What is GPIO and how is it used in embedded systems?

GPIO (General Purpose Input/Output) pins are digital pins on a microcontroller that can be configured as either inputs or outputs through software. As input: Read digital signals (HIGH/LOW), detect button presses, read sensors. As output: Control LEDs, drive relays, generate control signals. GPIO characteristics include: Configurable direction (input/output). Pull-up/pull-down resistor options. Interrupt capability on edge or level changes. Maximum current ratings (typically 10-25mA). Voltage levels (3.3V or 5V logic). GPIO programming involves setting direction registers, reading/writing data registers, and configuring pull resistors and interrupts.