jim barchuk <jb@JBARCHUK.COM> wrote:
> At 115k the first line *always* drops several of chars *before* the first
> CRLF. Never the same chars. The rest of the screen is almost always
> flawless, drops a few here and there, only about 2-3% of full screens have
> an error. But I can induce a few more drops by making Win 'do something'
> such as switching to other windows. I can see behind what I switch to that
> chars are dropped, and capture to log to make sure they really are
> dropped. Overall is obviously not working well.

If charge-pump loading was your problem, you'd see modified (wrong)
characters, not just dropped characters.

No, your problem is Windows, which is anything *but* a real-time
operating system. Windows can ignore interrupts for tens if not
hundreds of milliseconds at a time if it gets "busy" (e.g., clearing
a screen or switching windows), allowing the hardware FIFOs in the
UARTs to get overrun and causing the symptoms you're seeing. You need
some sort of flow control in order to accomodate this.

If you really need to sustain this kind of data rate into a Windows
PC, you might consider switching to USB or even Ethernet. External
serial-to-USB or serial-to-Ethernet boxes should be able to do this
with minimal setup.

-- Dave Tweed

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