Fobu is a key fob sized open-source FPGA + ARM handheld device (formerly VerilogBoy Handheld). The intended usages are portable FPGA retro gaming system (FPGA-based implementation, ARM-based emulation, or both) and portable audio (both general format such as mp3, FLAC, etc. via ARM core and retro VGM such as FM, SSG, etc. via FPGA implementation) player. However, the architecture should allow other usages as well.