AVR-Chat

I am looking for opinions on JTAG vs DebugWire.

I have an AT90USBKey which hosts an AT90usb1287.
I would like to do single-step debugging on it.

I have found 2 programmers that claim to support it:
1. Atmel JTAG Mk II   at about $90 for a clone
2. Kee Electronics AVR Mk II Lite at about $48 
http://www.keeelectronics.com/AVR_debugWire_ISP_v2.htm

The JTAG Mk II can debug my chip using JTAG.
The Kee product says it will debug my chip using DebugWire.

What are the reasons for me to get one vs the other ?
Beside, of course, $42 :-)

Thanks!

On Fri, Sep 12, 2008 at 05:10:12PM -0000, avrx123456789 wrote:
> I am looking for opinions on JTAG vs DebugWire.
> 
> I have an AT90USBKey which hosts an AT90usb1287.
> I would like to do single-step debugging on it.

What does your AT90usb1287 support? I am not aware of any AVR which
supports both JTAG and DebugWire, but that might be just my ignorance.

> I have found 2 programmers that claim to support it:
> 1. Atmel JTAG Mk II   at about $90 for a clone
> 2. Kee Electronics AVR Mk II Lite at about $48 
> http://www.keeelectronics.com/AVR_debugWire_ISP_v2.htm
> 
> The JTAG Mk II can debug my chip using JTAG.
> The Kee product says it will debug my chip using DebugWire.

If either is a real clone of the Atmel JTAGICE mk-II then it will do
both JTAG and DebugWire. Only $300 for The Real Thing(tm).

The AVR Dragon is very good with both JTAG and DW but only debugs on 32k
and smaller AVRs. Roughly $50 but you have to build your own cables.

-- 
David Kelly N4HHE, dkelly@HiWAAY.net
========================================================================
Whom computers would destroy, they must first drive mad.

Can someone comment on which is better for debugging: JTAG or DebugWire?

At 01:38 PM 13/09/2008, you wrote:
>Can someone comment on which is better for debugging: JTAG or DebugWire?

You DO NOT have a choice. It depends on which chip you are using
whether you use one or the other.

Regards

John Samperi

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Ampertronics Pty. Ltd.
11 Brokenwood Place Baulkham Hills, NSW 2153 AUSTRALIA
Tel. (02) 9674-6495       Fax (02) 9674-8745
Website  http://www.ampertronics.com.au
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Good point.  
I was obviously confused.  
Thanks for pointing me in the right direction.

--- In AVR-Chat@yahoogroups.com, David Kelly <dkelly@...> wrote:
.....
> What does your AT90usb1287 support? I am not aware of any AVR which
> supports both JTAG and DebugWire, but that might be just my ignorance.

--- In AVR-Chat@yahoogroups.com, "avrx123456789" <AvrX@...> wrote:
>
> Can someone comment on which is better
> for debugging: JTAG or DebugWire?

I don't think either is "better".  People have pointed out that once 
you've picked your device you don't have a choice.  You may also have a 
personal preference.  I prefer JTAG, because it's simpler to use.  You 
can do everything through JTAG.  You can even re-program fuses if 
you've messed up the clock selection and the device clock is not 
running.  With debugWIRE, you have to enable it via ISP and go back to 
ISP to change fuses and generally mess around more.  On the other hand, 
JTAG uses up four device pins.  So, for hacking around, I'd recommend 
you get a JTAG device, such as the ATmega16 (which works with the old 
JTAG interface and its clones).  For products, where the cost per unit 
is more important, a debugWIRE device will often be better.

Graham.