Part of programming stand-alone ATmega chips is setting the fuse bytes, these are special settings that can be used to change how the ATmega chips operate.
Some of the things you can do by changing the value of the fuses include;
- select different clock sources and change how fast the chip runs,
- set the minimum voltage required before the chip works.
- set whether or not a boot loader is used,
- set how much memory is allocated to the boot loader,
- disable reset.
- disable serial programming
- stop eeprom data being erased when uploading a new sketch.
There are many articles online but I could not find a single source that brought all the information together and fully explain what the fuses actually do.
It is important to remember that some of the fuse bits can be used to lock certain aspects of the chip and can potentially brick it (make it unusable). However, with a bit of care it is fairly straight forward to understand and use the fuse settings.
Disclaimer, I am relatively new to programming fuses and these are notes I wrote to help me remember things. The information is based on the data sheet for the ATmega chip, internet searches, and questions I asked on forums (especially the Arduino forum).
