An interface I/O expander is a type of electronic circuit that is used to increase the number of input/output ports available in an embedded system. These expanders allow for more efficient use of the limited I/O ports available in most microcontrollers. By adding additional interface I/O ports, the need for extra I/O components such as additional LEDs, dials, switches, and relays can be eliminated. Additionally, by including an interface I/O expander, more complex embedded systems can be designed, using less overall components. The interface I/O expander itself will typically consist of multiple parallel ports, which can be used to communicate to and from the microcontroller, as well as multiple external devices. Common interface I/O expanders include serial-to-parallel converters, parallel-to-serial converters, shift registers, port expanders and more.