Re: [avr-chat] How to program fuses with avrdude

[Juergen Harms]

In addition to the lfuse settings described by Joerg, I suggest you have 
a look at the CKOPT bit of hfuse: I read in the processor manual that 
this bit should be programmed to 0 for clock speeds above 8 MHz.

Maybe some remarks from the "frog-perspective" can be of help - I am 
just going through the starting-at-zero experience myself.

I decided out of pure defensiveness to invest in a JTAG - that should 
allow working with a CPU whose clock has been lost and to rewrite its 
fuse bytes to meaningful values (hfuse=0x99, lfuse=0xe1 for the on-chip 
1MHz RC oscillator of an ATmega16). On the other hand, although I will 
end up with an ATmeqa32, my initial experiences are made with an 
ATmega16 - much less expensive to throw away by the dozen (so far 
theory, touch wood ...).

I went very slowly initially: although I intended to go for a 14.474560 
crystal, I stuck to the internal 1 MHz clock until (a) I felt at home 
with using avrdude and (b) having read the relevent parts of the 
processor manual sufficiently often to be safe when defining the fuse 
bytes. For my high-speed crystal (crystal, not oscillator!), they are 
0x09 (hi) and 0xe0 (lo).

And, have you had a look at the interactive mode of avrdude (-t option)? 
very helpful when you want to know what is going on and just need to 
know whether the CPU is still responding.

Good luck! Juergen