John Nall wrote:
> (In the meantime I'm going to try a couple
> of 100 pF caps, which I do have on hand, and see what that does).

I didn't mean 47pF to be an exact value.  100pF is fine, just don't go any
bigger.  Adding 100pF caps will definitely tell you whether the problem is
PGC/PGD crosstalk or something else.  With 100pF on each line, I think
crosstalk can be eliminated as a cause of failure.

Unfortunately if the caps don't fix the problem, the remaining culprit I can
think of is the 220uF cap C9 which might act like it's on Vdd depending on
how the regulator VR1 works.  The only way to get around that without
changing the hardware is to change the Vdd on/off wait times in the EasyProg
firmware.  They are currently both set to 25mS.  The source code is
available, so you could make your own version with longer wait times.

Unfortunately ICSP is not something every circuit it suited for with every
programmer.  These things are best considered up front when the circuit is
designed.  Of course in this case you didn't have that option since the
circuit came from elsewhere.  If I had designed this, I would probably have
stuck a diode between C8 and C9 and not put a full wave bridge on the front,
just a blocking diode.


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