i2c.py 文件源码

def _init_connection(self):
        self.bus = SMBus(self._port)

        if self._i2c_expander == 'PCF8574':
            c.msleep(50)
        elif self._i2c_expander in ['MCP23008', 'MCP23017']:
            # Variable for storing data and applying bitmasks and shifting.
            self._mcp_data = 0

            # Set iodir register value according to expander
            # If using MCP23017 set which gpio bank to use, A or B
            if self._i2c_expander == 'MCP23008':
                IODIR = MCP23008_IODIR
                self._mcp_gpio = MCP23008_GPIO
            elif self._i2c_expander == 'MCP23017':
                # Set gpio bank A or B
                if self._expander_params['gpio_bank'] == 'A':
                    IODIR = MCP23017_IODIRA
                    self._mcp_gpio = MCP23017_GPIOA
                elif self._expander_params['gpio_bank'] == 'B':
                    IODIR = MCP23017_IODIRB
                    self._mcp_gpio = MCP23017_GPIOB

            # Set IO DIRection to output on all GPIOs (GP0-GP7)
            self.bus.write_byte_data(self._address, IODIR, 0x00)