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+--- Thread: Modbus device disconnected but can be read from read test (/showthread.php?tid=4718)
Modbus device disconnected but can be read from read test - khalil - 17.04.2023
Hello Dear,
I have a disconnected Modbus device, but when I try to read from Read Test its give a value.
the error log gives: read failed: operation time out.
please see attached image
RE: Modbus device disconnected but can be read from read test - Daniel - 17.04.2023
Try increasing timeout, should help
RE: Modbus device disconnected but can be read from read test - khalil - 18.04.2023
(17.04.2023, 11:35)Daniel Wrote: Try increasing timeout, should help
Hello @ Daniel
unfortunately it didn't help.
could it be a grounding/wiring issue!
while all the Modbus devices shown in the previous attached image are in the same loop!
RE: Modbus device disconnected but can be read from read test - Daniel - 18.04.2023
Correct wiring is always important as this can create noise. Increase the pool interval for all devices, start from 60sec.
RE: Modbus device disconnected but can be read from read test - khalil - 04.05.2023
Hello dears
If I have a profile but some addresses are not connected, then does these non mapped registers polled?
RE: Modbus device disconnected but can be read from read test - admin - 04.05.2023
Entries without mapped objects are not polled.
RE: Modbus device disconnected but can be read from read test - khalil - 04.05.2023
(04.05.2023, 13:09)admin Wrote: Entries without mapped objects are not polled.
thank you admin
another question
how the SL,LM poll mapped registers one by one or as a group.
if it pulled one by one, is it possible to make a group poll to decrease the traffic?
please advice regarding these errors,
two Modbus RTU devices keep connecting and disconnecting
RE: Modbus device disconnected but can be read from read test - admin - 04.05.2023
Profile can be modified to use a single block read by setting read_count / read_offset parameters.
See these threads:
https://forum.logicmachine.net/showthread.php?tid=4687&pid=30319#pid30319
https://forum.logicmachine.net/showthread.php?tid=2995&pid=19268#pid19268
As for connection issues you might need to add read_delay to the profile.
RE: Modbus device disconnected but can be read from read test - khalil - 04.05.2023
Many thanks admin
Will try and see
Edit:
I added the read_delay to one profile and the device connection issue solved.
Should I add the read_delay to all devices, or only to those showing connection error?
Also, If you could describe how the read_delay work, and how it solve the connection issue?
RE: Modbus device disconnected but can be read from read test - Daniel - 09.05.2023
LM is just waiting before sending new read request. Some slaves do struggle to answer quick requests. If you have same devices then I would add this to all of them.
RE: Modbus device disconnected but can be read from read test - khalil - 11.05.2023
(09.05.2023, 09:14)Daniel Wrote: LM is just waiting before sending new read request. Some slaves do struggle to answer quick requests. If you have same devices then I would add this to all of them.
Thank you Daniel