These are the source files for the PRisme2 bootloader. It's an adaptation of Optiboot, an STK500 compatible, under 512 bytes, bootloader by Arduino.
It makes possible to reprogram the microcontroller's flash memory via UART making it compatible with Arduino IDE.
Compilation is straight forward, but make sure the bootloader is less than 512 bytes or you'll have to increase the bootloader space on the microcontroller via fuse bits to 1024 bytes. The size depends on the compilator's version, compilation is already optimized for size.