Re: Question about a tutorial wiritten by Norum

[Eric Norum <norume@aps.anl.gov>]

On Sep 30, 2008, at 11:14 AM, marco_hair wrote:

>  hi, Eric:
>
> I follow your tutorial, but seems there is sth. wrong in my test code.
> this is dbtr message:
>
> epics> dbtr AB300:FilterWheel:fbk
> ACKS: NO_ALARM      ACKT: YES           ADEL: 0             ALST: 0
> ASG:                BKPT: 0x00          DESC: Filter Wheel Position
> DISA: 0             DISP: 0             DISS: NO_ALARM      DISV: 1
> DTYP: AB300         EGU:                EVNT: 0              
> FLNK:CONSTANT 0
> HHSV: NO_ALARM      HIGH: 0             HIHI: 0             HOPR: 0
> HSV: NO_ALARM       HYST: 0             INP:GPIB_IO #L0 A0 @2
> LALM: 0             LCNT: 0             LLSV: NO_ALARM      LOLO: 0
> LOPR: 0             LOW: 0              LSV: NO_ALARM       MDEL: 0
> MLST: 0             NAME: AB300:FilterWheel:fbk             NSEV:  
> NO_ALARM
> NSTA: NO_ALARM      PACT: 1             PHAS: 0             PINI: NO
> PRIO: LOW           PROC: 0             PUTF: 0             RPRO: 0
> SCAN: Passive       SDIS:CONSTANT       SEVR: INVALID        
> SIML:CONSTANT
> SIMM: NO            SIMS: NO_ALARM      SIOL:CONSTANT       STAT: UDF
> SVAL: 0             TPRO: 0             TSE: 0               
> TSEL:CONSTANT
> UDF: 1              VAL: 0
> epics> 2008/10/01 00:11:33.540 192.168.1.103:4001 write 2
> ª\201
> epics> 2008/10/01 00:11:35.468 192.168.1.103:4001 read 4
> U\020\000\020
> 2008/10/01 00:11:37.465 AB300:FilterWheel:fbk convert failed Invalid  
> reply
>
> I change the code in devAB300.c like this:
>   {&DSET_LI, GPIBREAD, IB_Q_LOW, "\252\201\000\201", NULL, 0, 10,
>    convertCurrentReply, 0, 0, NULL, NULL, NULL},
>
> why can I only send 2 bytes to device through an Ethernet/serial box?

You've hit a shortcoming in the devGpib support.  The problem is with  
the string you're trying to send.  The devGpib code expects the  
command/format strings to be null-terminated and thus sees the '\000'  
in your command as the end of the string.
If there's no way to avoid sending the NUL character to instrument  
you'll have to specify GPIBCVTIO in the command table entry and  
perform all the I/O operations yourself in the custom conversion  
routine.

Here's a very simple example from device support for a MAX1619 digital  
thermometer.  As you can see, the 'read local temperature' command  
code (Param 2) is a NUL.

/*
 * Custom I/O routines
 */
static int
readRegisterValue(struct gpibDpvt *pdpvt, int P1, int P2, char **P3)
{
    struct longinRecord *pli = ((struct longinRecord *)(pdpvt- 
>precord));
    gpibCmd *pgpibCmd = gpibCmdGet(pdpvt);
    asynOctet *pasynOctet = pdpvt->pasynOctet;
    void *asynOctetPvt = pdpvt->asynOctetPvt;
    size_t ntrans;
    int eomReason;
    char reply;

    if ((pasynOctet->write(asynOctetPvt,pdpvt->pasynUser,pgpibCmd->cmd,
                                        1,&ntrans) != asynSuccess)
     || (pasynOctet->read(asynOctetPvt,pdpvt->pasynUser,&reply,
                                        1,&ntrans,&eomReason) !=  
asynSuccess)
     || (ntrans != 1)) {
        return -1;
    }
    if (P1)
        pli->val = (signed char)reply;
    else
        pli->val = (unsigned char)reply;
    pli->udf = 0;
    return 0;
}
.
.
.
.
    /* Param 0 -- Read manufacturer ID code */
    {&DSET_LI, GPIBCVTIO, IB_Q_LOW, "\xFE", NULL, 0, 1,
        readRegisterValue, 0, 0, NULL, NULL, NULL},

    /* Param 1 -- Read Device ID code */
    {&DSET_LI, GPIBCVTIO, IB_Q_LOW, "\xFF", NULL, 0, 1,
        readRegisterValue, 0, 0, NULL, NULL, NULL},

    /* Param 2 -- Read local temperature */
    {&DSET_LI, GPIBCVTIO, IB_Q_LOW, "\x00", NULL, 0, 1,
        readRegisterValue, 1, 0, NULL, NULL, NULL},

    /* Param 3 -- Read remote temperature */
    {&DSET_LI, GPIBCVTIO, IB_Q_LOW, "\x01", NULL, 0, 1,
        readRegisterValue, 1, 0, NULL, NULL, NULL},


--
Eric Norum <norume@aps.anl.gov>
Advanced Photon Source
Argonne National Laboratory
(630) 252-4793