The Beta Main Board is the camera's equivalent of a PC's motherboard. It hosts two external medium-speed shield connectors and two high-speed plugin module slot connectors - These act as a central switch for defining where the data that's captured by the sensor and other interfaces gets routed to inside the hardware. In this regard, all specifics can be dynamically reconfigured in software.
In the centre of the Main Board, and on both sides of the PCB, a 'solder-on' area for Beta CSOs has been incorporated. CSOs host sensor chips capable of, for example, sensing the camera's orientation and acceleration (the same chips used to stabilise quad-copters and track head movements in VR headsets). Being situated directly behind the image sensor's centre means that these sensors are ideally positioned to supply data surrounding image stabilisation or metadata about the camera’s orientation and movement during a shot.
The Main Board is positioned between the Interface Board and the Power Board in the camera's PCB stack.
The purpose of the two Lattice FPGAs (the so called routing fabrics) is to handle all the low speed GPIO communications that are required for plugin modules, shields and CSOs without sacrificing valuable Zynq GPIOs.