{"title":"Adafruit PCF8574 I2C GPIO Expander Breakout","handle":"adafruit-pcf8574-i2c-gpio-expander-breakout","url":"/products/adafruit-pcf8574-i2c-gpio-expander-breakout","description":"The Adafruit PCF8574 GPIO Expander Breakout is an affordable 8-channel I2C GPIO expander that adds extra digital I/O to any microcontroller project. Simply connect over I2C and control up to 8 additional pins for buttons, LEDs, or other digital peripherals — no extra GPIO-rich board required.\n\nThe PCF8574 uses an unusual open-drain architecture — there is no pin direction register. Each pin is either a lightly pulled-up input (100K pull-up, reads high by default) or a strong 20mA ground-sinking output. Arduino and CircuitPython libraries abstract this away, letting you use familiar input/output modes. With three I2C address jumpers, you can chain up to 8 expanders on a single bus for 64 total GPIO.\n\nKey Features\n\n\n8 I/O Pins – Each pin can act as a pulled-up input or a ground-sinking output\n\n3 Address Jumpers – Up to 8 expanders on one I2C bus for 64 total GPIO\n\nIRQ Output – Automatic interrupt alert when any input pin changes value\n\nOpen-Drain Architecture – 100K pull-up inputs and 20mA sink outputs (no direction register)\n\nSTEMMA QT / Qwiic – Solderless STEMMA QT connectors for easy daisy-chaining\n\nBreadboard Friendly – Standard 0.1″ header pinout with mounting holes\n\n\nHow the Pins Work\n\n\nButtons/Switches – Connect one side to the PCF8574 pin and the other to ground. Pin reads high when open, low when pressed\n\nLEDs – Connect the LED anode to positive voltage through a resistor. The PCF8574 sinks current to ground to turn the LED on\n\nDigital I/O – Light pull-up acts as logic high output; strong ground acts as logic low output\n\n\n\nNote: The PCF8574 cannot source current to drive an LED high, and button inputs connected to positive voltage will need an external pull-down resistor. The Arduino and CircuitPython libraries handle the open-drain quirks automatically.\n\n\nIdeal For\n\nAdding extra buttons, switches, or keypads to I2C-equipped boards\nExpanding LED or relay control beyond available GPIO\nMulti-expander setups requiring up to 64 digital I/O pins\nProjects needing interrupt-driven input change detection\n\n\nAlso Consider\n\n\nMCP23017 I2C GPIO Expander – 16 channels with full input/output direction control\n\n\nResources\n\nArduino PCF8574 Library\nCircuitPython/Python PCF8574 Library\nSTEMMA QT Introduction\n","vendor":"Adafruit","product_type":"physical","in_stock":true,"options":[],"variants":[{"id":2023,"title":"Default Title","sku":"AF-5545","price":10.01,"on_sale":false,"in_stock":true,"available_quantity":100,"option1":"Default Title"}]}