Waveshare MCP23017 IO Expansion Board I2C Interface Expands 16 I/O Pins Stack to 8 pcs for Raspberry Pi Raspberry Pi 4B+ 4B 3B+ 3B 2B+ Zero W WH 2 W Micro:bit Ardui STM32

If you are looking at this review, you probably already know what this board is for, so there is not a lot for me to say about this board. It uses I2C protocol to expand the number of GPIO you have up to 16 more digital inputs or outputs. Here are the most important items to consider:1) This board either requires you to use the DuPont connectors for the I2C lines, or to solder additional headers to the board (currently unpopulated). It’s nice to be able to plug this onto a bread board, but I wish the header pins also had SDA, SCL, and INT. Be aware of this if you are considering this board. The necessary header pins (even unsoldered) were not included, but at least a DuPont to JST connector was.2) I verified by the simplest method possible, which for me was using Arduino IDE to run the sample code provided on the Waveshare website to blink an LED. The tutorials cover Raspberry Pi, STM32, as well as Arduino, and the Arduino tutorial worked for me. They also have the board schematic available, which is nice.3) The I2C address can be changed, but you have to solder the address bits. This is a pain, and I’ve seen other similar boards that include a dip switch for doing this, which is more convenient, but not on this one. And, this board isn’t less expensive for the added inconvenience.Overall, this is a totally decent board for expanding your IO ports via I2C. However, I am knocking off one star for not having the I2C address pins be more easily set. This is a minor inconvenience, but a 5-star board would have included this. I understand there are a lot of clones of this board, but it would have been nice to improve upon a clone with some minor features.

I got this item to use with an Arduino Uno board. As projects get more complicated with trying to integrate more sensor you can find yourself running out of pins very quick. Well this item solves that issue. The board is fairly easy to use with lots of good documentation and videos on how to wire things out to make it work. This item does what it’s meant to do, no issues for me. I would recommend this product.