Introduction to the I/O Expander

This project was about developing and manufacturing my first PCB, an I2C I/O expander board carrying a PI4IOE5V6416 16-channel I/O expander from Diodes Inc. Linked here.

The board features two solder pads, JP1 and JP2 which are for v-bus and I2C address selection respectively.

The only other IC on the board is the LDO linear regulator I chose, the LP5907, which gives the I/O expander IC it’s 3V3 rail from 0-6V, which is pretty much what we’d find on any Arduino-compatible hardware. I should note this particular version of the board uses 3.3V logic.

Software Support

To go along with the board, I developed a generic C driver for the board. I developed the library in a way that makes it easy for users to implement the board into their specific development environment. Unfortunately, I have not gotten around to developing an Arduino library for this particular board, but I may revisit it at some point.

Users of the library only need to define 4 functions that will control the physical interfaces of the I/O expander, and add those functions to the device handle. The four functions needing importing is the write register function, read register function, reset pin function, and the delay microseconds function.

Referencing the headers for the function pointers goes into more detail about how to implement these functions. More detail can be found in the datasheet for the I/O expander.

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Last Updated: 2024-05-19