code: func (m *MCP23017Driver) Start() (err error) {
  	bus := m.GetBusOrDefault(m.connector.GetDefaultBus())
  	address := m.GetAddressOrDefault(mcp23017Address)
  
  	m.connection, err = m.connector.GetConnection(address, bus)
  	if err != nil {
  		return err
  	}
  	// Set IOCON register with MCP23017 configuration.
  	ioconReg := m.getPort("A").IOCON // IOCON address is the same for Port A or B.
  	ioconVal := m.MCPConf.getUint8Value()
  	if _, err := m.connection.Write([]uint8{ioconReg, ioconVal}); err != nil {
  		return err
  	}
  	return
  }
docs: // Start writes the device configuration.