Hope I got the right forum category here.
How far can a PCF8574 I2C expansion boards be away from the Arduino board for communication to work? My idea is to connect light multiple switches (Or other goodies) to the expansion board which communicates with an Arduino nano with max 25-30m of 2x2x0.8 twisted KNX cable for a home automation system. Voltage supply is not the issue as I will be using >12v with regulators at each expansion board.
example board: 20pcs pcf8574 pcf8574t i/o for i2c iic port interface support cascading extended module expansion board high low level geekcreit for arduino - products that work with official arduino boards Sale - Banggood.com