The GRETA expansion board for the Amiga 500 computer has SDRAM, microSD mass storage and Ethernet controllers. It is built on FPGA technology. The intended audience is any person who wants to learn more about how to develop hardware for the Amiga computer in general, and especially the one who wants to develop the GRETA expansion further. All schematics, PCB layout and VHDL code described in this document are released under the GNU General Public License, version 3. Gerber files are readily available and can be sent to a PCB manufacturer for production. Refer to the schematic files for bill of materials (BOM). As of January 2014, some features are still to be implemented in VHDL, namely microSD controller and Ethernet MAC, as well as corresponding software device drivers on the Amiga. For a description of the design, se the file doc/greta.pdf. The original author is Martin Åberg. He can be contacted on electronic mail (remove spaces): m ar t in AT f ri p os t DOT o rg