Experimental Physics and
Industrial Control System

Benjamin Franksen <[email protected]> · Sun, 12 May 2013 18:42:42 +0200

Am Donnerstag, 9. Mai 2013, 21:20:00 schrieb Joe Sullivan:
> SNC evflags used to be made available to escaped C code via #define
>
> ---------------------------------------------------------------------
> /* SNC Version 2.0.12: Wed Jun 16 13:13:56 2010: batch_scan_v3.i */
> /* Event flags */
> #define updateTime    1
> #define modeChange    2
> #define positioner1Done       3
> #define positioner2Done       4
> #define positioner3Done       5
> ---------------------------------------------
>
> Now the 'enums' are defined in-line in sequence code but not in
> escaped C functions where they become undefined variables.
>
> # line 2107 "../batch_scan_v3.st"
>                               seq_efSet(ssId, 3/*positioner1Done*/);
>
> Was this done on purpose?

It is always fascinating what uses people find for stuff once it exists...

I simply did not imagine that use case! The change was done simply to bring
event flags in line with how variables are treated (which you cannot directly
use in embedded C code for similar reasons).

Obviously that was flawed thinking on my part. Because for variables there is
pvIndex function, which unfortunately refuses to work with event flags. But
this is actually not a big problem, because you can just leave it off, see
below.

> What is the best way around this?

There is indeed a trick which works: you pass the event flag to your C
function as a value of type EV_ID (which is a synonym for 'unsigned' but that
need not concern you):

program event_flag_in_c_func

evflag x;

%{
static void efSet_x(SS_ID ssId, EV_ID x)
{
    seq_efSet(ssId, x);
}
}%

/* call the C function from SNL code: */

ss myss {
    state set_flag {
        when () {
            efSet_x(ssId, x);
        } state check_flag
    }
    state check_flag {
        when (delay(0.5)) {
            printf("oops, timeout, didn't work\n");
        } exit
        when (efTest(x)) {
            printf("cool, we came here, means it worked\n");
        } exit
    }
}

Cheers
--
Ben Franksen
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Experimental Physics and Industrial Control System

Experimental Physics and
Industrial Control System