Re: Argh. ATmega128 users, please help?


linnix wrote:

worked 100% fine after I tied VREF to +5V; apparently the JTAG
interface isn't happy unless VREF is present.

I wish Atmel would document this, Vref is supposed to be analog related

I'm glad someone else found this problem. I thought I was going mad.
You know, I'm not even sure how I came to the discovery any more. Maybe
I dropped solder on the circuit accidentally ;)

My main question is: do you normally see this micro stop when you
attempt to probe the xtal lines with a scope?

That I would not try to do. Crystal circuits are very sensitive. I
would just verify it indirectly, through internal counters/dividers.

Erk. But I wanted to check the amplitude of the xtal drive. It hasn't
been a problem on other AVR ckts (or other micros) I've built. I was
wondering if there is something magical about the m128.

capacitance on these lines? (I've got about 15pF on both sides of the

15pF to 20pF sounds right. Any other signals/traces near the clock
circuit?

The xtal is <5mm from the IC. Traces run directly from the IC to the
xtal pins, and thence to the caps. Nothing runs under the xtal on the
component side of the board. There is groundplane on the solder side of
the board.

There are some signals running to adjacent pins on the micro, but
there's nothing I can do about that (and they were the same signals on
the previous spin of the board).

- Difficulty programming. Fuses are supposed to be 0x997f 0xff but most

Same here. Programming sometimes work and sometimes don't.

Why, why, why?? I have other h/w on the SPI interface otherwise I would
try ISP instead of JTAG. And why does it work OK on my older boards
(all that I built)? The only difference I can see is that the protos
were built with older chips (date code 0447I) and the finals were built
with date code 0609.

Was I supposed to put my own pullups/pulldowns/whatever on the JTAG
lines?

- Code that works 100% fine on the old board misbehaves on the new
board - specifically I've got some I2C stuff that works OK if I inline

Could be a software and/or compiler problem.

I believe there is some compiler issue - not sure what it is though -
but for this particular case... it's the same HEX file. Works OK on
board A. Fails on board B. What gives?!!

.

Relevant Pages

  • Re: 9.2 Networking/Internet
    ... >> This might be a long shot, but is this the only ethernet interface on ... I have a built in NIC but use a wireless so had to ... > There is a wireless card built in as well. ...
    (alt.os.linux.suse)
  • Re: Decreasing the "standard deviation" of lisp
    ... Numbers are not built from lists of symbols. ... (defparameter four (succ three)) ... Have a look at any Common Lisp compiler (obviously written in Common ... if you can interface to C you can interface to ...
    (comp.lang.lisp)
  • Re: How to use interfaces properly...
    ... When the project is being built, the output directory is cleared. ... interface was not copied back into the output directory leading to it not ... >>> plugin architecture, and I am having trouble figuring out how to set up ...
    (microsoft.public.dotnet.framework)
  • Re: HDTV Owners: Part Deux
    ... the signals properly. ... The truck was demolished, the CO had nary a scratch. ... I know damned well how they are built. ... instantly start low life name calling. ...
    (rec.boats)
  • Re: WiFi at campsites
    ... bought it and, on the advice of knowledgeable friends, I did not get the built in WiFi but got the 'g' card instead. ... The card has more power to retrieve a signal. ... When our daughter visited us in Feb, she could get a bunch of signals I never saw, including the city library over 3 miles away. ...
    (rec.outdoors.rv-travel)