The PCA9555PWE4: It provides 16 I/O pins configurable as inputs or push-pull outputs, with an interrupt output (INT) that signals the host when an input state changes — eliminating continuous polling.
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Output drive and interrupt — design notes
Each I/O can source 10 mA or sink 25 mA, enough to drive LEDs directly or interface with logic inputs without external buffers. The interrupt output (INT) is open-drain and asserts low when any input pin changes from its programmed state — useful for wake-from-sleep or event-driven firmware. The POR (Power-On Reset) feature ensures all I/O default to inputs at power-up, preventing unintended output states during supply ramp.