Bob, I suspect that you're correct.

Along that same line, I've redone my test setup considerably so that my pcb
is well grounded and much better shielded from noise.  It seems more stable.
So I can place the ICD2 inside the shielded area, I also bought a new longer
USB2 cable, which I presume has much better impedance control, but I don't
know about its shielding. Ideally, there would be a single point shield on
the USB cable for electric field noise, but that might limit bandwidth.
From a grounding point of view, there is no optimal solution - the ICD2 and
my system under test are on different grounds.  Tying those grounds together
through a heavier cable probably decreases the overall noise given the
ground loop already exists and it's probably a reasonable compromise.  Aside
from the programming voltage, it would be relatively easy to break the loop
with some GMR isolators.  The ICD2 would be powered by the USB and the other
side of the isolator by the system under test.  hmmm

Nevertheless, Microchip has replaced the ICD2.  The new one will be treated
with kid gloves and always handled only when the antistatic strap is worn.
;-)

Ed

-----Original Message-----
From: pic microcontroller discussion list
[mailto:PICLIST@MITVMA.MIT.EDU]On Behalf Of Bob Axtell
Sent: Tuesday, December 16, 2003 10:45 AM
To: PICLIST@MITVMA.MIT.EDU
Subject: Re: [PIC]:Help with ICD2


I just bought an ICD2 as well. I think the issue is that there is only one
thin ground connection between the ICD2 and the device being
programmed/debugged; that puts a lot of noise on that tenuous #24 AWG
connection. As a preventive measure (and normal engineering practice) I
soldered a seperate grounding wire (#20 finely stranded) at the USB
connector shield entrance to the ICD2, and ran it to the ground of my PCB,
using an alligator clip to make a good connection. So I've had no problems
whatever.

--Bob

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