AVR JTAG programmer choice

I bought the Olimex USB JTAG. It is really a serial JTAG with a
USB-serial adapter inside it, of course. It is cheap, it works exactly
like a regular JTAG-ICE (mk.1), I can't fault it. However you should
note that the documentation is not exactly right, and there are some
things I don't completely understand:

* adapter is target-powered despite being described as "USB-powered".
* you MUST have Vref connected on the JTAG interface, and it must be
connected to some nonzero voltage on your target.

our AVR-USB-JTAG have opto-isolatation between USB and target, this is
why you have to feed power from target too :)

the good news is that this way you can debug safely targets which are
running on 220VAC


Best regards
Tsvetan

tusunov@my-deja.com wrote:


Right, I do understand this - but the documentation is a little bit
confusing.

I think it says that both pins 7 and 4 need to be connected to the same
voltage but I thought that pin 7 was the actual power and pin 4 was just a
signal? Therefore, for example, 5V on 7 and 3.3V on 4 would be OK?

Rog.

If you are going to use DebugWire (standard on all newer chips with low
pincount), the MKII is your only choice. Plus it handles USB at full speed
natively (Philips USB controller connected to one of the two Mega128)
without having to go through a serial bottleneck.

So it has it's price, but it's worth it. At least for me.

Mit freundlichen Grüßen

Frank-Christian Krügel

How reliable are the AVR's flash?
I have two Atmega169 (in AVR butterfly) failing.
They are supposed to last 10,000 cycles.
And yet, one failed after hundreds of cycles
and the second failed exactly after one cycle.

I can't program either one of them anymore.
The first one refuse to verify and the second
one verified but still contain the previous version.

If it's so difficult to program them, perhap I should
switch to PLCC (44 pins) socket rather than MLF (64 pins).

linnix wrote:


How are you reprogramming them? What's the power supply?

I haven't had this problem, though I don't use that specific part.

larwe wrote:


In self programming mode (boot loader),
both with the on-board 3V battery and external 5V supply.
We might need to switch to an external programmer.

The second sounds unlikely : ie How can it verify the wrong code ?

If they are not secured, you should be able to read back the code, and
then compare with the nearest HEX version - that can give an idea of
failure modes.

-jg

Jim Granville wrote:


That's what I did.  The read back file (using the same
programmer, avrdude) is different from the new file.
Although I don't have the old version to compare,
the AVR is still running the older code.

I know the bootloader first store it in SRAM (1K),
but it could not have stored the whole file (10K).
The only thing I can think of is that the flash has
a long term memory (old file) and a short term
memory (new file).

We might have to reconsider the bootloader in
general and atmega169 in specific.