Custom component for the mcp23017 and mcp23008 i2c port expander ICs.

Highlights of what it does offer

Async implementation (more reactive and nicer to HA)
Thread-safety allows different entities to use the same component
Config Flow support (UI configuration) in addition to legacy configuration.yaml.
Push iso pull model for higher reactivity, e.g. 100ms polling for 'zero-delay' push button without loading HA.
Optimized i2c bus bandwidth utilisation
- Polling per device instead of per entity/8x gain, register cache to avoid read-modify-write/3xgain or rewriting the same register value)
Synchronization with the device state at startup, e.g. avoid output glitches when HA restart.
Compatible with MCP23008 (8 pins) device.

Useful links