5 pcs - MCP23017 - i2c 16 Input/Output Port Expander

I used this port expander on an Arduino ESP8285 Development Board DIY project for a pool solar heater and pool water level controller.

Better deal than buying the one chip package.It works great. I am able to use this MCP to expand my I/O pins with ease. I2C is a great interface to work with along with the MCP23017. I suggest looking at the Adafruit MCP23017 library for code examples.Pros:* It works as promised* Solid build* Breadboard friendlyCons:* Not as cheap compare to shift registers but the MCPs are easier to use

A feature rich port expanded with many more capabilities than a simple shift register. Being able to enable a built-in pull-up resister per port is very nice. The interrupt on change feature is great. Accessing via I2C is excellent.On the down-side the datasheet isn’t exactly a paragon of clarity. Many examples of Arduino code don’t really work if you gang several chips together into a bank with a shared interrupt.I recommend the Adafruit library as a good starting point, although I had to modify it to enable a missing command. You really need some sort of hardware probe to see what’s going on in fast changing systems with multiple shared interrupts per second. I recommend the Saleae Logic Analyzer. It saved me when debugging a big system with twelve MCP23017 chips in four banks of three chips each. The system is working great now, but there were a few subtle timing issues that had to be overcome. Also, take a look at the Adafruit TCA9548A if you need more than eight MCP23017 chips in your project. The MCP23017 has only three bits for I2C hardware addressing. The TCA9548A lets you multiplex up to eight I2C busses, enabling you to use up to 64 MCP23017 chips!

If you need more inputs or outputs and can use i2c, this IC is perfect. I used it in a toy project and only had to use two pins on my microcontroller to address six different buttons.

It a chip doing what it does.

Great to use with rpi :)