Re: About errors in controlling the motor controller.

[Mark Rivers via Tech-talk <tech-talk@aps.anl.gov>]

Hi White,

• the vendor said that the addresses need to be incremented by one

That is probably not true for the EPICS driver.  There is a convention I never understood where some Modbus software uses addresses that are 1 bigger than the physical address.  But the EPICS driver uses the physical address, so you should use the addresses shown in the spreadsheet.

• drvModbusAsynConfigure("0X1R","CAT2",1,5,1,10,0,100,"CAT2") 

That means:

• Port name of asyn driver is "0X1R"
• Port name of TCP driver is "CAT2"
• Slave address = 1
• Modbus function = 5,  write single coil
• Modbus start address = 1
• Modbus length = 10
• Modbus data type = 0 = INT16
• Poll ms = 100
• PlcType = "CAT2"

I think you need to change this to Modbus start address to 0, not 1.  

You have set the SCAN field of the bo record to I/O Intr.  That is not correct that is only for input records.  It should be Passive, which is the default, so you can omit that field.

Did you check for error messages on the IOC console?

You can try processing that record and see more details about the record with this command:

dbtr FMC01:HOMING_TRIGGER 2

Mark

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From: Tech-talk <tech-talk-bounces@aps.anl.gov> on behalf of White via Tech-talk <tech-talk@aps.anl.gov>
Sent: Friday, November 28, 2025 3:17 AM
To: tech-talk@aps.anl.gov <tech-talk@aps.anl.gov>
Subject: About errors in controlling the motor controller.

 

Hi，

I am using EPICS to remotely control a stepper motor controller (IP: 192.168.0.11), which supports the Modbus-TCP protocol. I want to use the homing trigger function for axis 0. My st.cmd file and db file are as follows, and it runs without errors. but the PV does not connect successfully. The same situation applies to relative motion and absolute motion commands.the Modbus addresses are in the attachment, ( the vendor said that the addresses need to be incremented by one)

 

drvAsynIPPortConfigure(“CAT2”,”192.168.0.11:502”,0,0,0)

modbusInterposeConfig("CAT2",0,2000,0)

drvModbusAsynConfigure("0X1R","CAT2",1,5,1,10,0,100,"CAT2")

 

record(bo, "$(DEVNAME):HOMING_TRIGGER")

{

field(DTYP, "asynUInt32Digital")

field(OUT, "@asynMask(0X1R 1 0x1)")

field(ZNAM,"0")

field(ONAM,"1")

field(SCAN, "I/O Intr")

}

When I enter dbpr, it displays as follows:

epics> dbpr FMC01:HOMING_TRIGGER

ASG :               DESC:               DISA: 0             DISP: 0             

DISV: 1             NAME: FMC01:SEARCH_0_TRIGGER            RBV : 0             

RVAL: 0             SEVR: INVALID       STAT: UDF           TPRO: 0             

VAL : 0

 

 Did I make a mistake somewhere?

 

Thanks

White