PCF8574T GPIO EXPANDER
I2C GPIO Extender module, you can use two of the module to extend 8 GPI/O.
Supports cascading, and you can use at most 8 modules to extend 64 I/O at the same time.
I2C Address can be changed by DIP switch setting
All switches to ON position , default address 0x27
When you run out of pins on your Arduino or NodeMCU. This "GPIO (General Purpose Input Output) pin extender" provides an additional 8 pins (P0 ~ P7)
which can be used to 'output a signal' or 'read a signal as an input'.
These modules have address on the I2C bus, and if daisy-chained you can connect upto 8 of these devices in a project.
Each device will give us an additional 8-bits of GPIO enabling 64 GPIOs in total.
The Address range of PCF8574 is from 0x20 to 0x27 (7 bit address mode). at the max 8 of these devices can be connected in a project to the I2C bus.
The included 'Wire Library' allows to communication over the I2C/TWI bus of Arduino, however if you want you can also download and use
the 'PCF8574_library' from github: