RS422 problem with bs2

Hjehan

We have a STAMP bs2 application that's been running for several years without problems on a 'older' PC IBM300PL.··We communicate with·the PC via port 1 RS232 to a·RS422 converter.· Then one day we change to a faster PC (Dell 755) & all at once we have communication errors.· Specifically, our message consists of 21 characters, the last is a checksum char.· Our problem is that we're now getting frequent check-sum errors.

Any thoughts?

Here's our command to pull in the message:
SERIN PCdataInPin,NormBaud9600,PCReplyTimeout,DecodePCmsg,[noparse][[/noparse]STR PCmsg\21]

One piece of info: We've found that the problem is much less severe if we go into Device Manager and uncheck the FIFO box in the Advanced properties tab for the PC's RS232 port.

Help!

icepuck

What OS where you running before and what OS are you using now?
-dan

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Arguing with myself--sometimes me, myself, and I don't always agree.
(Former) Caterpillar product support technician

Hjehan

Was Windows 2000, now is XP.

allanlane5

What are you running on the Dell to its 422 converter?

Did you also purchase a new USB to 232 adapter, or are you using 'native' DB-9 serial ports on the PC?

Some newer PC RS-232 ports put out lower voltage signals -- these may be confusing your 422 adapter.

Hjehan

We're running the PC's port 1 RS232 (DB-9) into the RS232-to-RS422 converter. The converter is the same one we've been using all along. And now that I think of it we also tried using a RS232 port on a PCI bus card with the same results.

I should also mention that the PC has no trouble reading replies from the STAMP. Go figure...

Yeah... interesting about the voltage. I'm not sure how to check though. But what I can do is

Any thoughts on why the FIFO UART box seems to make a difference?