For payload control as well as for the management of the payload data, Flying Laptop is useing a dedicated Payload On-board Computer (PLOC).


The heart of this computer is a Virtex-II-Pro FPGA from Xilinx. It is build into a board, the central processing node (CPN), which was developed and build by the Fraunhofer Institute for computer architecture and software engineering. The use of this FPGA leads to a high parallisation, which is necessary for a simultaneous control of different payloads and for receiving payload data simultaneously.

CPN also has another smaller FPGA, the Spartan 2, for its own management. This FPGA is responsible for the CPN itself and, therefore, not only sends house keeping data but also configures the main FPGA. For the second task it has access to 3 flash chips to save configuration files on them. The usage of a second FPGA allows to still be able to program the main FPGA even after launch.

In addition to the FPGAs the CPN also has elements for intermediate storage of payload data. For this task it has 3 DDR SDRAM chips with each haveing a capacity of 128MB. Also it has access to 4 SSRAM chips with 4.5MB each.

Beside these main features CPN has even more features like a comparator for current monitoring, an EEPROM and a NAND flash.

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CPN not only is responsible for the payload itself but also for the Mass Memory Unit (MMU). This unit is used for saveing payload data. Useing the MMU CPN has access to 2GB flash memory. The MMU was developed, build, tested and programmed at the Institute of Space Systems. The core of the MMU is a ProASIC3L FPGA from Actel.


The combination of CPN and MMU is a complete unit for payload control. Because of redundancy there are two such units implemented in PLOC.

The PLOC's electronic is completed with the Power Board. This board was also developed, build and tested at the Institut for Space Systems. The tasks of this board is primarily to convert the bus voltage to a lower voltage. But it also controlls the start up procedure and the emergency shutdown.


PLOC - CAD Model