PCF8574T IO Expansion Board

Functions:
- This is the I/O extended module, which use for I2C interface, you can use two of the module to extend 8 I/O.
- Support cascading, and you can use at most 8 modules to extend 64 I/O at the same time.
- It can be changed the address by set toggle switch
- Every 2 seconds, make P0-P7 port output High level, Low level, and put 3 toggle switches to ON, the address of module is 0x27.