Re: [avr-chat] avrdude-ATMega32 fuse bits issues

[Brian Dean]

On Sun, Dec 18, 2005 at 02:37:08PM -0800, Chris Pontiga wrote:

> I am having quite a bit of trouble with the fuse bits and I have 4 chips
> which exhibit this issue.  I am able to program the chip with the default
> factory settings and it functions fine.  However, I need to use a 16Mhz
> external crystal.  So I have that hooked up between the two XTAL pins with
> two 22pF caps to gnd.
> 
> I use the following to program the fuses:
> 
> fuse:
>     avrdude -u -pm32 -cbsd -E noreset -U lfuse:w:0x5f:m
>     avrdude -u -pm32 -cbsd -E noreset -U hfuse:w:0xd1:m

The problem could be that you don't have CKOPT programmed.  Without
CKOPT programmed, getting the chip to run at 16 MHz is going to be hit
or miss.  CKOPT enables the full rail-to-rail oscillator swing and is
generally required for speed settings over 8 MHz.

To recover the chip, try feeding an external clock signal (approx 1
MHz TTL square wave) into the XTAL1 pin.  The exact speed is not
critical - you just want to get the chip running.  Re-invoke avrdude
and attempt to enter programming mode.  Reset the high fuse bit to
0xc1 instead of 0xd1.  Then remove the external clock signal and see
if the chip starts by itself after that.

-Brian
-- 
Brian Dean
ATmega128 based MAVRIC controllers
http://www.bdmicro.com/