The Tetra’s numerous input and output options provide easy-to-implement system communication and peripheral connectivity. Basic on-board features include: Gigabit Ethernet interface with network boot capability, two USB 2.0 host ports, and two CAN 2.0 ports - there are many different protocols available for CAN interfaces. The Yocto build for Tetra includes FlexCAN that implements the CAN protocol according to the CAN 2.0B protocol specification, two I²C ports, one SPI channel with three device chip selects, eight 3.3 V GPIO ports, and up to three Pulse Width Modulation (PWM) outputs. These are shared with the GPIO lines, so use of the PWMs reduces the available GPIO lines. Two serial ports – one port being one 4-wire RS-232 debug port and the second interface is a 2-wire UART port used for local communications and a 6-axis sensor with integrated linear accelerometer and magnetometer. Its functions include: Acceleration event functions: Freefall and motion detection, Transient detection, Vector-magnitude change detection, Pulse and tap detection (single and double), and Orientation detection (portrait/landscape). The Magnetic event functions are: Threshold detection, Vector-magnitude change detection, Autonomous magnetic min/max detection, and Autonomous hard-iron calibration. The on-board mini PCIe card socket accepts a variety of plug-in modules such as Wi-Fi modems, analog to digital converters, GPS receivers, additional Ethernet ports and other small sized plug-in cards for added flexibility. The full size socket provides PCIe and USB interfaces.