Xiaofan Chen wrote:
> Back to the basic, how can OpenOCD to wiggle a pin (forget
> about the PCB Gerber View integration part)? Is this possible?
> I am not so familiar with JTAG. But intuitively I think this is
> already difficult. Without downloading a small program to
> the chips, how do you toggle an I/O pin?
>
>   
Take a look a this introduction:

    http://www.corelis.com/products/Boundary-Scan_Tutorial.htm

The idea is this: If you have a BSDL file, which identifies the JTAG 
commands, the DR scan order (bit order) of all I/O pins... you don't 
need much more.
Step 1: Scan in a zero the pin, Step 2: Scan in a one on the pin, Step 
3: Repeat.

There is no target code involved.

Same method is used to read the pin..

But - back to the "gerber view" - or something like it...  Perhaps a 
chip outline.
Maybe like the Xilinix pin allocation graphic view program.
If you can read all the pins. You can draw "logic 1" pins in one color, 
and 0 in another.
If you keep reading, you could draw "changing" in a different color.

Take that to the next level - ie: Gerber view - and you can make board 
traces blink different colors.

-Duane.





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