Manual Pages  — PCF8574

To compile this driver into the kernel, place the following lines in your kernel configuration file: device pcf8574 device gpio device iicbus

Alternatively, to load the driver as a module at boot time, place the following line in loader.conf(5):

pcf8574_load="YES"

The pcf8574 driver provides gpiobus(4) control over 8 GPIO pins. The pins are quasi-bidirectional. Only low output can be actively driven. High output is equivalent to input.

On an FDT(4) based system the following properties must be set:

compatible
	Must be set to "nxp,pcf8574".
reg
	The I2C address of pcf8574.

The DTS part for a pcf8574 device usually looks like:

/ {

        ...
        pcf8574@27 {
                compatible = "nxp,pcf8574";
                reg = <0x27>;
        };
};

fdt(4), gpiobus(4), iicbus(4)