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[avr-chat] Debugging an xmega with the AVR Dragon
From: |
Graham Davies |
Subject: |
[avr-chat] Debugging an xmega with the AVR Dragon |
Date: |
Sat, 09 Apr 2011 10:15:29 -0400 |
As previously posted, I am bringing up my first xmega project using an
ATxmega32A4. This is mainly an informative post, but I would welcome any
discussion.
It took me quite a lot of poking around on the Internet to figure out how to
connect the PDI interface of the xmega to the AVR Dragon. Atmel give a
recommended pinout for the PDI connector, which is similar to the ISP
connector, and tell you how to wire it to the JTAG connector of the JTAGICE
Mk II, but although they say the Dragon can be used for PDI they don't tell
you how to wire it up. It turns out that you don't connect to the Dragon's
JTAG header, but you connect to the 6-pin ISP header, just as if you were
using ISP, but not connecting pins 3 and 4. This is fairly convenient as
you can use a ribbon cable and either cut the middle two wires or not
connect the pins at the target.
However, the build-load-run cycle is quite slow as compared to using JTAG
with the mega family. My program is presently a mere 2192 bytes, and:
- Starting debugging takes five seconds before the Run button appears.
- Breaking execution takes four seconds before the Run / Stop buttons
appear.
- Stopping debugging takes four seconds before the Start button appears.
- Changing a register value takes four seconds.
This may not seem much, but I am used to faster cycles and I'm finding these
pauses intrusive.
It is hard to figure out whether to connect a pullup resistor at the RESET
input to the xmega. This is something I habitually do with the mega, using
a value around 100 kohms. However, there is Atmel material advising against
this, with no mention of what values might be permissible or advisable.
There is other material recommending a pullup and giving a startlingly low
minimum value of just a few kohms.
Does anyone have any experience in this area? Could the omission of the
RESET pullup be having some bad effect, like causing communication errors
that result in the long turnaround times?
Graham.
- [avr-chat] Debugging an xmega with the AVR Dragon,
Graham Davies <=