Dave Hansen wrote:

> If you're using an STK-200 type programmer, you might try changing the
> buffer.  That generally solved any programming problems we had.

No, I'm using a USB JTAG-ICE (Olimex's). I tried it with the Atmel
JTAG-ICE at work, same results.

GRRRRRRR!!!!!!!

Allrighty... some progress.

Richard H. wrote:

> Now, no knowing why changing CKOPT didn't fix your other ailments.
> Perhaps it caused some damage?

I put an 8MHz xtal on another board, and that brought the swing up to
about 824mV.
With a colorburst xtal, that went up to about 900mV. I figured this was
probably safe to attempt another write operation.

Per a couple of application notes I read from programmer vendors, I put
a 100pF cap between TCK and ground.

Next I tried writing 0x89 to the high fuse byte, and whomp! the swing
when I put back the 16MHz xtal is from 760mV to 4.32V (3.56V) which is
great. I was hoping that this would fix all my programming woes, but it
doesn't.

I tried writing hfuse, lfuse, efuse individually, in that order. Side
effects!!

Write hfuse = 0x89 -> changes efuse from 0xff to 0xfc
Write lfuse = 0xff -> changes hfuse from 0x89 to 0x20
Write efuse = 0xff -> apparently no side effect.

Incidentally, I discovered that the undocumented bits in the extended
fuse byte seem to have a meaning related to clocking! Specifically,
0xFC results in the chip running _incredibly_ slow; while (1) { LED =
^LED; } on 16MHz clock results in blinking at about 4Hz!

BobG wrote:

> I spent several hours searching through the forums here.
> =============================================
> By 'here' do you mean comp arch embedded?, or do you mean 'there'
> (avrfreaks.net)?

avrfreaks.

larwe:
I spent several hours searching through the forums here.
=============================================
By 'here' do you mean comp arch embedded?, or do you mean 'there'
(avrfreaks.net)?

Richard H. wrote:

> that this scope reading means CKOPT is set to a value that does not
> support >8MHz operation.  The CKOPT value that supports 16MHz would
> yield a rail-to-rail swing on the xtal.

Oh yes, I realize this.

> Now, no knowing why changing CKOPT didn't fix your other ailments.
> Perhaps it caused some damage?

I think the problem is that when I tried to set CKOPT correctly, it
wiped the other fuses. At the bottom of all this, I think the
underlying problem is that JTAG programming is really unreliable on
these new parts.

I asked the customer to change the setting on CKOPT, and he said the
values read back didn't match what I would expect (89FF FF).

larwe wrote:
> larwe wrote:
> 
>>assumptions and basically losing hair apace. My circuit is based around
>>an ATmega128, running at 16MHz off an ext xtal. The prototype board
> 
> Well, hmm. I took a look on a scope at work and I'm seeing oscillation
> at exactly the right frequency, with a 554mV p-p amplitude (462mV to
> 1.016V). That's with the 997F fuse settings.
> 
> AVR Studio's fuse dialog is designed to cause confusion regarding the
> CKOPT setting.

Hmmm... maybe the UI is wrong?  I'll be a broken record and point out 
that this scope reading means CKOPT is set to a value that does not 
support >8MHz operation.  The CKOPT value that supports 16MHz would 
yield a rail-to-rail swing on the xtal.

(FWIW, on a Mega128L @ 3.3v & 8MHz, IIRC the low-power osc mode was like 
a 1.5v swing.)

Now, no knowing why changing CKOPT didn't fix your other ailments. 
Perhaps it caused some damage?

Richard

BobG wrote:
> Larwe... this question is asked fairly often on avrfreaks.net.....
> please come read some messages there....

I spent several hours searching through the forums here. I didn't find
anything that seemed even vaguely relevant. Plenty of people asking
about problems with programming, but mostly centered around difficulty
talking to the programmer.

Larwe... this question is asked fairly often on avrfreaks.net.....
please come read some messages there....

larwe wrote:
> assumptions and basically losing hair apace. My circuit is based around
> an ATmega128, running at 16MHz off an ext xtal. The prototype board

Well, hmm. I took a look on a scope at work and I'm seeing oscillation
at exactly the right frequency, with a 554mV p-p amplitude (462mV to
1.016V). That's with the 997F fuse settings.

AVR Studio's fuse dialog is designed to cause confusion regarding the
CKOPT setting.

larwe wrote:

> > If fuse high byte = 0x99, that means CKOPT is the default - unprogrammed
>

> Thank you for pointing this out!

Hmm. Well, I'm tired so I'm going to bed... but this wasn't it. In
fact, programming that fuse has killed the board, I can't talk to it
over JTAG any more :(