MCP23017 4x4 Keypad Library

Published primarily for demonstration purposes.

• Entirely based on interrupts
• Sort of supports multiple simultaneous keys, but not on the same row.

  • Since I have no need for multiples at the moment, this is not something I'm looking into.

    (The issue is that no interrupt is fired on the second press)

• Connect columns to pins 1-4, and rows to pins 5-8 of either bank A or B of MCP23017
• Only tested on esp32, via platformio
• A main objective was to keep the I2C line as quiet as possible
• Depends on: https://github.com/RobTillaart/MCP23017_RT/pull/41