[XCSSA] Oscilliscope help?

[X-otic Computer Systems of San Antonio]

On Sunday 29 March 2009 11:39:59 pm X-otic Computer Systems of San Antonio 
wrote:
> I went ahead and got the Propeller dev kit and working with it has
> been great so far, however I've come up on a problem.
>
> When I'm trying to read PWM signals with my oscilliscope, it shorts
> out the chip and reboots it.  As a test, I used the usb to serial
> "Propeller Key" adapter (which is essentially a USB to 3.3V serial
> adapter)  as a test and kept transmitting while the oscilliscope was
> attached to GND and the Tx pin.

Hmm.. You using the probe's ground alligator clip to connect to the surface 
mount propeller board?  Just "clipping on" to the PCB is usually unstable at 
best.. at worst.. some times you'll short something out.. or even damage the 
traces on the board.  With thru-wire leads.. it easier to clip on.. but not 
so much with surface mount stuff.

What I recommend is actually soldering on a couple of "test point" wires.  
Solid wire for short term testing.  Stranded for longer term hookup points.  
One for GND and one for each test point.  The only example pic that I have is 
this one:
	
http://theweeks.org/toms-stuff/2006-11_Alpha-Geek-Pics/2_Projects-old-and-new.jpg

Examine the center photo of the Info-Globe hack.  Note how the red & green 
alligator clips are hooked up to the IR sniffer.

Also.. might want to consider getting yourself some better hook-type test 
clips for hooking up to things.  Something with clip heads like this:
	http://media.digikey.com/photos/3M Photos/923835-BU-C.jpg
I think that Intertex has them.. but even Rat-Shack has them (in a pinch).


> No snickering... my oscilliscope is a Telequipment D61 and I used to
> have the manual for it somewhere.

Perfectly respectable 10MHz scope you have there.  You just have to make sure 
that you get someone to calibrate it for you every few years. :)

Tweeks