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

[Joerg Wunsch]

Nuno Santos <address@hidden> wrote:

> Please, can you tell me how to do it on the flY?

Not sure what you mean by "on the fly".  Once the fuse is programmed,
it will remain that way.  After all, it's just another EEPROM cell.

You didn't tell us *what* kind of oscillator you are trying to attach,
so it's hard to guess in particular what startup timing you'd like to
have.  As you're writing it's an external *oscillator*, I don't assume
you'd like to connect just a crystal only but a real oscillator.

According to the datasheet, external clock requires the CKSEL bits to
be all 0, so this the low nibble of lfuse is 0.  For a most
pessimistic assumption about the startup-time the oscillator needs,
selecting 65 ms results in the SUT bits being 0b10.  This gives bits 4
and 5 of the lfuse.  Finally, the two high-order bits of lfuse
determine the state and voltage level of the brown-out detection.
They are disabled by default, i.e. 0b11.  So all together, this makes
0b11100000, or 0xe0.

avrdude ... -U lfuse:w:0xe0:m

-- 
cheers, J"org               .-.-.   --... ...--   -.. .  DL8DTL

http://www.sax.de/~joerg/                        NIC: JW11-RIPE
Never trust an operating system you don't have sources for. ;-)