Remote I/O expander circuit

Each of the PCF8574’s eight I/Os can be independently
used as an input or output.

PCF8574
Remote 8-bit I/O expander for I2C-bus
The PCF8574 is a silicon CMOS circuit. It provides general
purpose remote I/O expansion for most microcontroller
families via the two-line bidirectional bus (I2C).

The device consists of an 8-bit quasi-bidirectional port and
an I2C-bus interface. The PCF8574 has a low current
consumption and includes latched outputs with high
current drive capability for directly driving LEDs. It also
possesses an interrupt line (INT) which can be connected
to the interrupt logic of the microcontroller. By sending an
interrupt signal on this line, the remote I/O can inform the
microcontroller if there is incoming data on its ports without
having to communicate via the I2C-bus. This means that
the PCF8574 can remain a simple slave device.

Address of PCF8574 can set at pin A0,A1,A2

slave addresses.