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AdaFruit has a library for the MCP23017 I2C I/O expander chip. You can find it here. Have a look at the readme.md file as that will tell you how to add the files to your Arduino library.
AdaFruit has a library for the MCP23017 I2C I/O expander chip. You can find it here. Have a look at the readme.md file as that will tell you how to add the files to your Arduino library.