I/O or input-output interfaces allow the processor in a drone or robotic vehicle to communicate with the outside world or other parts of the system. This communication may be with sensors and payloads, drone autopilots or electronic speed controllers (ESCs), external storage, actuators for flight surfaces, and a variety of other devices.
I/O interfaces may be built into the computing system or may take the form of pluggable modules that expand the I/O capabilities of processor boards and single-board computers (SBCs) built around standard form factors such as PCI/104e or COM Express. They may include a variety of ports and interfaces for standard connectors such as USB, micro D-sub or MIL-DTL-38999 military circular connectors.
I/O interfaces may provide communication via analogue or digital signals. Analogue inputs may come from sensors that measure environmental factors such as temperature or pressure, and analogue outputs may be required to communicate with devices such as control actuators for flight surfaces, antenna platform steering or fluid hydraulics. Since computers operate with digital signals, analogue I/O interfaces and modules require built-in analogue-to-digital and digital-to-analogue convertors (ADC and DAC).
Digital I/O systems may provide communications via a wide range of protocols. Serial protocols include RS-232, RS-422 and RS-485, which differ in the number of commanding and listening devices per port and the maximum length signals can travel. Other common protocols include PWM (pulse width modulation), UART, I2C, USB and CANbus.
I/O interfaces may also be used to connect hardware-in-the-loop (HIL) systems during the testing of drone and unmanned system designs. These systems allow real-time simulation with realistic signals that mimic those that would be utilized during actual operation.