Skip to datasheet
8-bit quasi-bidirectional I²C I/O expander

PCF8574 Basic Circuit

Build a basic PCF8574 circuit with labeled pins, component values and connection guidance.

Package view

PCF8574 in a circuit

One output, one input and an interrupt line.

Physical16pinPCF8574 withA0A1A2ground supply5V bypass andI2Cpullups P0LEDsink P1groundedbutton INTpullup tohost.
P0 LOW lights the LED. P1 remains latched HIGH so the switch can pull it LOW.

Connect it, step by step

Follow the component values and pin connections

Set address and power

Ground the address pins, use a shared 5 V domain and bypass the supply.

Preserve input bits

Write FE for the LED on and FF for off; P1 remains HIGH in either write.

Read the switch

Read bit 1 when polling or servicing INT, and debounce in firmware.

Component view