Experimental Physics and
Industrial Control System

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

Subject:	modbus read error
From:	Дмитрий Прощенко via Tech-talk <tech-talk at aps.anl.gov>
To:	"tech-talk at aps.anl.gov" <tech-talk at aps.anl.gov>
Date:	Mon, 29 Mar 2021 20:13:08 +0700

Hi all, Im a student and a beginner in EPICS.

I am currently developing an IOC to drive a power supply (PS) via Modbus RTU. Using lib modbus R3-2.

I have a problem with DO reading, DO writing is successful. I can see, PS receives message and answers (what I dont know).

I thought there was a mistake in the argument in function in st.cmd, but I tested modbus start address and slave address in Modpoll.

Also asynReport was used, and according to it: ....name=IO_ERRORS, value=49,...... (depends on run time)

My error:

TEST-MSC-FUN:COIL-ONOFF-GET devAsynUInt32Digital::processCallbackInput process read error.

and sometimes:

drvModbusAsyn::doModbusIO port SET writeRead status back to normal having had 1 errors, nwrite=6/6, nread=5

What shout I pay attention to?

Its my db:

record (bi,"TEST-MSC-FUN:COIL-ONOFF-GET")

{

field(DESC, "Ctrl on/off PSU")

field(DTYP, "asynUInt32Digital")

field(INP, "@asynMask(GET 1 0x1) MODBUS_DATA")

field(ONAM, "ON")

field(SCAN, "1 second")

field(ZNAM, "OFF")

}

record (bo,"TEST-MSC-FUN:COIL-ONOFF-SET")

{

field(DESC, "ON OFF PSU")

field(DTYP, "asynUInt32Digital")

field(ONAM, "ON")

field(OUT, "@asynMask(SET 1 0x1)")

field(ZNAM, "OFF")

}

Its my st.cmd:

callbackParallelThreads

drvAsynSerialPortConfigure("PSU0", "/dev/ttyS1", 0, 0, 0)

asynSetOption("PSU0",0,"baud","57600")

asynSetOption("PSU0",0,"parity","none")

asynSetOption("PSU0",0,"bits","8")

asynSetOption("PSU0",0,"stop","1")

modbusInterposeConfig("PSU0",1,300,4)

# Function code=1

drvModbusAsynConfigure("GET", "PSU0", 1, 1, 0, 300, 0, 500, "PSU")

# Function code=5

drvModbusAsynConfigure("SET", "PSU0", 1, 5, 0, 128, 0, 1000, "PSU")

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ANJ, 29 Mar 2021