Experimental Physics and
Industrial Control System

Marty Kraimer <[email protected]> · Mon, 24 Jun 2002 07:47:53 -0500

Someone else asked for this feature. I think the first person to ask was Timo
Korhonen (SLS) who is also the person who is redoing drvTS, which is the support
for hardware generated time stamps.

The next version of base (both 3.13 and 3.14) will provide this feature. The
exact method is still undecided. Corrently in my working area I have the
following change to recGbl.c

For 3.13

void recGblGetTimeStamp(void* prec)
{
    struct dbCommon* pr = (struct dbCommon*)prec;

    if(pr->tsel.type!=CONSTANT)
        dbGetLink(&(pr->tsel), DBR_SHORT,&(pr->tse),0,0);
    if(pr->tse!=-1)
        TSgetTimeStamp((int)pr->tse,(struct timespec*)&pr->time);
}

For 3.14 I have

void epicsShareAPI recGblGetTimeStamp(void* prec)
{
    struct dbCommon* pr = (struct dbCommon*)prec;
    int status = 0;

    if(pr->tsel.type!=CONSTANT)
        dbGetLink(&(pr->tsel), DBR_SHORT,&(pr->tse),0,0);
    if (pr->tse!=-1)
        status = epicsTimeGetEvent(&pr->time,(unsigned)pr->tse);
    if(status) errlogPrintf("%s recGblGetTimeStamp failed\n",pr->name);
}

The above change says that if TSE=-1 then dont do anyting to the time stamp.

This is NOT the final answer however. David Thompson (SNS) pointed out that the
existing drvTS already treats TSE=-1 as a special case. It means that drvTS
should get the most accurate current time stamp. For example with the APS
hardware time stamp support, we keep a 1 millisecond hardware generated clock.
If TSE=-1 then the time stamp will be taken from this clock rather than the
vxWorks 60 HZ clock.

Thus the above change to recGblGetTimeStamp is not correct. David suggested that
we define.

#define epicsTimeEventBestTime -1
#define epicsTimeEventDeviceTime -10000

epicsTimeEventBestTime would be used by drvTS and it's successor.
epicsTimeEventDeviceTime says that device support is supplying the time stamp so
recGblGetTimeStamp should not do anything.

Questions to be resolved

1) Where do we define these? For 3.14 the obvious place is epicsTime.h. For 3.13
it is probably tsDefs.h

2) What value should we use for epicsTimeEventDeviceTime?

3) Whoever set the value for TSE must know about these values. How do we make
these values known? Just document them in the Application Developer's Guide?

Noboru Yamamoto wrote:

> Hi,
> 
> [Question]
> 
> Is there any good way to set a timestamp of a record while a
> process() function of a device support routine is called?
> 
> [Why I'm asking this question]
> 
> We need to import live data from the facility control
> system, which uses a proprietary control system. This system
> update the information on the memory periodically with
> theire own timestamp. We would like to use
> this timestamp as a timestamp of EPICS records rather than
> the timestamp when the record is updated.
> 
> Looking at aiRecord.c, for example, recGblGetTimeStamp is
> called AFTER a call to read() function in a device support
> is finished.
> 
> Any idea?
> 
> Noboru
> 
> 

Experimental Physics and Industrial Control System

Experimental Physics and
Industrial Control System