Review on 📦 NOYITO PCF8574 IO Expansion Board I2C Bus Development Module (Pack of 2) - Enhance I/O Capability Effortlessly by Giovanni Glenn

The definition says it's quasi-bidirectional - a strange term - but if you look at the PIN diagram it all becomes clear. While they're great for OUTPUT (assuming a 1mA source or 25mA sink is sufficient), as an INPUT they fall badly in my opinion. The input must be able to overcome the 1mA OUTPUT enough to reduce the signal level. And your code MUST write HIGH to the INPUT pin before attempting to read. In short, I consider them for OUTPUT use ONLY. They work as an input, but IMO puts a load on the driver circuitry. This applies to any PCF8575 or PCF8574, so be careful when using them.