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<== Date ==> <== Thread ==>

Subject: RE: Modbus help
From: "Mark Rivers" <[email protected]>
To: <[email protected]>, <[email protected]>
Date: Tue, 24 Nov 2009 11:32:01 -0600
Hi Emma,

Here are some questions/suggestions:

- Can you send your startup script?  
- How have you set the interpose interface, etc?  
- Does your device use serial/RTU (binary) or serial/ASCII protocol?  
- What is the slave address of your device?
- You have turned on asynTrace for the underlying asyn serial port.
Please also turn on asynTrace for the Modbus asyn port.  That should be
very helpful.

Once I know how it is configured I can figure out if those 8 characters
it is sending are correct.

Mark


-----Original Message-----
From: [email protected]
[mailto:[email protected]] On Behalf Of
[email protected]
Sent: Tuesday, November 24, 2009 10:52 AM
To: [email protected]
Subject: Modbus help

Hi,

I'm trying to get an RS-485 chain of N2300 temperature monitors talking
to EPICS using the asyn modbus support (R1-3) and so far am not having
much luck.  Basically I just get no response back from any of them,
although I'm pretty confident I'm sending out the right message (I
checked it with a serial analyser) and have configured the correct comms
setting.

After iocInit I get the following message on the console (with asynTrace
turned on):

2009/11/24 16:03:34.302 drvModbusAsyn::doModbusIO port readTemp is
disconnected

and then lots of I/O errors:

02 03 00 01 00 01 d5 f9
2009/11/24 16:03:38.952 drvModbusAsyn::doModbusIO port readTemp error
calling writeRead, error=, nwrite=5/5, nread=0
2009/11/24 16:03:39.302 ME02P-DI-TMON-01:TEMP1 devAsynFloat64::process
read error
2009/11/24 16:03:40.452 drvModbusAsyn::doModbusIO port readTemp has I/O
error
2009/11/24 16:03:40.452 /ty/72/0 write 8

02 03 00 01 00 01 d5 f9
2009/11/24 16:03:41.952 drvModbusAsyn::doModbusIO port readTemp error
calling writeRead, error=, nwrite=5/5, nread=0
2009/11/24 16:03:43.452 drvModbusAsyn::doModbusIO port readTemp has I/O
error
2009/11/24 16:03:43.452 /ty/72/0 write 8

....... etc

asynReport prints the following:

modbus port: readTemp
    asynOctet server:   ty_72_0
    modbusFunction:     3
    modbusStartAddress: 01
    modbusLength:       01
    plcType:            N2300
    I/O errors:         119
    Read OK:            0
    Write OK:           0
    pollDelay:          1.500000
    Time for last I/O   0 msec
    Max. I/O time:      0 msec
value = 0 = 0x0

Am I likely to be chasing a wiring/hardware issue here or is there
something standing out that indicates a problem higher up? This is the
first time I've tried to use modbus so I'm not sure what a 'working'
system looks like!

Thanks in advance,

Emma


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Replies:
RE: Modbus help emma.shepherd
References:
Modbus help emma.shepherd

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