This is probably one of the stupidest questions asked here... but what is an I/O expansion board and what is it used for?
Is it used for testing software? Or for connecting between different interfaces?
I was told I will be working with an Arduino micro controller, joystick, lcd screen, servo, and an I/O expansion board for a project and that I need to interface them all together as soon as possible, but I can't figure out how the I/O board is used? Shockingly googling "i/o expansion board" returns very little information.
An input/output expansion board does exactly what it say on the tin.
A microcontroller has a limited number of pins, and hence a limited number of interfaces with the outside world.
An expansion board takes a few of those pins (typically I2C pins) and fans them out to even more pins.
Of course, there are usually trade-offs, like lower switching speeds (because of the I/O overhead of addressing and commanding the additional device)
One IO expander chip I work with a lot is the MCP23S17 from Microchip. It is controller by SPI (they do an I²C version too), which takes 4 IO pins, and provides 16 IO pins. You can optionally use a 5th IO pin to act as an interrupt trigger, so the 16 extra IO pins can do change notification and trigger an interrupt on the Arduino when a change occurs on any of the extra pins.
