At 03:57 AM 4/6/03 -0400, jim barchuk wrote:

>Hardware. Using PICDEM2, has MAX232ACPE, has non-polarized caps on +5,
>C1/C2, and V+/V-. They're the right value but not the recommended type.
>
>That is what concerns me because at higher speeds I get lots of errors and
>at medium speeds I get no (zero) errors.

What kind of capacitors?  If they are the correct value, they will probably
work OK regardless of what kind of cap they are.  The only potential
problem type *might* be a non-polarized electrolytic capacitor.  If they
are ceramic or film caps, they are fine.

>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.

This really sounds like a windows problem and that you are over-running the
UART in the PC.  If you can, try going into the hardware properties of the
UART and setting the buffer value higher.  (get to device manager (Control
Panel --> System --> Device Manager --> Ports --> Com2, select Properties
--> Port Settings --> Advanced.  Move the Receive Buffer slider to a higher
number.)

>I don't want to change them if it's less than likely to fix anything; I'd
>chalk it up to Win and live with the 38k.

If worst comes to worst, implement flow control.  Hardware flow control is
easier to do than software.

An easier solution is to send a packet of characters, pause briefly, then
send some more.  This gives Windows a chance to process the buffer before
it overflows.  Say: 8 characters, wait 1 char time, then 8 more.  Then
start making the packets larger until you see problems and back off to
whatever is reliable.

dwayne

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Dwayne Reid   <dwayner@planet.eon.net>
Trinity Electronics Systems Ltd    Edmonton, AB, CANADA
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