Spartan Configurator Bootloader

Alternative to the genuine Alchitry Mojo V3 software:
Caterina bootloder adapted fully to 8 MHz clock and 500 mA of possible current draw.

Build using LUFA 111009.

From their documentation:

To build the bootloader for the ATmega32U4 (Mojo V3 and some V2) use Makefile-v3 (the default). To build the bootloader for the ATmega16U4 (Mojo V2) copy Makefile-v2 to Makefile and run make. This means that Makefile is just a copy of the respective Makefile-v* made before make gets called. Or you call the respective Makefiles directly, e. g. make -f Makefile-v3.

Check the VID/PID combination you use. The ones given are never legally covered by the license and keep property of their respective owners!

While "ISP"ing the bootloader to the Mojo it is recommended to also set some fuses to new values:

LOW = 0xDE
HIGH = 0xD8
EXTENDED = 0xF3

In any case ensure the BOOTRST fuse points to the bootloader section!

After the bootloader is in the ATmega you might want to secure it against accidental overwrites:

LOCKBIT = 0xEF

See also

https://alchitry.com/blogs/tutorials/flashing-the-bootloader

Licenses:

• LUFA = MIT, Dean Camera
• Mojo-Caterina = MIT, Embedded Micro
• My modifications = MIT, René Trapp

Please see respective files for the license details.