Seems to me like the problem happens less frequently, but I still see it (1 out of 5 or so). The fact that /Sequencer/Params/Value is empty tells me that the GUI 
has the problem and not the sequencer side.

Stefan

Indeed there was a sleep(100ms) in the sequencer in each loop. I reduced it now to 10ms. I need at least 10ms since otherwise 
the sequencer would run in an infinite loop during the wait and burn 100% CPU. The smallest time slice on Linux to sleep is 
10ms, so that's why I set it to that. Give it a try.

Stefan

Actually I realized that a 1ms wait still works, so I reduced it to that.

Stefan

This is a common problem I also encountered in the past. You get a low-level ODB access error (could also be a read of a non-existing key) and you 
have no idea where this comes from. Could be the alarm system, a mhttpd web page, even some user code in a front-end over which the midas library 
has no control.

One option would be to add a complete stack dump to each of these error (ROOT does something like that), but I hear already people shouting "my 
midas.log is flooded with stack dumps!". So what I do in this case is I run a midas program in the debugger and set a breakpoint (in your case at 
odb.cxx:6967). If the breakpoint triggers, I inspect the stack and find out where this comes from.

Not that I print a stack dump for such error in the odbxx API. This goes to stdout, not the midas log, and it helped me in the past. Unfortunately 
stack dumps work only under linux (not MacOSX), and they do not contain all information a debugger can show you.

It is not true that alarm conditions are evaluated when the alarm system is off. I just tried and it works fine. The code is here:

alarm.cxx:591

      /* check global alarm flag */
      flag = TRUE;
      size = sizeof(flag);
      db_get_value(hDB, 0, "/Alarms/Alarm system active", &flag, &size, TID_BOOL, TRUE);
      if (!flag)
         return AL_SUCCESS;

so no idea why you see this error if you correctly st "Alarm system active" to false.

Stefan

For everybody using EPICS: There is now a new system called MSetPoint (Midas Set Point) to control whole beamlines via EPICS.
It's under midas/msetpoint and the documentation is here:

   https://bitbucket.org/tmidas/midas/wiki/MSetPoint

It is basically an EPICS frontend and two custom pages. The special thing is that the EPICS elements are not hardcoded in
the frontend but come from the ODB. There is even an editor for the beamline elements (second custom page). By loading different
ODB settings, one can switch easily between completely different beamlines without having to recompile the frontend. The system
can be operated standalone (all other MIDAS pages do not appear), or as a custom page in a normal midas setup. At PSI, this
system is now used as the standard editor for our beamlines.

Attached and example screen.

Stefan

For everybody using EPICS: There is now a new system called MSetPoint (Midas Set Point) to control whole beamlines via EPICS.
It's under midas/msetpoint and the documentation is here:

   https://bitbucket.org/tmidas/midas/wiki/MSetPoint

It is basically an EPICS frontend and two custom pages. The special thing is that the EPICS elements are not hardcoded in
the frontend but come from the ODB. There is even an editor for the beamline elements (second custom page). By loading different
ODB settings, one can switch easily between completely different beamlines without having to recompile the frontend. The system
can be operated standalone (all other MIDAS pages do not appear), or as a custom page in a normal midas setup. At PSI, this
system is now used as the standard editor for our beamlines.

Attached and example screen.

Stefan

Taht's strange. I always was under the impression that .odb files are loaded relatively to the current location in 
the ODB. The behaviour should not be different for different data formats, so I agree to change the .odb loading to 
behave like the .xml and .json save/load.

Stefan

I fixed that and committed the change to megon02, just reload your browser. I also set ymin and ymax of the Vacuum plot to meaningful 
values (not to zero!).

Stefan

> I noticed that a check was added to mfe.cxx in 1961af0d6:
> 
> +      /* check for consistent common settings */
> +      if ((eq_info->read_on & RO_STOPPED) &&
> +          (eq_info->eq_type == EQ_POLLED ||
> +           eq_info->eq_type == EQ_INTERRUPT ||
> +           eq_info->eq_type == EQ_MULTITHREAD ||
> +           eq_info->eq_type == EQ_USER)) {
> +         cm_msg(MERROR, "register_equipment", "Events \"%s\" cannot be read when run is stopped (RO_STOPPED flag)", equipment[idx].name);
> +         return 0;
> +      }
> 
> 
> Can someone explain the purpose of this check and error message? Perhaps it
> was put in place with only DAQ FEs, not SC FEs in mind? And should the 
> documentation in the wiki actually be "s/Before stopping run/While run is stopped/"?

