PCF8574(4)             FreeBSD Kernel Interfaces Manual             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.

FreeBSD 13.1-RELEASE-p6        November 6, 2021        FreeBSD 13.1-RELEASE-p6