Review on HiLetgo PCF8574 PCF8574T IO Expansion Board I/O Expander I2C Evaluation Development Module (2pcs) by Alonzo Weaver

The boards I received have version "A" of PCF8574. This means that the device address is different. If your code uses 0x20 as the base address, you need to change it. It took me some time to figure that out. EDIT: HiLetgo contacted me after I posted a three star review and offered a partial refund which I accepted. I am updating my rating to four stars based on their customer service and the fact that the boards worked great after I discovered the difference in part numbers and started using the correct address value for version "A" parts. But you should still check your version to see which version you have and refer to the datasheet to find the i2c address associated with that version.