This is a migrated version of my Wordpress post, written on : 14 Mars 2015
The LPC1114FN28 has two pin ports (0 and 1) that make totally 22 pins (12 for port 0 and 10 for port 1, as shown in the image below). All of these pins could be used as GPIOs. By default, they are all input and pull up-enable (that is each pin is connected to an internal pull-up resistor) except for PIO0_5 (dp5) and PIO04 (dp27) which are "open-drain" (a transistor connects to low and nothing else). Their functionalities can be configured easily by software.
The figure below shows the pin out of the chip, note that each PIOn_m refers to the pin m on the port n.