On 27.03.2015 05:02, Tomas Vanek wrote:
> Do not be so focused to a reset signal on target connecting.
> Reset is not pulsed just because OpenOCD init command fails before
> script reads a reset command.
> Origin of the problem is bad read from DP. Recheck cabling and
> compatibility of cfg and busblaster CPLD.
> I have no experience with busblaster, no more clues from me.
Thanks for all who helped - got it!
As soon as I attached my logic analyzer, the problem went away -
pointing to a signal integrity problem.
The bus blaster has no termination resistors at all between the CPLD and
the debug connector - two 100ohm series-termination resistors in the
SWCLK and SWDIO lines (on the busblaster end) fixed the problem for good.
Now connecting works 100% of the time, and reset also works - it seems
OpenOCD does some SWD transaction *before* pulling SRESET, and that
failed in my case. I am not sure if this can be a problem in case a
reset is needed to get SWD working, but on the LPC8xx, this does not
seem to be the case.
cu
Michael
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