Experimental Physics and
Industrial Control System

Paul Nord <[email protected]> · Thu, 21 Feb 2013 12:12:17 -0600

James,

Ah, you've tried to change too many things in the db file.  That text is actually formatting the snmpset/snmpget call and the expected text format/response.

In the case of the value you are looking at:
> WIENER-CRATE-MIB::outputVoltage.u0 = Opaque: Float: 4.500000 V

field(OUT, "@$(IP) guru WIENER-CRATE-MIB::outputVoltage.$(ch) 100 F")
Internally the driver is issuing a call much like the command line:
snmpset  -v 2c -m +WIENER-CRATE-MIB -c guru 192.168.1.100 outputVoltage.u0 F ###
The documentation from John Priller's site is excellent.

Paul

On Feb 21, 2013, at 10:41 AM, James F Ross <[email protected]> wrote:

> Hello everyone,
> As I mentioned in a previous email I'm trying to write an IOC that
> controls a wiener PL508 crate via snmp.  I have one that controls a
> PL512 crate and I'm trying to understand it so I can write an IOC for
> the PL508.
> 
> At the moment, I'm focusing on how the .db files get the information
> from snmp.  The following record is a good example:
> record(ai, "HFT:PXL:U$(Ch):GetDemandVoltage")
> {
>    field(DTYP,"asynFloat64")
>    field(INP,"@asyn($(IP) $(Ch) .1) Demand_Voltage")
>    field(SCAN,"5 second")
>    field(LINR,"LINEAR")
> }
> 
> Where Ch can be 0 through 11 and IP is the IP address of the crate.
> 
> I believe that the key is this field:
> field(INP,"@asyn($(IP) $(Ch) .1) Demand_Voltage")
> 
> This should correspond to one of the following variables (obtained via
> snmpwalk).  I think the first is most likely the variable that the
> field gets its input from.
> WIENER-CRATE-MIB::outputVoltage.u0 = Opaque: Float: 4.500000 V
> WIENER-CRATE-MIB::outputMeasurementSenseVoltage.u0 = Opaque: Float: 0.000000 V
> WIENER-CRATE-MIB::outputMeasurementTerminalVoltage.u0 = Opaque: Float:
> 0.000000 V
> 
> Does anyone know where a good guide to using asyn with snmp would be?
> Or perhaps a general epics/snmp guide?  I just need to know how
> "@asyn($(IP) $(Ch) .1) Demand_Voltage" points to outputVoltage.u0 and
> what I should put in other INP fields for other crate variables.
> 
> Thanks!
> James

Experimental Physics and Industrial Control System

Experimental Physics and
Industrial Control System