Re: [avrdude-dev] problem with dragon & avrdude, bad signature

[Galen Seitz]

Bob Koutsky wrote:
> Hi,
>
> I'm trying to use avrdude 5.3.1 on Linux (Ubuntu Breezy, avrdude is
> compiled from source), avrdragon in isp mode connected via USB. When I
> try to program ATMega8, I keep getting this error:
>
> $ avrdude -c dragon_isp  -p m8 -P usb -e
>
> avrdude: AVR device initialized and ready to accept instructions
>
> Reading | ################################################## | 100% 0.16s
>
> avrdude: Device signature = 0xff3f00
> avrdude: Expected signature for ATMEGA8 is 1E 93 07
>         Double check chip, or use -F to override this check.
>
> avrdude done.  Thank you.
>
> The value reported as received device signature keeps changing.
> Usually (maybe always), it is composed of various combinations of
> bytes 0x00, 0xff, 0x03, 0xc0, 0x3f, suggesting that there's some
> pattern in how it is generated.
>
> I double, maybe even triple checked the wiring and tried two different 
> avrs.

The mega8 defaults to a 1 MHz clock, which means SCLK needs to be
<= 250 kHz.  I don't have a Dragon board, but it sounds like SCLK
is too fast.  With the STK500, the SCLK period can be adjusted
using avrdude.

galen