
    
    See for more details:
        Documentation/devicetree/bindings/spi/spi-bus.txt
    
    Note about max frequency:
        Chip's max frequency, as specified in its datasheet, is 2Mhz. But a 600ns
        delay is expected between the application of a logic LO to CS and the
        application of SCLK, as also specified. And since the delay is not
        implemented in the spi code, to satisfy it, SCLK's period should be at most
        2 * 600ns, so the max frequency should be 1 / (2 * 6e-7), which gives
        roughly 830000Hz.
    
    Example:
    resolver@0 {
            compatible = "adi,ad2s90";
            reg = <0>;
            spi-max-frequency = <830000>;
            spi-cpol;
            spi-cpha;
    };

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