VISA sometimes duplicates data on serial communication using viWrite
Achim L.
after an upgrade of our VXI embedded controllers Type VXIpc-871 from
the original NI-VISA 2.0.5 to NI-VXI 3.3.1 / NI-VISA 2.6.1 we noticed
sporadic transmission problems on a serial interface using the
viWrite() function.
On about 5-10% of all telegrams the user data is sent with 2-3
duplicates. E.g. sending a string like "XYZ" using CR (0x0A) as
termination character, viWrite
normally produces this: XYZ CR
but sometimes that: XYZ XYZ CR CR
and occasionally that: XYZ XYZ XYZ CR CR CR.
Even a program change to inhibit automatic termination character
insertion and doing that manually, changed the behavior to this: XYZ
CR
but sometimes that: XYZ CR XYZ CR
and occasionally that: XYZ CR XYZ CR XYZ CR
Interesting to know, that viWrite reports the correct
number of bytes actually written. I.e. in this example always 3.
Additional information:
Data format on ASRL2:115200,8,N,1
HW-Handshake: RTS/CTS
Flush Out buffer: on every access
OS: WinNT4.0
Does anybody know, if there is a patch, workaround or a newer VXI/VISA
version for embedded controllers available?
TIA
Achim Lott, MICRONAS GmbH
JoshuaP
currently 3.2.
If the problem still persists, run NI-SPY while your application or
test is running and exhibiting the problem. Hopefully, the spy file
will give you a little insight on what the problem might be.
-Josh
Achim L.
in deed - that solved the problem.
I would suggest to update the VXI download page,
where the old VISA2.6 is included:
Best regards,
Achim