🧊 Comimark PCF8574 PCF8574T: I2C 8 Bit IO GPIO Expander Module for Arduino & Raspberry Pi (3Pcs) Review

This expansion module was exactly what I needed to add more functionality to my single board computer. It was easy to install and works flawlessly. As my tests showed, it doesn't cause any performance issues or system crashes. The build quality is impressive and it comes at a very affordable price. The only downside is that it took a while to arrive, but it was worth the wait. Overall, I highly recommend this module to anyone who wants to expand the capabilities of their computer.

Bought 6, tried 3 so far, everything works fine. They appear in I2c starting at address 0x20, and each requires a separate declaration in Arduino. This is very handy when you need multiple inputs connected: I need 24 to read the array of hall sensors for the weathervane sensor. The 3144 reverb pickups are open collector, but I didn't use pull-up resistors in prototyping, although I was prepared, they have no problem registering Hi/Lo inputs, at least good enough for my purposes . I poll three…

These extenders work great once you figure out the address. On the Arduino, the default address is 0x20, not 0x40 as some datasheets state. This is because in the datasheet the R/W bit is considered the first bit and the Arduino ignores this bit, so the address is divisible by 2. So if you change the jumper from A0 to VCC, the address in the Arduino will be 0x21, not 0x42 like in datasheets.