AVR-Chat

--- In AVR-Chat@yahoogroups.com, Dave VanHorn <dvanhorn@d...> wrote:

> I haven't looked inside, but my
> entire use of the Olimex units
> so far has been at 3V.

My Olimex JTAG ICE used an ATmega16, which is only specified down to 
4.5 volts. Now, in practice it is quite possible that an ATmega16 works 
down to 2.7 volts just as well as an ATmega16L. But, do you want to 
rely on that for a piece of diagnostic equipment that should be beyond 
reproach? Is it good design practice to run an ATmega16 at 3 volts? You 
may have an Olimex JTAG ICE with an ATmega16L or you may be running an 
ATmega16 outside its specified range and not know it.

The procedure to load the Atmel software in my Olimex involved taking 
the damned thing apart. This is how I discovered the above. If I hadn't 
noticed the MCU type, I would never have known it was not specified for 
use below 4.5 volts. I do not now trust Olimex as a supplier.

While I had the thing in pieces, I inspected the PCB layout. I have 
never seen worse. Ground and power were treated just like any other 
signal and routed all over the place. Again, is this what you want to 
be in the position of trusting while you're debugging sensitive or 
noisy equipment?

I'm not saying you should toss out your Olimex JTAG ICEs. If you're 
happy with them I suppose that's all that counts. I don't know what I 
am saying, really. It just bugs me that a piece of sloppy design like 
this succeeds in the market as well as painstaking and correct design 
because, well, I suppose for the most part it does seem to work.

Graham.