Has anyone tried the ABB OPC server with open opc?
I am not using the gateway server - direct connection on same computer.
I can write 4 values to the OPC server fine.
I can usually read 1 value fine.
If I read say 4 values, it fails 99% of time (timeout).
Anyone else had this problem?
Are you doing group based reads, or instantaneous reads?
If instantaneous reads, then the likely problem is your group build timeout (ya, i know, sounds confusing, but check it out - everytime you read, you have to create a read-group - so even an instantaneous read will build a group, read the data, then close the group… a group based read will build the group, read the data, leave the group open, wait a little while, read again, wait a little while, read again, so on and so on…)
serial, token ring, or older / congested networks (even some large ethernet networks) will benefit from read calls as follows…
group based -
opc.read(WHATEVER-YOU-WANTED-TO-NORMALLY-READ, group=SOMENAME, timeout=TIMEOUT-IN-MILLISECONDS)
for example -
opc.read(ARRAY-OF-TAGS-TO-READ, group=GROUP_READ_1, timeout=30000)
this will yield a 30 second connection period - the default is 5 seconds I believe. So you can try 15000 (15 seconds), or 30000, but I don't think you'll need more than 60000 even with a horrendous network.
Thanks for the tip - yes I was doing instantaneous reads. I will try group reads and have a go at updating the documentation.
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