MCP23017 GPIO Expander Driver (I2C)

The module sequences initialization and cyclic reads of an MCP23017. The I2C controller is provided: the FSM to complete only exchanges command and acknowledgement signals with it.

Behavior

• first_init='1' selects the initial configuration phase; the FSM then waits for i2c_done.
• start='1' starts a read and keeps start_i2c='1' until the transaction completes.
• After i2c_done='1', the FSM waits 125,000 clk cycles, which is 500 µs at 250 MHz.
• get_data_done pulses during the final acknowledgement state, then the FSM returns to its waiting state.
• reset_n='0' restores the FSM and counter to their initial state.

Refer to the official MCP23017 documentation for the device registers and I2C protocol.