PCF8575 I2C 16 GPIO Expander Breakout - Stemma QT / Qwiic Ada 5611 - Adafruit

• It has 16 I/O pins Three I2C address select jumpers mean up to 8 expanders to one bus for 128 total GPIO added Each pin can be an input with light pull-up or an output sink IRQ output will automatically alert you when input pins change value This chip does not have a pin direction register. You cannot set the pins as input or output - instead, each pin has two possible states. Basically, you can think of it as an open-drain output with a 100K resistor pull-up built in. Option one: Lightly pulled up 'input' - by default it will read as a high logic level, but connecting the GPIO to ground will cause it to read as a low logic level. Option two: Strong 20mA low-driving transistor sink output. This means the output is 'forced' to be low and will always read as a low logic level.