The PX4 project designed a series of hardware modules used to guide vehicles in both human-assisted and fully-autonomous operation. The currently available modules include the main autopilot (called FMU – Flight Management Unit), platform-specific carrier (called IO – input/output) modules that output servo signals and motor commands and an optical flow camera module.
All modules are CC-by-SA open hardware designs. Notes on commercial hardware offerings and open hardware
PIXHAWK is the all-in-one unit, combining FMU and IO into a single package. With hardware floating point unit and SIMD.