Indeed you have two types of events handled by mfe.cxx: Slow control events (EQ_SLOW or EQ_PRIODIC) and triggered events (EQ_POLLED or 
EQ_INTERRUPT or EQ_MULTITHREAD or EQ_USER). For slow control events it can make sense to read them also when the run is stopped, that's why you 
can specify RO_STOPPED or RO_ALWAYS. This does however not make sense for triggered events. Reading triggered events when the run is stopped 
invalidates the concept of runs (= read triggered events only during a run). We had cases where people mixed this up, so the warning was added. 
If you have a slow control event you want to read when the run is stopped, make sure it is of type EQ_SLOW or EQ_PERIODIC.

Stefan

I don't see any bad side effects at the moment, so I accepted the changes and committed them.

Stefan

We are considering to remove the analyzer framework mana.cxx from MIDAS. It 
currently has some compiler warnings and we wonder if we should fix them which 
would take some time or just remove the file. We have now to much more modern 
analyzer frameworks "manalyzer" and "ROOTANA" which should be used instead.

Is anybody still using the mana.cxx framework?

/Stefan

This request came more than once in the past. One thing I could implement is a "atexit" function similarly to the C funciton atexit().

Then we would have a function in the script which gets called whenever one does "stop immediately". This function can then restore
some ODB values or do whatever is necessary. 

If the sequencer gets killed in the middle, it can safely be restarted since the complete sequencer state is kept in the ODB under
/Sequencer/State. After the restart, the sequencer continues exactly where it has been killed before.

Would that solve your problem?

Stefan

Ok, no relevant complains so far, so I removed mana and rmana from the CMake build 
process, but left the file mana.cxx still in the repository for educational 
purposes ;-)

Stefan

> Hi,
> 
> I am writing a Rust based midas file reader however it was kind of hard to understand the full midas file 
> structure from the documentation.
> 
> Only at the end of the page 
> https://daq00.triumf.ca/MidasWiki/index.php/Event_Structure#MIDAS_Format_Event one finds under the 
> headline “tape format” that there are special events which mark the start and the end of the run. It would 
> be better to place this information more prominent maybe we a headline: “Special Events”. Maybe a link to 
> this section at the top of the page could help. Also at the mlogger page there is no information about this.
> 
> Best,
> Marius

Ben was so kind to update the event documentation:

  https://daq00.triumf.ca/MidasWiki/index.php/Event_Structure

Please have a look and let us know if that's better now.

Best,
Stefan

I had two free afternoon and took the opportunity to write a new API for the MSCB 
system. I'm not sure if anybody else actually uses MSCB (MIDAS slow control bus), 
but anyhow. 

The new API is contained in a single header file mscbxx.h, and it's extremely 
simple to use. Here is some example code:

#include "mscbxx.h"

...
   // connect to node 10 at submaster mscb123
   midas::mscb m("mscb123", 10);

   // print node info and all variables
   std::cout << m << std::endl;

   // refresh all variables (read from MSCB device)
   m.read_range();
   
   // access individual variables
   float f = m[5];   // index access
   f = m["In0"];     // name access

   // write value to MSCB device
   m["In0"] = 1.234;
...


Any feedback is welcome.

Stefan

> First the general advice: if you reduce the "period" of your equipment, then your function will get called more frequently. 
> You can set it to 0 and we'll call it as often as possible. You can set this in the ODB at "/Equipment/Python Data Simulator/Common/Period"

Just for your general understanding: The "period" i the C framework works differently. It calls the poll function with a number, 
and then that number is used in the poll function like (simplified):

poll(INT count) {
   for (i=0 ; i<count ; i++)
      if (new_event())
         return TRUE;
   return FALSE;
}

This ensures that polling is done as quickly as possible, even staying in the same function (poll) rather than called from the 
framework in a loop (which would require a function call to poll each time). The "count" is determined from the framework
during startup of the framework such that the execution time of the poll() routine equals the "period". Like if the period 
is 0.1, the count might be a few millions, so that the poll routine returns immediately when a new event occurs or when
100ms have expired. During the polling the frontend is "dead" meaning it cannot react on run transitions for example. That's
why most experiments use 0.1-0.5 seconds. But this does then NOT mean that you can only have 10-2 events per second, but that
the reaction time if the frontend is at maximum 0.1-0.5 seconds which is acceptable most of the case. 

Due to this design, the C frontend is capable of producing millions of events per second. It took me some while in the early 1990's
to work out that scheme sitting in the "R" trailer at TRIUMF (old guys will remember...).

Best,
Stefan