> After some more fiddling I found that it would work when
> 100pF capacitance
> was added between either PGC or PGD and ground.

weird weird.

Note that I use my Wisp628 programmer with long wires, with no caps at
the target, with targets in breadboards (both solder and solderless) or
target PCBs. 47 ohms series resistors at the programmer. long ago these
resistors were 470 ohm, I do recall some problems then, that could be
solved with small capacitors, but IIRC at the programmer side. Olin:
maybe retry with lower series resistors, but make sure you switch the
data line to input on reading.

Wouter van Ooijen

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consultancy, development, PICmicro products

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