Experimental Physics and
Industrial Control System

"Meddage, Varuna via Tech-talk" <tech-talk at aps.anl.gov> · Thu, 20 Oct 2022 13:51:00 +0000

Hi,

I have question about extracting PV value from a bo type record in EPICS through an external C++ program.

If I explain the issue in detail,

First I created a bo type record in one of the .db files. Then I was able to successfully change the value of this record using CS - studio GUI using an on/off switch. (used ca_get command to confirm whether the PV value is changed, when I toggle the on/off switch in CSS GUI)

////////////////////////////////////////// This is the b0 type record in my .db file ///////////////////////

record(bo,"$(detector)_wib$(crate)0$(wib)_femb$(femb)/switch")

{

field(DTYP,"")

        field(OUT,"CA_LINK")

        field(SCAN,"Passive")

        field(DESC,"Status")

field(ZSV,"MAJOR")

field(OSV,"NO_ALARM")

field(ZNAM,"Off")

field(ONAM,"On")

}

//////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////

But when I try to extract the value of this PV through an external C++ program, using ca_get command, I cannot do that successfully.

/////////////////////////////////////////////////// rough outline of the C++ program used to extract PV value ///////////////

chid femb[N_FEMB_PV];

int status;

std::cout << "********************** FEMB sensor summmary ************************** \n";

for(int i=0; i<N_FEMB_PV; i++) {

     sprintf(femb_pv[i], femb_pv_pattern[i]);

     printf("%s\n", femb_pv[i]);

     status = ca_create_channel(femb_pv[i], NULL, NULL, 0, &femb[i]);

     SEVCHK(status,"ca_create_channel error");

     status = ca_pend_io(1.0);

     SEVCHK(status,"ca_pend_io error");

     printf("PV:    %s\n", ca_name(femb[i]));

     printf("State: %d\n", ca_state(femb[i]));

     printf("Host   %s\n", ca_host_name(femb[i]));

     printf("Read:  %d\n", ca_read_access(femb[i]));

     printf("Write: %d\n", ca_write_access(femb[i]));

     printf("Type:  %s\n", dbr_type_to_text(ca_field_type(femb[i])));

     printf("Count: %d\n", ca_element_count(femb[i]));

     printf("State: %d\n", ca_state(femb[i]));

}

double femb_power_commands[96];

for (int entry=0; entry<some_number; entry++){

  status = ca_get(DBR_DOUBLE,femb[entry],&femb_power_commands[entry]);

}

////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////

Any advice to solve this issue is really appreciated.

Thanks

Varuna Meddage

Experimental Physics and Industrial Control System

Experimental Physics and
Industrial Control System