Re: A problem with modbus reading floating point numbers

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

Hi Gao,

I think I see the problem:

file "../../db/ai.template" { pattern
{P,         R,      PORT,               OFFSET, BITS,  EGUL,  EGUF,   PREC,   SCAN}
{MOXA:,    ADC1,   MOXA_E1242_In_Word,   0,      16,   0.,    65535.,    3,      "I/O Intr"}
{MOXA:,    ADC2,   MOXA_E1242_In_Word,   1,      16,   0.,    65535.,    3,      "I/O Intr"}
}

You have set EGUF to 65535.  If you do that then the ai record will do a linear conversion, but the output values in EGU units will be the same as the input values in RAW units.  You should set the EGUF to be the maximum value of the ADC in the engineering units you want to use.  For example, if it is a 0 to 10V ADC then you can set EGUF=10 and then the ai record will be in the units of volts.  If it is -10V to 10V ADC you should set EGUL=-10.

Mark

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From: 高振华 <gaozh at ihep.ac.cn>
Sent: Wednesday, November 17, 2021 2:36 AM
To: Mark L Rivers <rivers at cars.uchicago.edu>
Cc: tech-talk at aps.anl.gov <tech-talk at aps.anl.gov>
Subject: A problem with modbus reading floating point numbers

 

Hi Mark,

I am reading the ai value of moxa E1242 multifunctional IO module and I have a problem,

Cannot display floating point numbers, only integer numbers, 

cannot display decimal places.

What's the reason? thanks.

#moxa1242.cmd
#!./../../bin/linux-x86_64/modbusApp
< envPaths
dbLoadDatabase("../../dbd/modbus.dbd")
modbus_registerRecordDeviceDriver(pdbbase)
drvAsynIPPortConfigure("moxa","192.168.127.254:502",0,0,1)
asynSetOption("moxa",0, "disconnectOnReadTimeout", "Y")
modbusInterposeConfig("moxa",0,5000,0)
#read moxa E1242 AI_scaledValue,7 is little endian,8 is big endian
drvModbusAsynConfigure("MOXA_E1242_In_Word",   "moxa",    255, 4,  0x208,  0x8,    0x7,  2000,    "moxa E1242")
# Enable ASYN_TRACEIO_HEX on octet server
asynSetTraceIOMask("moxa",0,4)
# Enable ASYN_TRACE_ERROR and ASYN_TRACEIO_DRIVER on octet server
asynSetTraceMask("moxa",0,9)
dbLoadTemplate("moxa1242.substitutions")
iocInit
asynReport 1
dbl

#moxa1242.substitutions
#asyn record for the underlying asyn octet port
file "$(ASYN)/db/asynRecord.db" { pattern
{P,           R,       PORT,      ADDR,   IMAX,    OMAX}
{MOXA:    OctetAsyn,    moxa,     0,      80,      80}
}
file "../../db/ai.template" { pattern
{P,         R,      PORT,               OFFSET, BITS,  EGUL,  EGUF,   PREC,   SCAN}
{MOXA:,    ADC1,   MOXA_E1242_In_Word,   0,      16,   0.,    65535.,    3,      "I/O Intr"}
{MOXA:,    ADC2,   MOXA_E1242_In_Word,   1,      16,   0.,    65535.,    3,      "I/O Intr"}
}

#ai.template
record(ai, "$(P)$(R)_AI") {
    field(DTYP,"asynInt32")
    field(INP,"@asynMask($(PORT) $(OFFSET) $(BITS))MODBUS_DATA")
    field(LINR,"LINEAR")
#    field(LINR,"NO CONVERSION")
    field(EGUL,"$(EGUL)")
    field(EGUF,"$(EGUF)")
    field(HOPR,"$(EGUF)")
    field(LOPR,"$(EGUL)")
    field(PREC,"$(PREC)")
    field(SCAN,"$(SCAN)")
}

#traceIO
2021/11/17 15:41:17.075 192.168.127.254:502 write 12

01 17 00 00 00 06 ff 04 02 08 00 08 
2021/11/17 15:41:17.083 192.168.127.254:502 read 25

01 17 00 00 00 13 ff 04 10 13 b0 40 f0 00 00 00 00 00 dc 3b 
5c 00 a0 3b a0 

#caget display
[gaozh@localhost db]$ caget MOXA:ADC1_AI
MOXA:ADC1_AI                   7
note:The actual input is 7.5V.

application environment:
EPICS 7.0.3
Asyn R4-33
Modbus R2-11

Thanks,
Gao Zhenhua

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BSRF(Beijing Synchrotron Radiation Facility)
Email:gaozh at ihep.ac.cn