Experimental Physics and
Industrial Control System

I did the experiment Mark suggested and found that drvModbusAsyn.c is working as
expected - it returns small negative integers when small negative voltages are applied to the converter.  BUT in those cases RVAL is still reported as a large positive integer.  Details follow:

On Sat, 12 Dec 2015, Mark Rivers wrote:

You could add the following printf statement to drvModbusAsyn.c::readPlcInt and see what the output is for that value.

       case dataTypeInt16:
       result = (epicsInt16)value;
printf("readPlcInt, offset=%d, value=0x%x, result=%d (0x%x)\n", offset, value, result, result);
       break;

I did that and got these results.  When Vin is a small positive value +0.002 V,
value is a small positive integer and RVAL is a small positive integer:

readPlcInt, offset=0, value=0x1, result=1 (0x1)

dbgf Iso:GantryCouch:Collimator:Actual.RVAL
DBR_LONG:           6         0x6

(the voltage varies slightly between the printf and dbgf outputs)

 readPlcInt, offset=0, value=0xfff4, result=-12 (0xfffffff4)

dbgf Iso:GantryCouch:Collimator:Actual.RVAL
DBR_LONG:           65524     0xfff4

So it seems RVAL is handled differently than value.  Is there some way to make
RVAL behave like value?

Jon Jacky

PS - here are answers to Mark's other questions about MODBUS_DATA and asynReport

In your database for the ai record what is the drvInfo field in the INP link? Is it still MODBUS_DATA? If so, that should be fine.

Yes, dbpr reports the INP field is INP:INST_IO @asynMask(CollimCouch, 0, 16, 1000)MODBUS_DATA

Please send the output of the following command:

asynReport(1, "CollimCouch")

I believe addr 0 is connected to Vin in the output shown above.

epics> asynReport(1, "CollimCouch")
CollimCouch multiDevice:Yes canBlock:Yes autoConnect:Yes
    enabled:Yes connected:Yes numberConnects 1
    nDevices 6 nQueued 0 blocked:No
    asynManagerLock:No synchronousLock:No
    exceptionActive:No exceptionUsers 0 exceptionNotifys 0
    traceMask:0x1 traceIOMask:0x0 traceInfoMask:0x1
    addr 0 autoConnect Yes enabled Yes connected No exceptionActive No
        exceptionActive No exceptionUsers 0 exceptionNotifys 0
        blocked No
        traceMask:0x1 traceIOMask:0x0 traceInfoMask:0x1
    addr 5 autoConnect Yes enabled Yes connected No exceptionActive No
        exceptionActive No exceptionUsers 0 exceptionNotifys 0
        blocked No
        traceMask:0x1 traceIOMask:0x0 traceInfoMask:0x1
    addr 3 autoConnect Yes enabled Yes connected No exceptionActive No
        exceptionActive No exceptionUsers 0 exceptionNotifys 0
        blocked No
        traceMask:0x1 traceIOMask:0x0 traceInfoMask:0x1
    addr 4 autoConnect Yes enabled Yes connected No exceptionActive No
        exceptionActive No exceptionUsers 0 exceptionNotifys 0
        blocked No
        traceMask:0x1 traceIOMask:0x0 traceInfoMask:0x1
    addr 2 autoConnect Yes enabled Yes connected No exceptionActive No
        exceptionActive No exceptionUsers 0 exceptionNotifys 0
        blocked No
        traceMask:0x1 traceIOMask:0x0 traceInfoMask:0x1
    addr 1 autoConnect Yes enabled Yes connected No exceptionActive No
        exceptionActive No exceptionUsers 0 exceptionNotifys 0
        blocked No
        traceMask:0x1 traceIOMask:0x0 traceInfoMask:0x1
modbus port: CollimCouch
    asynOctet server:   AcromagCollimCouch
    modbusSlave:        0
    modbusFunction:     4
    modbusStartAddress: 00
    modbusLength:       011
    plcType:            AcromagXT1221
    I/O errors:         0
    Read OK:            2207
    Write OK:           0
    pollDelay:          0.100000
    Time for last I/O   1 msec
    Max. I/O time:      7 msec
    Time per hist. bin: 1 msec

Replies:

Re: ai RVAL via asyn + modbus: getting unsigned integer Mark Rivers

RE: ai RVAL via asyn + modbus: getting unsigned integer Mark Rivers

References:

RE: ai RVAL via asyn + modbus: getting unsigned integer Mark Rivers

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