Re: Seeking JTAG emulator for Atmel AT91 ARM Cores on Linux

Johnson wrote:
On Aug 20, 8:09 am, Grant Edwards <inva...@xxxxxxxxxxxxxxx> wrote:
On 2010-08-19, Johnson <gpsab...@xxxxxxxxx> wrote:

Thank you very much for sharing the knowledge! It is really my dream
to use JTAG plus OpenOCD for all purpose: firmware download, boot load
debugging, and application debugging.
JTAG is useful for:

1) Troubleshooting hardware.

2) Debugging bootloader and kernel code.

I'd recommend using the bootloader for firmware download.

Atmel provides already-working bootloaders for their parts.

There's a simple one in masked ROM that's completely bullet-proof. The
only way it won't run is if you do stuff that also breaks J-TAG. You
can download to the one in Masked ROM via serial port or USB.

Atmel also provides U-Boot which knows how to do tftp (as a client)
via Ethernet or various protocols via serial port. There are also
multiple tftp server implementations for U-Boot, but due to
unfathomable opposition by Hr. Denk, none of them are available in the
official source tree.

JTAG is not useful for application debugging.

I certainly need to debug user-space application code, and I
understand it is far from easy.
It's far from easy _if_you_use_JTAG_. It _is_ easy If you use the
tools designed for the purpose.

If I tried not to use multi-threading in my application code, do you
think it will make debug with JTAG + OpenOCD easier?
No.

JTAG is not useful for debugging user-space application code runnon on
Linux.

Running GDB-server on the target and gdb on the development host is
how you do application debugging. That works even for multi-threaded
programs.

BTW, is there any links/Application Notes for debugging with JTAG +
OpenOCD?
--
Grant Edwards grant.b.edwards Yow! NEWARK has been
at REZONED!! DES MOINES has
gmail.com been REZONED!!

Hi Grant, thank you for your reply.

It seems that OpenOCD or Zylin ZY1000 JTAG Debugger can work together
with the JTAG interface, to me it means JTAG can be the right tools
for application debugging. What do you think?


As has already been said here, JTAG is not really very useful for application debugging - its for the low-level stuff.

The point of the ZY1000 is that when you are doing JTAG debugging or downloading, it is faster and often easier to connect than most other JTAG tools. But it is not normally much use in application debugging - JTAG is too intrusive for that. The fundamental issue is that a tool that works by starting and stopping the entire processor is not well suited to a system that is doing lots of things at once.
.

Relevant Pages

  • Re: Seeking JTAG emulator for Atmel AT91 ARM Cores on Linux
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    (comp.arch.embedded)
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  • Re: Seeking JTAG emulator for Atmel AT91 ARM Cores on Linux
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  • Re: Seeking JTAG emulator for Atmel AT91 ARM Cores on Linux
    ... debugging, and application debugging. ... I'd recommend using the bootloader for firmware download. ... JTAG is not useful for application debugging. ... You may also find it helpful when debugging interactions between user applications and kernel code. ...
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