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

Dan,

Thanks for the detailed info.  Unfortunately, I'm still in the stumped department on this one.  I was hoping you'd throw me some kind of bone, like, "Oh, I have a 386-33 with 2MB of RAM running Windows XP."  You know, something easy for me.  You are definitely doing all the right stuff with regards to this machine.  

I do know that [i]something[/i] changed between Win2K and WinXP with regards to the way the OS handles the serial port.  What changed?  Not a clue, but virtually all the problems with the SxKey and serial communications come from folks running WinXP.  The SxKey is very sensitive about expecting a steady stream of communication, even when it's just sitting idle.  It has a pretty short timeout period built in to it.  I believe the idea is to keep the SxKey responsive when there is a timeout.

My personal opinion is that somehow MS gave the serial port lower priority in WinXP, causing momentary data hiccups which cause timeouts.  This line of reasoning is how I discovered that lowering the FIFO settings helped.  With a large FIFO, the serial chip waits until the buffer is full before notifying the OS that it's ready for more data.  This is fine when you have more data to send than the size of the FIFO as you're always filling it completely.  However, when you go below that threshold, the serial chip has a timeout built into it that tells it to go ahead and notify the OS even though it's below the FIFO setting.  Lowering or eliminating the FIFO reduces or removes this time delay, resulting in smoother data delivery.

The hardest thing about trying to fix these problems remotely is that I have a completely different setup than you which doesn't exhibit any of these behaviors.  Here's a long shot - is there any way for you to send me a working version of your PCB that exhibits this behavior?  It would be returned, of course.  I would also need some bit of software, it could be as simple as toggling an LED, as long as it causes your machine to barf when walking.  I know this may be impossible, but short of you sending me your computer, I don't know how much closer I can get to replicating your problem.  If this is not possible, I understand, but it seems to me that if three different machines with different serial ports and OS versions all have the same problem, then the least common denominator is either your key or your board.  I would love to be able to find out if I'm barking up the wrong tree or not.

[list]Thanks,
PeterM[/list]

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