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 | | From: | Mads | | Subject: | Problem using two ports in parallell on cFP? | | Date: | Sun, 23 Jan 2005 19:10:09 -0600 (CST) |
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 | This could be VISA related, or something that should be posted in the Field=
point section, but anyway:
It seems VISA has some problems handling =
communication on two ports at the same time on a compact Fieldpoint 2020 mo=
dule. Quite often I get write errors; VISA reports that it could not write =
to the port. Unfortunately I do not have the error code right here (will po=
st it later), but VISA gets a timeout on accessing the port.
One por=
t (port 1) is busy responding to modbus polls at 9600 baud, the other one (=
port 2) is used to upload large chuncks of data at 38400 baud every now and=
then. (Parallell running VIs, both have normal priority etc.). All the cod=
e is fine and is used without any problems in numerous applications running=
on PCs, however there are some major differenses: First of all the code wa=
s previously based on the serpdrv based serial VIs, these VIs have been rep=
laced with the VISA based compatability VIs from LV 7.1.1. I have not gotte=
n around to testing whether this causes a problem on a PC as well. Secondly=
the code is now run on a cFP 2020. The modbus related port checks the numb=
er of bytes continously and processes incoming messages if a certain halt i=
n the data occurs. As long as there is no modbus commands coming in the sec=
ond port has no problems...
Does this sound familar to anyone? It se=
ems to me that VISA is having problems writing to two ports at the same tim=
e, or perhaps there is some other serial related task that affects the writ=
ing on the second port. Using the compatability VIs is probably not the bes=
t thing to do, but could it cause this type of problem?
I would nor=
mally investigate this a bit more before posting anything here, however I'm=
in a bit of a rush and hope that someone in a different time zone might gi=
ve me some clues before I wake up tomorrow morning...:-)
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