Spy By Wire with the LaunchPad...

About a year ago I made this stepper controller for my son's rotary 
table on his mill. I used the FET430UIF at the time as I've been lead to 
believe that wires to an off board chip from a launchpad just would not 
work. FET debugging with the FET430 was a real pain as I could not set 
more than one break point at a time with an MSP430G... chip. So this 
time around I figured I would try the launch pad. It was iffy, once it 
worked with 3" leads. Then I put the chip on the launch pad and used 
jumpers to the target project. Then I started having strange problems, 
like the display would crash but the chip would still debug. So I 
grabbed a scope probe to see what the display data and clock looked 
like. It just started working flawlessly. The light in my head finally 
came on.

My 10 volt supply to the target was floating, I've always worked like 
that. The scope has a hard bench ground. With the scope ground connected 
I could not get it to fail.

So I pulled all those annoying wired from the launch pad to the target, 
put the chip back in the target, and hooked up 6" wires to just RST, 
TEST, and ground. It works flawlessly, again. The real problem was 
depending on the USB ground for the signals to the target. using the 
scope without its ground confirmed that the signals from the launch pad 
where 'soft' if you will. With a bench ground to the the target the 
signals were beautiful. At that, the spy by clock is not that fast, 
700ns to transfer.

<http://lakeweb.net/CNC/images/rotary_control.jpg>

I've added a DIR switch and cleaned up the motor power end and put that 
in a box.

Best, Dan.



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Posted by: Dan Bloomquist <[email protected]>
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