Sometimes you need to control more devices than possible with the default address range the device provides. This is possible with an I2C multiplexer e.g. TCA9548 which creates up to eight channels ...

A2. PCF8575C 0x20 to 0x27 need pull up in input mode. See #36, to be verified. So you can connect up to 8 PCF8575 on one I2C bus, giving access to 8 x 16 = 128 IO lines. To maximize IO lines combine 8 ...