PCF8574(4)

NAME
pcf8574 - driver for the PCF8574 8-bit I2C IO expander

SYNOPSIS
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"

DESCRIPTION
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>;
    	};
    };

SEE ALSO
fdt(4), gpiobus(4), iicbus(4)

HISTORY
The pcf8574 driver and this manual page was written by Andriy Gapon <avg@FreeBSD.org>.

BUGS
The pcf8574 driver does not support the input change interrupt that the hardware provides.