In SX Microcontrollers, SX/B Compiler and SX-Key Tool, VelocitąPaola wrote:

I've encountered a strange problem with my SX-Key Rev. F.  I can't find any similar cases in the forums and Parallax tech support suggested posting here.  Here's the background information:

I have a prototype on the SX28 Proto Board that I've been working on for a few months.  The code for this project previously worked flawlessly both in simulation and in-circuit.  I was experimenting with a few different output drivers and all of a sudden the pins wouldn't respond to what the code dictated they should do.  I figured I must have damaged the chip somehow, so I removed all output circuitry, desoldered the SX28 and re-soldered it.  The problem was still present...

I tried another SX28AC/SS...  eventually I socketed the connection on the board thinking I was damaging the chip with heat (I keep my iron at about 500*F).  Now, even after socketing the connection and swapping about three different SX28AC/DP chips, the problem still hasn't gone away.

 Ok... so maybe it's something I missed on the Proto Board itself: either an inadvertent short or broken trace, etc..  I programmed/debugged the same code into my SX Tech Lite board as well as several bare SX28 Proto Boards.  No matter what, the pins won't react like they should -- like they used to.  For instance, if I tell the RC ports to output a variable containing %0001_0100, it will just output %0000_0000, or sometimes %1111_1111 and still other times just a random (as far as I can tell) combination of pins.  

Again, I haven't changed the code at all and it still works fine in simulation.  

Since, all of the hardware checks out, I think I narrowed down the problem to the SX-Key itself.  The odd part is, is that I can successfully "program" SX chips and I can access the key through HyperTerminal just fine.  Additionally, while programming, I connect the SX-Key first, then apply power, then connect the serial cable.  Has anyone experienced this type of problem before?  Am I correct to think the SX-Key is at fault?  This really puts a damper on the project as I'm trying to get the prototype into testing for an impending release.  

Thanks!

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