Author Topic: Modbus RTU very slow recovery from slave not on line  (Read 455 times)

quadro

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Modbus RTU very slow recovery from slave not on line
« on: April 26, 2020, 10:23:27 AM »
Hi to all,
I noticed that recovery of  communication with slave if interrupted depends on how long slave was off.
That does not make sense to me so I would like to know if others have same issue.
I am using latest beta and have few digital panel meters on form connected to 4 rtu comm drivers.
If I disconnect slave for a few minutes then digital panel meters display new values within about 15 sec while at the same time slave log shows that request started to come same second when it is back on line.
If I disconnect slave for a day (normal situation if you have sensor on maintenance or without power) then when I put back slave on line digital panel meters needs a few minutes to recover and even when they display new values "Read Timeout" is showing on meters for some time and at the same time meters again needs a lot of time to display new values.
After number of minutes everything is again normal.
It looks like there is a big que waiting to resolve and then everything is back to normal.
In slave log I can see that requests are comming as soon as slave is on line.
Digital panel meters are just attached to driver and no event is used in either.
This is a big issue for me since values are changing and there is nothing on meters.
I have timeout set to default 3 sec.
I am not sure if this is a support question or bug report but Archie can decide and give some clue what is going on.
I am expecting that communication recovery is immediately when slave is back on line since slave respond in 200 ms.

Thank you

quadro

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Re: Modbus RTU very slow recovery from slave not on line
« Reply #1 on: May 16, 2020, 06:06:51 PM »
So it seems nobody noticed same and I don't know if I am doing something wrong since this is just a matter of connectinng drivers and digital panel meters.
No big visdom yet I can't figure out why is this behaving like so.
Anybody ?