RE: CRC issues using Modbus/asyn on 64bit Linux

[Vesna Samardzic-Boban <Vesna.Samardzic-Boban@synchrotron.org.au>]

Hi Mark,

Can confirm I have used modbus/asyn without bad CRC generated by a serial RTU.(a neutron radiation monitor BDKN-01), but on 32-bit linux.

Although I had to do some changes because the device itself was not in accordance with the standard i.e.
it had CRC bytes swapped! So I modified the modbus driver to accomodate this, also had to add some delays in the asyn interface (again the device's weakness because it did not follow time insertion recommendations from the standard).
After that had no CRC errors and it worked.  

Vesna

________________________________________
From: tech-talk-bounces@aps.anl.gov [tech-talk-bounces@aps.anl.gov] On Behalf Of Mark Rivers [rivers@cars.uchicago.edu]
Sent: Friday, 2 March 2012 9:13 AM
To: Emma Shepherd; 'Ralph Lange'; EPICS Tech Talk
Subject: RE: CRC issues using Modbus/asyn on 64bit Linux

Folks,

I would like to figure out if this is a problem with bad CRC being generated by the devices, or whether my code is incorrectly computing the CRC on the received message.

Can anyone report whether they are using Modbus/asyn with serial RTU without getting CRC error messages?  If so, then it would seem like Emma and Ralph have devices that are generating an incorrect CRC.  But if everyone is getting errors then the problem is likely in my driver.

I don't have any serial RTU devices I can use for testing.  However, when I originally wrote the driver I did buy some inexpensive Modbus server emulation software, and the driver worked OK including CRC with serial RTU and LRC with serial ASCII.

Mark


-----Original Message-----
From: Emma Shepherd [mailto:Emma.Shepherd@synchrotron.org.au]
Sent: Thursday, March 01, 2012 3:54 PM
To: Mark Rivers; 'Ralph Lange'; EPICS Tech Talk
Subject: RE: CRC issues using Modbus/asyn on 64bit Linux

Hi Mark,

I've had a similar experience with a chain of West 2300 temperature monitors (also serial RTU on RS-485).  In my case the IOC was running on vxWorks, but like Ralph I was seeing persistent modbus CRC errors on the IOC console, although the data itself was good.  I thought it was probably something wrong in my setup but didn't have time to do much investigation.

Emma



-----Original Message-----
From: tech-talk-bounces@aps.anl.gov [mailto:tech-talk-bounces@aps.anl.gov] On Behalf Of Mark Rivers
Sent: Friday, 2 March 2012 4:47 AM
To: 'Ralph Lange'; EPICS Tech Talk
Subject: RE: CRC issues using Modbus/asyn on 64bit Linux

I should add that the CRC is only used on Modbus serial RTU, not on Modbus TCP or Modbus serial ASCII.

So 2 questions:

1) Has anyone successfully run Modbus/asyn serial RTU on 64bit Linux?

2) Has anyone run the Wave P6100 temperature controller with Modbus/asyn serial RTU on any architecture?

Mark


-----Original Message-----
From: tech-talk-bounces@aps.anl.gov [mailto:tech-talk-bounces@aps.anl.gov] On Behalf Of Ralph Lange
Sent: Thursday, March 01, 2012 11:30 AM
To: EPICS Tech Talk
Subject: CRC issues using Modbus/asyn on 64bit Linux

Hi,

I am reliably getting CRC errors on the device's answer when reading
more than two parameters (Modbus code 3) through serial RTU on RS-485
from a Wave P6100 temperature controller. The data itself looks good and
reasonable.
One or two word access (Modbus code 1 or 3) seems to work fine.
The IOC runs on 64bit Linux, using Mark Rivers' Modbus on ASYN driver.
(All from synApps 5.5)

Has anyone seen similar behaviour?
Does anyone successfully run Modbus/asyn on 64bit Linux? (To rule out 64
bit issues in the CRC checking part.)

Thanks for any help,
~Ralph

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