File content as of revision 0:905d325977dc:

// NXP PCA9544A: 8-channel I2C switch with reset

#define PCA9544A_BASE_ADDR_7BIT     0x70
#define MAX_CHANNELS                4

class PCA9544A
{
public:
    /**
    * Constructor
    *
    * @param i2c I2C class servicing the multiplexer
    * @param addr_3bit address of the multiplexer (A0-A2 pin strapping)
    *          Valid values are 0-7
    */
    PCA9544A(I2C * i2c, uint8_t addr_3bit) : _i2c(i2c) {
        _addr_8bit = ((addr_3bit & 0x7) + PCA9544A_BASE_ADDR_7BIT) << 1;
    }

    /**
    * Reset the multiplexer.  All devices connected to the downstream side of
    * the multiplexer are removed from the I2C bus.  Reset is accomplished by
    * deselecting all channels through soft configuration.
    *
    * @returns true if successful
    */
    bool reset(void) {
        const char channel = 0;
        return _i2c->write(_addr_8bit, &channel, 1) == 0;
    }

    /**
    * Enable access to one of the eight devices on the downstream side of
    * the multiplexer.
    *
    * @param channel channel to activate.  Valid values are 0-7.
    *
    * @returns true if successful
    */
    bool select_channel(const uint8_t channel) {
        if (channel < MAX_CHANNELS) {
            char channel_mask = 0x4 | channel;
            return _i2c->write(_addr_8bit, (const char *)&channel_mask, 1) == 0;
        } else {
            return false;
        }
    }

protected:
    int             _addr_8bit;
    I2C *           _i2c;
};