So I purchased a new Arduino Uno to solve my problem of accidentally setting my fuses incorrectly and disabling my external reset. I thought I was being very careful too so that was a painful lesson.
Being extra. extra careful, I first read the default values using my Sparkfun AVR Programmer. I received the proper device signature and among other things the line, avrdude: safemode: Fuses OK (H:05, E:DE, L:FF). This is not what I expected based on board.txt file and as echo’d by independent research as to the default uno fuse settings.
I was expected that read of fuses to echo L:FF, H:DE, E:05. As such I am quite concerned I still don’t understand this, since those settings also have external reset disabled among other differences with the expected default fuses.
I am simple trying to change the fuse settings to get a 4.3V BOD. Based on Engbedded AVR Fuse calculator I think I need to run the command avrdude -c usbtiny -p atmega328p -U lfuse:w:0xff:m -U hfuse:w:0xde:m -U efuse:w:0xfc:m
I nervous about doing this since I don’t understand the fuses read back from the out of box arduino uno.