I'm puzzling through the fuse settings in Arduino 13 and have some questions.
The Boards.txt for the Dicimila / Duemilanove however describes the fuse settings as: (rearranged for consistency
diecimila.bootloader.extended_fuses=0x00 diecimila.bootloader.high_fuses=0xdd diecimila.bootloader.low_fuses=0xff
When I burn the Diecimila 168 bootloader from Arduino and read it in AVR studio, it reads as Extended: F8 High: DD (2.7V brownout) Low: FF
The high fuse difference is explained by just a difference in brownout detection. What explains the difference in Extended Fuse setting? I remember reading somewhere that AVRdude has a quirk about the high byte in the extended fuse, for some reason.
I guess the main question is: Is the fuse for 1024 words in boot flash set? This would accord with the bootloader requiring about 2k, which is documented somewhere else.
And is the BOOTRST=0 fuse set. It would seem so since 0 equals set. So the question is mostly about the boot flash section size.
The 328 settings contain another mystery. When I burn the 328 bootloader with Arduino 13 in which the settings are listed in boards.txt as:
Extended: 0x05 High: 0xDA Low: 0xFF
and read them back into AVRstudio, I get
Extended: 0xFD High: 0xDA Low: 0xFF
The extended fuse setting now only controls brown out detection so the 2.7 volt setting is the same as the previous setting.
However the High fuse setting of DA corresponds to a setting of "512 words" instead of the previous setting of 1024 words - I'm writing to ask if this is correct? AVR studio reports that the 1024 word setting should be "D8" (if BOOTRST is also set as before).
It would be nice to see some discussion of the fuse settings (and the design thinking behind choosing various settings). For example, the Lilypad and Nano both have their own settings and some explanation of the rational behind these settings would be welcome.
I'll be happy to document the fuse settings in AVR studio, and write up this information on fuse settings. Having some answers to the design questions though would make it a much more valuable writeup.
I found a page where LadyAda had started some discussion on fuses but seems to have run out of steam. She also didn't discuss the choices made in the Arduino.
As a tip for those burning quantities of chips, AVR studio is much quicker and provides superior feedback in burning bootloaders onto chips.