MCP23017 I2C IO expander breakout board

Posted on Wednesday, March 6th, 2013 in project logs by DP


Jechavarria has designed this breakout board with the MCP23017 I2C IO expander:

With this board you can drive a 2×16 display LCD with only two signals (I2C).

I also develop some code (in C) to manage this device, based on a AT89C51RE2 microcontroller. Please feel free to visit for more info, schemes, and source code!

Via the forum.

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3 Responses to “MCP23017 I2C IO expander breakout board”

  1. Joe Desbonnet says:

    I’ve wondered about the economics of these IO expander ICs: would it not be as cheap (cheaper?) and more flexible to use an full blown MCU to do that task? Ok, you’ll need to write a tiny bit of firmware… but so much more flexibility…

    • Sleepwalker3 says:

      I agree for stuff where you can do the I/O on a larger processor, though if needing a lot of I/O (more than is available on your chosen micro), then these could be handy.

  2. jechavarria says:


    It’s right that you can use a higher processor to do this, but when you’ve a lot of IO’s to manage, I think this kind of solution is better, in terms of connections and processing. Don’t forget that with this device you can have up to 128 IO’s with only two pins!! For a small microcontrollers, this will be very usefull in some applications. And about the software, you’ve reason that it isn’t very flexible, I only try to show how you can work with this device. Obviously, it can be improved. Thanks for your comments!!

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